Sports floor

Abstract

The sports floor (1) comprises: a tread layer (2) comprising at least one layer of elastomeric material; and a support layer (3) comprising at least one layer of elastomeric material wherein the support layer (3) has a first arrangement of cavities with an elliptical cross-section (5).

Description

TECHNICAL FIELD

[0001] Sports flooring, for example for making athletic tracks, forms the subject of the present disclosure. BACKGROUND

[0002] Documents such as EP-0913524, EP-1096080 or EP-2055833, filed in the name of the present applicant, describe sports flooring comprising a tread layer consisting of an elastomeric mass and a support layer also consisting of an elastomeric mass. The support layer has support ribs of various natures on its lower side, i.e. the side opposite the tread layer.

[0003] For many years, flooring of the type specified above has been widely used in places for sports activities, such as sports fields, sports grounds and gymnasiums.

[0004] The above flooring is made, for example, starting from an elastomeric mixture, through one or more operations of mixing, extrusion and cascade calendering. In this way, it is possible to impart to the top surface of the tread layer a pattern of overall undulations, in which the reliefs mainly perform an anti-slip function for the top surface and a shock-absorbing function for the lower side.

[0005] In the solution described in document EP-0913524, the lower side of the flooring is provided with transverse ribs, inclined with respect to the tread layer, and connected together by longitudinal ribs, which are substantially formed like bridges connecting adjacent transverse ribs. By adopting a non-uniform network comprising two different types of ribs, it is possible to produce a flooring that presents a compliance characteristic, generally understood in the sense of elastic type resilience, which is differentiated according to the direction of running on the flooring.

[0006] Furthermore, in the solution described in document EP-1096080, the support layer comprises ribs inclined with respect to the tread layer. These inclined ribs, arranged in pairs, jointly form a suction anchor structure for the flooring. The inclined ribs contribute, in a globally marginal extent, to the characteristic of elastic compliance and therefore to the function of support for the flooring. Alternatively, this function is mainly assumed by other ribs extending in a substantially longitudinal direction with respect to the tread layer.

[0007] With reference to sports flooring for running, the terms "transverse" and "longitudinal" are intended to refer to the direction of running on the flooring. As the flooring in question is generally produced in the form of a sheet wound into a roll, the direction of running can be identified in a unique manner. The sheet is successively unwound on the flooring along the "longitudinal" direction, i.e. along the direction of their length or elongation, with the longitudinal direction of the sheet extending exactly along the direction of running. This direction also generally corresponds to the direction in which the calendering operation is performed.

[0008] The solution forming the specific subject of the documents EP-0913524 and EP-1096080 is therefore characterized in that the cavities provided on the lower side of the support layer are delimited by ribs which constitute a non-homogeneous (or non-uniform) mesh with different functions (support ribs / anchoring ribs) and / or with different characteristics complying with standards.

[0009] Over the years, instruments and procedures have been developed which enable the precise quantitative qualification of the characteristics of the floor of the type described above. The standard EN 14877 prescribes the methods and parameters and defines the specifications for surfaces for outdoor sports facilities. The standard EN 14904 specifies and discusses surfaces for indoor multiple sports.

[0010] In particular, the standard EN 14808 enables the definition of a parameter which characterizes the behavior of the floor in percentage terms, substantially corresponding to the behavior exhibited by a rigid surface subjected to the same pressure when a standard-sized weight falls on it, i.e. the "force reduction" (FR).

[0011] Floors designed for use in sports activities have FR values comprised between 25% and 50%; in particular, a track according to the EN 14877 standard has FR values comprised between 25% and 34% or between 35% and 50%, and a track for high-level competitions complying with the rules of the International Association of Athletics Federations (IAAF) has values comprised between 35% and 50%.

[0012] As regards the pressure due to the tread or run, the lower limit corresponds to a floor which can be characterized as "harder", while the upper limit corresponds to a "softer" floor.

[0013] As regards the requirements for surfaces for sports activities, the safety and protection of athletes from injuries during training and competition events are particularly important. For example, the rules of the International Association of Athletics Federations recommend that the synthetic surfaces of training sites should have, in general, a higher shock absorption than the sites where competitions are held. The surface is then characterized by other technical features, such as abrasion, hardness, maximum strength and relative elongation at break, as well as tear strength, which make it possible to exhibit the wear phenomena of the track and the resistance of the surface to the pressure exerted by the spikes of the shoes of the athletes.

[0014] The overall quality of the surface of a floor for athletics, understood as the optimal interaction between the athlete and the surface, depends on the combination of all these characteristics. The way in which the interaction takes place can differ not only according to the sports activity being carried out, but also according to the running style of each individual athlete. The interaction between the foot of the athlete and the track on which he or she runs not only takes place in the longitudinal direction, i.e. in the direction of the run, but also implies a transverse "rolling" movement, which corresponds to the rotational movement of the sole from the fifth metatarsal to the first metatarsal in a vertical plane transverse to the direction of the run.

[0015] Again, although the "soft" floor can be considered by some athletes as a "gentle" floor, softness should not be considered as a penalty for the athlete in terms of, for example, explosive force, which would instead lead to a tendency to a rather hard track, since within the range of values accepted by the standard there is no direct correlation between the FR value and the propulsion force transmission exerted by the athlete on the ground. Instead, it is proven that the uniformity of the behavior of the track is particularly important, since any lack of surface uniformity forces the athlete to correct his or her own track movement, with the result of an efficiency loss.

