POLYMERIC FOAM MATERIAL FOR SHOCK PADS IN ARTIFICIAL GRASS SYSTEMS

Abstract

The present disclosure relates to a shock pad for artificial turf systems, wherein said shock pad comprises low density expanded polyethylene (EPE). An object of the present disclosure is to provide a shock pad providing improved shock absorption and/or energy restitution characteristics to artificial turf systems. Another object of the present disclosure is to provide artificial turf systems having improved shock absorption and/or energy restitution characteristics, especially over a prolonged period of time.

Claims

1. A shock pad for artificial turf systems, wherein said shock pad comprises low density expanded polyethylene particle foam (EPE).

2. The shock pad for artificial turf systems according to claim 1, wherein said low density of expanded polyethylene (EPE) ranges from 10-100 kg/m.sup.3.

3. The shock pad for artificial turf systems according to claim 2, wherein said low density of expanded polyethylene (EPE) ranges from 15-80 kg/m.sup.3.

4. The shock pad for artificial turf systems according to claim 1, wherein said low density expanded polyethylene EPE is made of a blend, on a polymer level, comprising 30-80% by weight of low density polyethylene and 20-70% by weight of high density polyethylene, based on the weight of low density expanded polyethylene EPE.

5. The shock pad for artificial turf systems according to claim 4, wherein said shock pad further comprises 0-30% by weight of one or more polyolefins, wherein the total sum of components amounts to 100%.

6. The shock pad for artificial turf systems according to claim 5, wherein said polyolefins is a mechanical mix of several particle foams comprising 5-95% by weight of a polypropylene particle foam and 95-5% by weight of a polyethylene particle foam, based on the total weight of said mix, whereby the sum of the individual quantities together amounts to 100%.

7. The shock pad for artificial turf systems according to claim 1, wherein said shockpad comprises of a mix of particle foams comprising at least one of EPP, EPS, EPE, ETPU, EPET, EPBAT, EPLA, EPCL, EPHBH, EPHA, EPLA/PBTA blends, EPVC and EPE/PS blend, said mix comprises 5-95% by weight of EPE and 95-5% by weight of a second type of particle foam chosen from said group of particle foams, the second type is different from EPE, whereby the sum of the individual quantities together amounts to 100%.

8. The shock pad for artificial turf systems according to claim 1, wherein said shock pad comprises of a mix of particle foams comprising at least one of EPP, EPS, EPE, ETPU, EPET, EPBAT, EPLA, EPCL, EPHBH, EPHA, EPLA/PBTA blends, EPVC and EPE/PS blend, comprising 5-95% by weight of EPE, 95-5% by weight of a second type of particle foam and 20-50% by weight of a third type of particle foam that is different from EPE and the second type, all types are chosen from said group of particle foams, whereby the sum of the individual quantities together amounts to 100%.

9. An artificial turf system comprising at least a shock pad according to claim 1.

10. A playground system comprising at least a shock pad according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following Figures are exemplary embodiments, which are provided to illustrate the present disclosure. The figures are illustrative of the examples, which are not intended to limit devices made in accordance with the disclosure to the materials, conditions, or process parameters set forth herein.

[0026] FIG. 1 shows the HIC value (y) according to EN117 as a function of drop height (x).

[0027] FIG. 2 shows a front view of components of 3G turf products.

DETAILED DESCRIPTION

[0028] The present disclosure thus relates to a shock pad for artificial turf systems, wherein said shock pad comprises low density expanded polyethylene particle foam (EPE).

[0029] One or more of the above discussed objects of the present disclosure is achieved by a shock pad comprising low density expanded polyethylene (EPE). Surprisingly, it has been found that such material provides improved shock absorption and/or energy restitution characteristics.

[0030] In an embodiment of the present disclosure the density of the expanded polyethylene (EPE) according to the present disclosure ranges from 10-100 kg/m.sup.3.

[0031] In another embodiment of the present disclosure the density of the expanded polyethylene (EPE) according to the present disclosure ranges from 15-80 kg/m.sup.3.