[0016] Document EP2055833 discloses a floor of the type described above, in which the support layer has a series of cavities delimited by ribs, which form a network of ribs distributed according to a uniform pattern. The cavities are cavities with an elongated shape, whose main dimension is aligned with the direction of running on the floor, and in one embodiment it occupies a volume equal to at least 28-30% of the volume of the support layer, a value that makes the floor rather "soft". The elongated shape of each cavity (for example, consisting of an irregular hexagon or rhombus in plan view) is oriented with the main dimension aligned with the direction of running on the floor means that the softness described above is present mainly in a direction transverse to the direction of running, thus - in an acceptable way for the athlete - facilitating the rolling movement described above, without cancelling the desired greater rigidity characteristic, which thus favors the exertion of explosive force by the athlete in the direction of running. The solution described in EP2055833 makes it possible to obtain better results in terms of performance than those achieved with the floors previously generally adopted, which typically have cavities of rectangular shape, using a floor in which the support layer has a network of uniform ribs.

[0017] However, at the same time, the floor mentioned above can present drawbacks, for example when the volume of the cavities present in the support layer undergoes variations. This situation can occur, for example, during the installation of such a floor; the glue used to bond the floor to the surface can fill part of the cavities, thus altering the FR value in a way that can sometimes not be foreseen.

[0018] For the purpose of obtaining a new generation of high-performance surfaces for sports activities with performance levels higher than those of known floors, the current main focus is to make an improved solution that enables the floor to be made in such a way that the FR value remains constant regardless of the production and / or installation conditions. SUMMARY

[0019] The aim of one or more embodiments of the present disclosure is to provide a sports floor that includes structural features that are able to overcome the above-mentioned drawbacks.

[0020] According to one or more embodiments, the above aim is achieved by a floor having the characteristics mentioned in the subsequent claims, which are understood to form an integral part of the present description.

[0021] Embodiments of the present disclosure provide a sports floor comprising a tread layer comprising at least one layer of elastomeric material; and a support layer comprising at least one layer of elastomeric material, wherein the support layer comprises a first arrangement of cavities with an elliptical cross-section. The present disclosure further provides a track and field runway, in particular for running, provided with a floor according to embodiments of the present description. BRIEF DESCRIPTION OF DRAWINGS

[0022] One or more embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings in which:

[0023] - Figure 1 is a perspective view of a portion of a floor according to embodiments of the present disclosure;

[0024] - Figure 2 shows a view from below of a portion of a floor according to embodiments of the present disclosure on the left and a cross-sectional view of a floor according to embodiments of the present disclosure on the right;

[0025] - Figure 3 shows a press roller that can be used to obtain a support layer of the described floor;

[0026] - Figure 4 shows the construction of a FEM model of a Berlin Artificial Athlete (AA) placed on a track and field runway, which is a device for measuring FR (EN 14808), on the left and an example of a floor used in the experimental tests described in the present application on the right;

[0027] - Figure 5 presents the results of FEM simulations highlighting the FR values due to different conditions of the voids in the bottom layer of the floor;

[0028] - Figure 6 presents the results of FEM simulations highlighting the FR values due to variations in the cavity depth values;

[0029] - Figure 7 presents the FR values due to different cavity volumes, given the same total thickness of the floor;

[0030] - Figure 8 presents a comparison between the FR results obtained by floors comprising cavities of different shapes;

[0031] - Figure 9 presents a comparison of the results of FR obtained from floors comprising cavities of different shapes, given the same floor thickness and cavity depth. DETAILED DESCRIPTION

[0032] In the following description, various specific details are shown in order to provide a thorough understanding of examples intended to enable practitioners to practice the described implementations. Implementations can be obtained without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the implementations.

[0033] Reference to "an embodiment" or "one embodiment" in the framework of this description is intended to indicate that a particular configuration, construction, or feature described in relation to the embodiment is included in at least one embodiment. Thus, use of formal language such as "in an embodiment," or "in one embodiment" appearing in various places in this description are not necessarily all referring to one and the same embodiment. Furthermore, a particular configuration, construction, or feature can be combined in any appropriate way in one or more embodiments.

[0034] The references used herein are provided for convenience only and thus do not limit the scope of protection or the embodiments.

[0035] Figure 1 Perspective view of a portion of a floor 1 comprising a tread layer 2 (which, when the floor 1 is laid in place, faces upwards), which in turn comprises a layer of elastomeric material; and a support layer 3 (which, when the floor 1 is laid in place, faces downwards), which in turn also comprises a layer of elastomeric material.

[0036] The two layers 2 and 3 can be joined together - typically during operations leading to the formation of the floor 1 - in a joining plane 4, which (in Figure 2 is visible on the right in Fig. 1) defines the interface surface between the two layers 2 and 3.

[0037] The tread layer can comprise an inner portion 2a with a continuous structure, which is joined to the support layer 3 in a position corresponding to the joining plane 4; and an outer portion, opposite the support layer 3, which presents a surface pattern exhibited by the presence of protrusions 6 extending between a root plane B (corresponding to the interface with the inner portion 2a) and a top plane T. In one embodiment, the height of the protrusions in the protrusions 6, i.e. the distance between the root plane B and the top plane T (which is designated by S2 on the right in Figure 2 Fig. 1), is equal to at least 30% and preferably about 33% of the thickness S1 of the tread layer 2, which, as already mentioned, is measured between the joining plane 4 and the top plane T of the protrusions 6.

[0038] The support layer 3 has, on the side opposite the tread layer 2 (thus on the side facing the subfloor on which the floor 1 is laid), a series of cavities distributed in the layer of elastomeric material. The cavities and protrusions can be formed by providing, on the calender rolls, a pattern corresponding and complementary to the desired cavities and protrusions.

[0039] The cavity is open on the side opposite to the tread layer. The cavity is open precisely on the underside of the floorboard 1 so as to be bounded (i.e., surrounded) by ribs 8 having a uniform height and extending so as to constitute a regular rib network for supporting the floorboard 1.

[0040] In particular, the floor panel 1 comprises a supporting layer 3 comprising a layer of elastomeric material having a first arrangement of cavities with an oval cross section 5 .

[0041] from Figure 2 As can be seen in the view from below (on the left), the support layer 3 comprises a first arrangement of cavities with an elliptical cross section 5 having a major axis A (main dimension, ie length) and a minor axis B (minor dimension, ie width).

[0042] exist Figure 2 In the example shown in FIG. 1 (on the upper left), the major axis A is oriented along the length direction Z of the floor (ie, the running direction).

[0043] In one or more embodiments, the cavities 5 of the first arrangement of cavities may present a major axis A oriented in a direction transverse to the direction of elongation Z of the floor.

[0044] As already explained in the introductory part of this description, Figure 1 and Figure 2 The above-mentioned direction designated by the double-headed arrow Z in the figure can be identified in a certain and unique way, because the flooring to which reference is made is usually produced in the form of sheets wound into rolls. The sports flooring forming the subject of the present disclosure can be presented in the form of sheets wound into rolls longitudinally. A plurality of sheets are wound into rolls and unrolled longitudinally (i.e. in the direction of elongation) one after another, wherein the longitudinal direction of each sheet extends exactly in the direction of running. The Z direction also generally corresponds to the direction in which the calendering operation is performed. Therefore, the sports flooring may comprise a plurality of floor sheets having a longitudinal dimension, which are longitudinally aligned in a manner such that each of the plurality of floor sheets is longitudinally aligned with each of the other floor sheets of the plurality of floor sheets.

[0045] In one or more embodiments, each cavity 5 of the first arrangement of cavities may further extend along tapered walls (or walls tapering in the direction of the treading layer 2) within the thickness of the supporting layer 3. Such characteristics may be a result of minimal deformation of the walls following the step of removal from the mold.

[0046] In one or more embodiments, the support layer 3 may also include a second arrangement of cavities distributed in the elastomeric material layer having an elliptical cross-section 5a, the elliptical cross-section having a first axis a and a second axis b, the first axis a and the second axis b being orthogonal and coplanar with the major axis A of the elliptical cross-section of the cavity 5 in the first arrangement of cavities.

[0047] In one or more embodiments, the first axis a and the second axis b may have the same extension.

[0048] In one or more embodiments, the cavity 5a of the second arrangement of cavities has an elliptical cross-section, wherein the first axis a and the second axis b have a smaller extension than the major axis A of the cross-section of the cavity 5 of the first arrangement of cavities.

[0049] In one or more embodiments, the first axis a and the second axis b of the cavity 5a of the second arrangement of cavities have a smaller extension than the minor axis B of the cross section of the cavity 5 of the first arrangement of cavities.

[0050] In one or more embodiments, each cavity 5a of the second arrangement of cavities may further extend along tapered walls (or walls that taper in the direction of the treading layer 2) within the thickness of the supporting layer 3. Such characteristics may be the result of minimal deformation of the walls following the step of removal from the mold.

[0051] The cavity 5 of the first arrangement of cavities may present an elliptical cross section with a major axis A comprised between 6 and 18 mm, preferably between 9 and 15 mm, more preferably between 11 and 15 mm.

[0052] In one or more embodiments, the cavity 5 of the first arrangement of cavities may present an elliptical cross-section with a minor axis B comprised between 6 and 12 mm, preferably between 6 and 10 mm, more preferably between 7 and 10 mm.

[0053] Preferably, the ratio between the extension of the major axis A and the extension of the minor axis B is comprised between 1 and 3, preferably between 1 and 2.

[0054] In one or more embodiments, the cavity 5a of the second arrangement of cavities may present an elliptical cross-section with a first axis a comprised between 0 and 8 mm, preferably between 2 and 6 mm, more preferably between 3 and 5 mm.

[0055] The cavity 5a of the second arrangement of cavities may present an elliptical cross section with a second axis b comprised between 0 and 8 mm, preferably between 2 and 6 mm, more preferably between 3 and 5 mm.

[0056] Preferably, the ratio between the extension of the first axis a and the extension of the second axis b is comprised between 1 and 2, preferably between 1 and 1.2.

[0057] In one or more embodiments, the distance C between the centers of two consecutive cavities of the first arrangement of cavities 5 can comprise between 12 mm and 32 mm, preferably between 12 mm and 27 mm, more preferably between 14 mm and 26 mm, said distance C being oriented along the length direction Z of the runway.

[0058] In one or more embodiments, the distance D between the centers of two consecutive cavities of the first arrangement of cavities 5 can comprise between 12 mm and 32 mm, preferably between 15 mm and 24 mm, more preferably between 17 mm and 21 mm, said distance D being oriented in a direction transverse to the length direction Z of the floor 1.