[0032] In an embodiment of the present disclosure the low density expanded polyethylene EPE is made of a blend, on a polymer level, comprising 30-80% by weight of low density polyethylene and 20-70% by weight of high density polyethylene, based on the weight of low density expanded polyethylene EPE. The total sum of components amounts to 100%.

[0033] In an embodiment of the present disclosure the blend further comprises 0-30% by weight of one or more polyolefins, especially polypropylene. The total sum of components amounts to 100%.

[0034] In an embodiment of the present disclosure the one or more polyolefins is a mechanical mix of several particle foams comprising 5-95% by weight of a polypropylene particle foam and 95-5% by weight of a polyethylene particle foam, based on the total weight of said mix, whereby the sum of the individual quantities together amounts to 100%.

[0035] In an embodiment of the present disclosure the shockpad comprises a mix of particle foams, wherein the mix can comprise at least one of EPP, EPS, EPE, ETPU, EPET, EPBAT, EPLA, EPCL, EPHBH, EPHA, EPLA/PBTA blends, EPVC and EPE-PS blend , said mix comprises 5-95% by weight of EPE and 95-5% by weight of a second type of particle foam chosen from said group of particle foams, whereby the sum of the individual quantities together amounts to 100%. In such an embodiment the shockpad comprises a mix of two particle foams, for example 70% by weight of EPE and 30% by weight of EPHA. It is clear that the second type of particle foam is different from EPE in such a mix of particle foams.

[0036] In an embodiment of the present disclosure the shockpad comprises a mix of particle foams, wherein the mix can comprise at least one of EPP, EPS, EPE, ETPU, EPET, EPBAT, EPLA, EPCL, EPHBH, EPHA, EPLA/PBTA blends, EPVC and EPE-PS blend, comprising 5-95% by weight of EPE, 95-5% by weight of a second type of particle foam and 20-50% by weight of a third type of particle foam, all types are chosen from said group of particle foams, whereby the sum of the individual quantities together amounts to 100%.%. It is clear that the second type of particle foam is different from both EPE and the third type of particle foam in such a mix of particle foams. It is also clear that the third type of particle foam is different from both EPE and the second type of particle foam in such a mix of particle foams. In such an embodiment the shockpad comprises a mix of three particle foams, for example 70% by weight of EPE, 20% by weight of EPET and 10% by weight of EPP.

[0037] The present disclosure furthermore relates to an artificial turf system, i.e. a multi-layered sports playing field, comprising at least a shock pad as discussed above. In such an artificial turf system a part of the substructure comprises at least a shock pad as discussed above.

[0038] The present disclosure furthermore relates to a playground system, i.e. a multi-layered playground system, comprising at least a shock pad as discussed above. In such a playground system a part of the substructure comprises at least a shock pad as discussed above.

[0039] The shock pad may be used as a shock pad under several kinds of playing fields, such as for example rugby pitches, tennis courts, hockey fields, indoor and outdoor playing fields, such as for example volleyball, handball, basketball, gymnastics, indoor and outdoor soccer pitches, children play grounds and running tracks.

[0040] The shock pad according to the present disclosure further provides a high capacity for drainage of liquid, for example (rain) water, from the artificial turf playing field due to its open three-dimensional structure. The drainage may include both vertical and horizontal drainage capabilities. The shockpad may also comprise one or more additional layers, such as a film, being pervious or impervious to liquid, a layer of fibrous material, such as a woven or a nonwoven, a two-dimensional grid or scrim, or a three-dimensional entangled mat of extruded filaments.

[0041] The present inventor made a comparison between commercially available shock pads material and the low density expanded polyethylene (EPE) according to the present disclosure. In Table 3 (see below) some parameters have been listed for both commercially available shock pads material and low density expanded polyethylene (EPE) according to the present disclosure. Reference materials shown in Table 3 are Expanded polypropylene particle foam (EPP), recycled ground crosslinked XPE and a possible expanded ETPU foam.