[0059] The depth of the first arrangement of cavities 5 and of the second arrangement of cavities 5a extending within the thickness of the support layer 3 can be the same or different from each other. In one or more embodiments, the depth of the cavities 5 can comprise between 2 mm and 15 mm, preferably between 3 mm and 10 mm, more preferably between 3 mm and 6 mm.

[0060] In one or more embodiments, the depth of the cavities 5a can comprise between 2 mm and 15 mm, preferably between 3 mm and 10 mm, more preferably between 3 mm and 6 mm.

[0061] The product of the distance C and of the distance D (horizontal and vertical distances between the centers of two consecutive main ellipses, respectively) identifies a section of the surface that repeats in a regular manner on the surface and contains two main ellipses and two secondary ellipses. This area is defined as a "unit element of the moving surface".

[0062] The unit element described above can have an area comprised between 144 mm 2 and 1024 mm 2 , preferably between 180 mm 2 and 648 mm 2 , more preferably between 238 mm 2 and 546 mm 2 .

[0063] A floor having a surface area of 1 m 2 that forms the subject of the present disclosure can thus comprise between 976 and 6944 unit elements, preferably between 1543 and 5555, more preferably between 1831 and 4201.

[0064] The floor forming the subject of the present disclosure can comprise a first arrangement of cavities 5 with an elliptical cross-section, wherein the number of cavities per square meter of floor comprises between 1952 cavities and 13888 cavities, preferably between 3086 cavities and 11110 cavities, more preferably between 3662 cavities and 8402 cavities.

[0065] The floor forming the subject of the present disclosure can further comprise a second arrangement of cavities 5a with an elliptical cross-section having a first axis a and a second axis b orthogonal to each other and coplanar with the major axis A, wherein the number of cavities per square meter of floor comprises between 1952 cavities and 13888 cavities, preferably between 3086 cavities and 11110 cavities, more preferably between 3662 cavities and 8402 cavities.

[0066] In one or more embodiments, the cavities 5; 5a of the floor can occupy a volume equal to at least 12% of the volume of the support layer.

[0067] The support layer 3 can have a thickness comprised between 3 mm and 15 mm, preferably between 6.5 mm and 10 mm. The tread layer 2 can have a thickness comprised between 3 mm and 9 mm, preferably between 4 mm and 8 mm, more preferably between 5 mm and 7.5 mm.

[0068] The total thickness of the floor can be comprised between 6 mm and 18 mm, preferably between 10.5 mm and 16 mm, still more preferably between 13.5 mm and 15 mm.

[0069] The geometry of the cavities with an elliptical cross-section generates a network of ribs that is uniform and homogeneous, wherein the unit element is constantly repeated. The ribs as a whole act as a support formation of the floor, and / or protrude substantially to the same extent in the direction normal to the tread layer.

[0070] Composition of the tread layer and the support layer

[0071] The tread layer 2 and the support layer 3 both comprise at least one layer of elastomeric material. The expression "at least one layer of elastomeric material" means at least one layer comprising at least one elastomer.

[0072] Composition of the tread layer

[0073] The tread layer 2 comprises at least one layer of elastomeric material. This layer can further comprise rubber powder, and preferably at least one filler, preferably a mineral filler. This layer can further comprise at least one pigment.

[0074] In one or more embodiments, the at least one elastomer can be selected in the group consisting of synthetic rubbers such as styrene-butadiene rubber (SBR), ethylene-propylene-diene- monomer (EPDM) rubber, natural rubber (NR) and mixtures thereof.

[0075] In one or more embodiments, the tread layer can comprise polyurethane as elastomer, preferably in combination with rubber powder. Polyurethanes that can be used can be obtained, for example, by reaction between a polyol and an isocyanate.

[0076] In one or more embodiments, mixtures based on NR, SBR and EPDM can be preferred in order to obtain a composition provided with good resistance to aging and deterioration by atmospheric agents, together with a pleasant aesthetic appearance and a good combination of maximum tensile strength and relative elongation at break.

[0077] In one or more embodiments, the at least one elastomer can be contained in the support layer in an amount comprised between 7 and 50 wt% (% w / w) of the layer, preferably comprised between 20 and 35 wt%.

[0078] In one or more embodiments, the at least one elastomer can comprise: styrene-butadiene rubber (SBR) in an amount comprised between 5 and 30 wt% of the layer; EPDM rubber in an amount equal to or higher than 5 wt%, preferably between 6 and 15 wt% of the layer; EPDM rubber and / or natural rubber (NR) in an amount equal to or higher than 5 wt%, preferably between 6 and 15 wt% of the layer.

[0079] In one or more embodiments, the at least one filler contained in the composition can be selected in the group consisting of fillers of organic nature (wood flour, cellulose fibers) or of inorganic nature (mainly talc, calcium carbonate, silica, carbon black, kaolin, aluminum trioxide, magnesium dioxide), possibly of biological origin. The at least one filler is present in an amount comprised between 30 and 200 wt%, preferably comprised between 30 and 150 wt% with respect to the weight of the at least one elastomer.

[0080] In one or more embodiments, the rubber powder (preferably obtained from a cross-linked elastomer mixture by mechanical treatment) is selected from rubber production processes, either pre-consumption or post-consumption. The rubber powder is preferably free of halogens and can have a particle size comprised between 50 pm and 2 mm, preferably comprised between 400 pm and 1 mm. The rubber powder can be in an amount comprised between 30 and 200 wt%, preferably comprised between 100 and 150 wt% with respect to the weight of the at least one elastomer.

[0081] In one or more embodiments, the tread layer can comprise at least one pigment of inorganic nature (wherein, for example, red iron oxide, yellow iron oxide, brown iron oxide, chromium oxide green and titanium dioxide) or organic pigments (wherein, by way of example only, pigments of the monoazo, diazo, phthalocyanine family and quinacridone, perylene and perinone and diketopyrrolopyrrole family). The pigments can be present in an amount comprised between 0.3 and 25% by weight, preferably comprised between 1 and 20% by weight, with respect to the weight of the support layer.

[0082] In one or more embodiments, the composition of the tread layer can also comprise at least one compatibilizing agent in combination with at least one reinforcing filler, so as to obtain a tread layer capable of imparting resistance to impact, wear and tearing to the surface on which it is to be applied.

[0083] In one or more embodiments, the at least one compatibilizing agent can be selected in the group consisting of silanes (preferably mercaptosilanes and / or vinylsilanes), hydrocarbon-derived resins and / or waxes (for example, resins known as benzofuran resins, coumarone resins, aliphatic hydrocarbon resins (commonly known as C5 resins, C9 resins or C5 / C9 resins), long-chain fatty acids (preferably stearic acid and oleic acid) and mixtures thereof.

[0084] In one or more embodiments, the at least one compatibilizing agent can consist of a mixture of mercaptosilanes, stearic acid and coumarone.

[0085] The mixture of the above presents the double advantage of facilitating the addition of the filler and reducing the viscosity of the composition, thus facilitating the handling of the composition, for example by calendering.

[0086] In one or more embodiments, the silanes can be used in liquid form. Mercaptosilanes can be preferably used when the support layer production process envisages a step of sulfur cross-linking of the mixture, while vinylsilanes can be preferably used when the cross-linking phase is performed using peroxides.

[0087] In one or more embodiments, the composition of the tread layer can comprise mercaptosilanes and / or vinylsilanes in an amount comprised between 0.1 and 2% by weight, preferably comprised between 0.3 and 1% by weight, of the composition.

[0088] In one or more embodiments, the composition of the tread layer can comprise coumarone in an amount comprised between 1 and 3% by weight, preferably comprised between 1.5 and 2.5% by weight, of the composition.

[0089] In one or more embodiments, the composition of the tread layer can comprise long-chain fatty acids, preferably stearic acid, in an amount comprised between 0.3 and 2% by weight, preferably comprised between 0.5 and 1% by weight, of the composition.

[0090] In one or more embodiments, the composition of the tread layer can comprise chemical additives, also known as processing aids, which are used to control the viscosity and processability of the composition in the industrial equipment.

[0091] In one or more embodiments, the processing aid can for example be a plasticizing compound which enables to adjust the viscosity of the composition and to vary the glass transition temperature of the elastomer with the crosslinking process of the composition. The plasticizing compound can be selected in the group consisting of phthalates, phosphates, adipates, sebacates, aliphatic and aromatic oils, antiozonants and dispersing waxes, polyethylene glycol (PEG), fatty acid esters, metal soaps such as calcium stearate and zinc stearate, zinc oxide and hard fat, reinforcing resins, adhesion promoters or inhibitors.

[0092] The crosslinking phase to obtain the composition of the tread layer can be performed by vulcanization using sulfur process and accelerators, or with sulfur donors, or with peroxide crosslinking agents such as dicumyl peroxide or tert-butyl peroxide, or with a combination of the three mentioned processes.

[0093] In one or more embodiments, the crosslinking accelerator can for example be selected in the group consisting of CBS (cyclohexylbenzothiazyl sulfenamide, CAS number 95-33-0), TMTD (tetramethylthiuram disulfide, CAS number 137-26-8) or MTB (mercaptobenzothiazole, CAS number 149-30-4), ZDBC (zinc dibutyl dithio-carbamate, CAS number 136-23-2), or other accelerators of the same family (sulfenamides, thiurams, thiazoles, carbamates).

[0094] Composition of the support layer

[0095] In one or more embodiments, the support layer 3 comprises at least one layer of elastomeric material comprising at least one elastomer. The layer of elastomeric material can comprise at least one elastomer, a rubber powder, and preferably at least one filler, preferably a mineral filler.

[0096] In one or more embodiments, the at least one elastomer can be selected in the group consisting of synthetic rubbers such as styrene-butadiene rubber (SBR), ethylene-propylene-diene- monomer (EPDM) rubber, natural rubber (NR) and mixtures thereof.

[0097] In one or more embodiments, the at least one elastomer can be comprised in the composition of the support layer in an amount comprised between 7 wt% and 50 wt%, preferably comprised between 20 wt% and 35 wt%.

[0098] In one or more embodiments, the at least one elastomer can comprise: styrene-butadiene rubber (SBR) in an amount comprised between 5 wt% and 25 wt% of the composition, natural rubber (NR) preferably in an amount comprised between 0 wt% and 10 wt% of the composition, and EPDM rubber preferably in an amount comprised between 0 wt% and 10 wt% of the composition of the support layer.

[0099] In one or more embodiments, the at least one filler comprised in the composition can be chosen in the set consisting of fillers of organic nature (wood flour, cellulose fibers) or of inorganic nature (mainly talc, calcium carbonate, silica, carbon black, kaolin, aluminum trioxide, magnesium dioxide), possibly of biological origin. The at least one filler is present in the composition in an amount comprised between 30 wt% and 200 wt%, preferably comprised between 30 wt% and 100 wt%, relative to the weight of the at least one elastomer.

[0100] In one or more embodiments, the rubber powder is chosen from halogen-free rubber production processes, either pre-consumer or post-consumer, with a particle size from 50 pm to 4 mm (preferably between 400 pm and 2 mm), or from waste tire (ELT) recycling processes, shredded or devulcanized, and is present in the composition in an amount comprised between 30 wt% and 200 wt%, preferably comprised between 130 wt% and 180 wt%, relative to the weight of the at least one elastomer.

[0101] In one or more embodiments, the described composition comprises at least one pigment of inorganic or organic nature, for example chosen from the materials already indicated for the tread layer. The pigment is present in the composition in an amount comprised between 0.3 wt% and 10 wt%, preferably comprised between 0.5 wt% and 7 wt%, relative to the weight of the formulation.

[0102] In one or more embodiments, at least one compatibilizing agent is present. In one or more embodiments, the at least one compatibilizing agent can be chosen in the set consisting of silanes (preferably mercaptosilanes and / or vinylsilanes), resins of hydrocarbon origin and / or waxes (for example, resins known as benzofuran resins, coumarone resins, aliphatic hydrocarbon resins (generally known as C5 resins, C9 resins or C5 / C9 resins), long-chain fatty acids (preferably stearic acid and oleic acid) and mixtures thereof.

[0103] In one or more embodiments, the composition of the support layer comprises coumarone in an amount comprised between 1 wt% and 3 wt%, preferably comprised between 1.5 wt% and 2.5 wt%, of the composition.

[0104] In one or more embodiments, the composition of the support layer can comprise long chain fatty acids in an amount comprised between 0.3 wt% and 2 wt%, preferably comprised between 1 wt% and 2 wt% of the composition, preferably stearic acid.

[0105] In one or more embodiments, the composition of the support layer can comprise chemical additives, also known as processing aids, used to control the viscosity and processability of the composition in industrial equipment.

[0106] In one or more embodiments, the processing aids can for example be plasticizing compounds which enable to adjust the viscosity of the composition and to vary the glass transition temperature of the elastomer with the crosslinking process of the composition. The plasticizing compounds can be selected in the set consisting of phthalates, phosphates, adipates, sebacates, aliphatic and aromatic oils, antiozonants and dispersing waxes, polyethylene glycol (PEG), fatty acid esters, metal soaps such as calcium stearate and zinc stearate, zinc oxide and hard fat, reinforcing resins, adhesion promoters or inhibitors.

[0107] The crosslinking phase to obtain the composition of the two layers can be performed by vulcanization using sulfur process and accelerators, or with sulfur donors, or with peroxide crosslinking agents (for example dicumyl peroxide or tertiary butyl peroxide), or with a combination of the three processes mentioned.

[0108] In one or more embodiments, the crosslinking accelerators can for example be selected in the set consisting of CBS (cyclohexyl benzothiazole sulfenamide, CAS number 95-33-0), TMTD (tetramethylthiuram disulfide, CAS number 137-26-8) or MTB (mercaptobenzothiazole, CAS number 149-30-4), ZDBC (zinc dibutyl dithio carbamate, CAS number 136-23-2), or other accelerators of the same family (sulfenamides, thiurams, thiazoles, carbamates).

[0109] The compositions for the production of the support layer and of the tread can be obtained with a mixer, in which at least one elastomer and rubber powder, and optionally at least one plasticizer, at least one filler, optionally at least one reinforcing filler, chemical additives and crosslinking additives are first added in one pass process or in a succession of passes.

[0110] In one or more embodiments, the obtained composition can be processed and transformed into layers of for example coated floors, for example using a process of molding, extrusion or calendering.

[0111] In one or more embodiments, the composition thus processed can be crosslinked via a thermal process such as hot calendering or hot molding, or via an irradiation process using a microwave source, infrared radiation or electron beam, or via hot air crosslinking.

[0112] The obtained floor can present a slipperiness according to EN 13036-4 from 80 to 110 (dry) or higher or equal to (>) 47 (wet). It can present a shock absorption according to EN 14808 between 25% and 50%, preferably between 35% and 50%. It can present a vertical deformation comprised between 0.6 mm and 3 mm, preferably comprised between 1 mm and 2.5 mm. It can present an abrasion value according to UNI EN ISO 5470-1 (H18 wheels, 1 kg / wheel, 1000 cycles) lower or equal to (≤) 4000 mg, preferably ≤ 3000 mg. The floor can present a maximum tensile strength according to EN 12230 ≥ 0.5 MPa (preferably ≥ 0.6 MPa). It can present a relative elongation at break according to EN 12230 ≥ 100%, preferably ≥ 120%. The floor can present a hardness (Shore A hardness; UNI ISO 48-4) of 45-65 Shore A, preferably 50-63 Shore A.

[0113] Examples

[0114] In the following content a non-limiting example of floor according to an embodiment of the present disclosure is provided.

[0115] The floor comprises a tread layer having a thickness equal to 5 mm, obtained with a mixture of NR / SBR / EPDM elastomers in an amount comprised between 25 and 35 wt%, a mixture of mineral fillers (calcium carbonate, kaolin, silica) in an amount comprised between 30 and 100 wt% by weight of the elastomers, rubber powder in an amount comprised between 100 and 150 wt% by weight of the elastomers, iron oxide pigments in an amount equal to 10 wt% of the layer. The layer is vulcanized by means of a sulfur cross-linking process in the presence of zinc oxide and CBS accelerators.

[0116] The floor further comprises a support layer, obtained with a mixture of NR / SBR / EPDM elastomers in an amount comprised between 20 and 35 wt%, a mixture of mineral fillers (calcium carbonate, kaolin, silica) in an amount comprised between 30 and 100 wt% by weight of the elastomers, and rubber powder in an amount comprised between 130 and 180 wt% by weight of the elastomers. The layer is vulcanized by means of a sulfur cross-linking process in the presence of zinc oxide and CBS accelerators.

[0117] The support layer having a thickness of 9 mm comprises: a first arrangement of cavities with an elliptical section having a major axis A of 14 mm and a minor axis B of 9 mm; and a second arrangement of cavities with an elliptical section having a first axis a of 6 mm and a second axis b of 5 mm. The cavities have a depth of 6.5 mm.

[0118] Figure 3 An example of a press cylinder used to obtain the cavities of the support layer of the described floor is shown.

[0119] Properties of the floor

[0120] Table 1 presents the properties of the floor obtained with the parameters according to the example compared to a floor obtained with the same formulation but having hexagonal cavities.

[0121] Table 1

[0122]

[0123] It is noted that the 13% increase in tensile strength at break corresponding to a 3% increase in mass per unit area, and also a simultaneous 7% increase in relative elongation at break. At the same time, a significant 37% increase in tear strength is highlighted. Surprisingly, a significant 3% increase in the FR value also corresponds to an increase in mass per unit area.

[0124] Verification of properties of the floor

[0125] As shown in the Figure 4 detailed FEM model of the materials constituting the product and using the FR measurement equipment, the properties of the described floor were examined more deeply, where on the left the construction of the FEM model of a Berlin artificial athlete (AA) placed on a track is schematically represented and on the right an example of the floor used in the tests described below is schematically represented, which is the FR measurement equipment (EN 14808).

[0126] The FEM model was applied to evaluate the FR value of a visco-hyperelastic material using various specific formulations, to identify the material that presents higher performance in the space of the geometric shape parameters that exhibit possible solutions industrially applicable to a track. The model validated by generating some of the most interesting solutions, for which the mechanical properties were measured.

[0127] In particular, the research carried out confirms that, using specific formulations of the floor layer, combined with specific geometric characteristics of the cavities of the support layer, even in the presence of small dimensional variations of the cavities, it is possible to obtain the optimal elastic response of the floor and the accurate selection of the specific size of the void fraction and the cavity shape in the support layer guarantees the achievement of high FR values associated with excellent mechanical properties.

[0128] Figure 5 The results of simulations carried out to evaluate the influence of the volume of cavities with different geometries on the FR value of floors with the same total thickness are presented. These simulations make it possible to verify, in a completely unexpected way, that, in addition to the known ratio between FR value and cavity volume, there are geometric solutions where, given the same void volume, the difference in FR is very significant, even in the region of 3-5%.

[0129] Furthermore, additional simulations were performed to understand the influence of the cavity depth, and in particular to understand whether this parameter is prevalent compared to other geometrical aspects: also in this case, the conclusions are surprising, since even if the proportionality between cavity depth and FR values ​​is confirmed, as Figure 6 As shown in Figure 2 , the cavity depth does not dominate over other variations in geometry. In practice, it is true that higher FR values ​​generally correspond to larger cavity depths, and it is also true that within the framework of the same depth value, it is possible to identify solutions with different geometries that can achieve significantly higher variations in FR.

[0130] According to further in-depth analysis, Figure 7 As shown in Figure 2, a series of experiments were performed to simulate cavity geometries with elliptical cross-sections to verify the effect of geometric variations on FR values. This series of experiments yielded interesting and unexpected results compared to similar results obtained on cavities with hexagonal bases. The experiments on cavity geometries with elliptical cross-sections confirmed the trend pattern of the results for the hexagonal shape, but highlighted a much narrower distribution of results (i.e., reduced scatter), while maintaining the possibility of selecting different FR values ​​given the same void volume.

[0131] By superimposing the results, such as Figure 8 As shown in , it is possible to confirm another surprising and unexpected aspect, namely that, given the same void volume, cavities with an elliptical shape are generally able to achieve higher FR values ​​than cavities with a hexagonal shape.

[0132] Additional in-depth studies were then conducted to verify the effect of variations in the two geometrical parameters (width and height) of the ellipse and the hexagon, while keeping the depth of the cavity and the thickness of the floor constant. The results obtained were particularly unexpected and surprising. Figure 9As can be seen, for the hexagonal cavity, small dimensional variations significantly affect the FR value; alternatively, for the cavity with elliptical section, no such thing was found, which instead presents a significant regularity on the variation of the FR value when the dimensions of the cavity vary. It was also confirmed that, given the same geometric conditions, the FR value of the floor with the cavity with elliptical section is higher than that of the floor with the cavity with hexagonal section.

[0133] From an application point of view, the above results have particularly important consequences: in the production of technical articles made of rubber, there are production tolerances which can lead to the acceptance of articles which, although appearing similar to each other, can present differences in the FR value in actual use, which until now were difficult to explain. Also, the steps of installation of these materials require the use of glue, which can possibly fill part of the cavities and thus alter the FR value of the material in a sometimes unpredictable way.

[0134] The cavity with elliptical section, combined with the use of the elastomeric mixture for the simulation of the application, guarantees the possibility of selecting the FR value and thus the mechanical properties of the floor particularly suitable (for example good resistance to spikes for track shoes) in a way which is partly independent of the void fraction (i.e. the volume of the cavities).

[0135] The present application makes it possible to obtain a floor with constant FR value and particularly consistent behaviour regardless of the production or installation conditions, and thus defines a new generation of sports surfaces which are highly efficient and superior to previous sports surfaces.

[0136] In particular, the floor as described in the present application presents the following advantages:

[0137] √ High consistency of the elastic response (best constancy of the FR value, despite the variations in the dimensions and shape of the lattice of the supporting layer which can be caused by variations in the production and installation conditions);

[0138] √ High FR value, even when lower than the void fraction values of existing solutions, or in other words, higher FR value given the same void fraction;

[0139] √ Significant freedom in the choice of the mechanical properties of the finished product: once the FR value is chosen, it is possible to choose a combination by selecting the geometric parameters of the surface which will make it possible to obtain the best mechanical properties of the surface for different use situations (for training, for competition, use with shoes with different spikes).

Claims

1. Sports floor (1) comprising: - a tread layer (2) comprising at least one layer of elastomeric material; and - a support layer (3) comprising at least one layer of elastomeric material, wherein the support layer (3) comprises a first arrangement of cavities with an elliptical cross-section (5).

2. Sports floor (1) according to claim 1, wherein The support layer (3) comprises a first arrangement of cavities with an elliptical cross-section (5) having a major axis (A) oriented along the elongation direction (Z) of the floor.

3. Sports floor (1) according to claim 1 or claim 2, wherein The support layer (3) comprises a second arrangement of cavities with an elliptical cross-section (5a) having a first axis (a) and a second axis (b) which are orthogonal and coplanar with the major axis (A) of the elliptical cross-section of the cavities in the first arrangement of cavities (5).

4. Sports floor (1) according to claim 3, wherein The first axis (a) and the second axis (b) have the same extension.

5. Sports floor (1) according to claim 3 or claim 4, wherein The first axis (a) and the second axis (b) have a smaller extension than the major axis (A) of the elliptical cross-section of the cavities (5) in the first arrangement of cavities.

6. Sports floor (1) according to any of the preceding claims, wherein Each cavity (5a) has an elliptical cross-section wherein the ratio between the extension of the first axis (a) and the extension of the second axis (b) is comprised between 1 and 2, preferably between 1 and 1.

2.

7. Sports floor (1) according to any of the preceding claims, wherein The support layer (3) comprises a first arrangement of cavities with an elliptical cross-section (5) having a major axis (A) comprised between 6 mm and 18 mm, preferably between 9 mm and 15 mm, more preferably between 11 mm and 15 mm.

8. Sports floor (1) according to any of the preceding claims, wherein The support layer (3) comprises a first arrangement of cavities with an elliptical cross-section (5) having a minor axis (B) comprised between 6 mm and 12 mm, preferably between 6 mm and 10 mm, more preferably between 7 mm and 10 mm.

9. Sports floor (1) according to any of the preceding claims, wherein The support layer (3) comprises a second arrangement of cavities with an elliptical cross-section (5a) having a first axis (a) comprised between 0 and 8 mm, preferably between 2 mm and 6 mm, more preferably between 3 mm and 5 mm.

10. Sports floor (1) according to any of the preceding claims, wherein, The support layer (3) comprises a second arrangement of cavities with an elliptical cross-section (5a) having a second axis (b) comprised between 0 and 8 mm, preferably between 2 and 6 mm, more preferably between 3 mm and 5 mm.

11. Sports floor (1) according to any of the preceding claims, wherein The distance (C) between the centers of two consecutive cavities in the first arrangement of cavities (5) is comprised between 12 mm and 32 mm, preferably between 12 mm and 27 mm, more preferably between 14 mm and 26 mm, the distance (C) being oriented along the elongation direction (Z) of the track.

12. Sports floor (1) according to any of the preceding claims, wherein The distance (D) between the centers of two consecutive cavities in the first arrangement of cavities (5) is comprised between 12 mm and 32 mm, preferably between 15 mm and 24 mm, more preferably between 17 mm and 21 mm, the distance (D) being oriented in a direction transverse to the elongation direction (Z) of the floor (1).

13. Sports floor (1) according to any of the preceding claims, wherein Said support layer (3) has a thickness comprised between 3 mm and 15 mm, preferably comprised between 6.5 mm and 10 mm.

14. Sports floor (1) according to any of the preceding claims, wherein Said tread layer (2) has a thickness comprised between 3 mm and 9 mm, preferably comprised between 4 mm and 8 mm, more preferably comprised between 5 mm and 7.5 mm.

15. A track for athletics, in particular for running, provided with a floor (1) according to any one of claims 1 to 14.

Images