TABLE-US-00003 TABLE 3 Comparison between commercially available shock pads material and low density expanded polyethylene (EPE). E, Young's relative Modulus E Young's used for used for Modulus calculation, kg/m3 thickness, density material MPa MPa density m MPa /m3 Polypropylene, 1500-2000 1750  37.8 0.0234 66.15 EPP Pro Base 23 Polyethylene, 110-450 230 160 0.023 36.8 recycle PRO play 2 Schmitz TPU type 800 800 180 0.023 144 medium stiffness Polyethylene, 110-450 500 20 0.023 10 EPE target

[0042] Since recycled XPE cross linked foam and EPP particle foam are used as shock pad materials, the given density can be related to the Young's modulus of the base polymer used. A comparative relative E (Young's modulus) can be calculated, MPa/m.sup.3, corrected for the foam density.

[0043] ETPU foam could also be envisaged, and is available, but the foam density is higher than for EEP and also its relative price is higher, so although technically feasible, it would not become an economic viable alternative.

[0044] Hereinafter, the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that the disclosure can be embodied in various forms and thus is not limited to the embodiments described herein. In addition, in order to clearly describe the disclosure, parts irrelevant to the description of the disclosure are omitted in the drawings, and like reference numerals designate like parts throughout the specification.

[0045] Hereinafter, Examples of the present disclosure will be described in detail.

[0046] FIG. 1 shows the HIC value (y) according to EN117 as a function of drop height (x).

[0047] FIG. 2 shows a front view of components of 3G turf products.

[0048] Whilst 3G turf products 10 can vary in terms of their design and manufacture, they generally all share common components (see FIG. 2). The turf pile 1 itself is usually made from polyethylene (PE) with a primary backing material 4 of polypropylene (PP) that provides the structure and spacing that the pile 1 is woven into. A secondary backing 5 of a liquid polyurethane (PU) or latex is applied and allowed to set in order to bind the pile 1 to the backing 4. A stabilizing infill 3 is used to keep the PE fibres 1 vertical during use, and a performance infill 2 provides the correct level of impact resistance to reduce injuries and provide a similar feeling to natural grass. In some cases, there is also a shock pad 6 underneath which reduces the amount of performance infill 2. It is to be noted that such a turf product 10 is not restricted to the type of materials mentioned above. In some embodiments of a turf product additional layers beneath the shock pad, or additional layers between the secondary backing 5 and shock pad 6 are present. However, the present disclosure is not restricted to the specific construction and materials shown in FIG. 2. Shock pads are 10-50 mm thick, often 22 mm is used, but for particle foam also much thicker up to 50 mm can be used.

[0049] The following examples are provided to illustrate the present disclosure. The examples are merely illustrative and are not intended to limit devices made in accordance with the disclosure to the materials, conditions, or process parameters set forth therein.

EXAMPLE

[0050] A one step expanded PE based particle foam was obtained using a blend of 70% LDPE and 30% HDPE in a single screw extrude equipped with a 2nd stage melt cooling to which 7-10% CO.sub.2 was added and extruded through a die face cutter, producing an expanded foam with a density of 12-15 gr/l. The following materials were used. LDPE being ExxonMobil™ LDPE LD 100. BW with an MFI of 2 g/10 measured according to ISO 1133 at 2.16 kg/190° C. and HDPE Relene type 1020FA20 with an MFI of 2 g/10 min from Reliance Industries Mumbai, India, measured according to ISO 1133 at 2.16 kg 190° C. The 15 gr/1 foam had to be moulded using a compression step during moulding towards 20 gr/l. With steam pressure of 3-4 bars and a pre-impregnated air pressure, a sheet with a thickness of 2 cm and a density of 20 gr/l was thus obtained and compared to existing materials.

[0051] Testing points; point elastic vs volume elastic

[0052] Two factors are important. The relative Young's modulus gives an information about a point elastic property, important for ball bounce. In relation to preventing personal injury, a volume elastic property like the HIC value is used as a predictive parameter. The HIC test device is used worldwide in laboratories, by manufacturers and experts for the testing of protection mats or other damping materials (e.g. on playgrounds) The Head Injury Criterion (HIC) as measured according standard EN 1177 is a measure of the likelihood of head injury arising from an impact. The HIC can be used to assess safety related to vehicles, personal protective gear, and sport equipment. As each impact may damage the plate a new area of the plate shall be impacted for each drop. Tests shall be made at a range of drop heights starting at 300 mm and increasing in 300 mm increments until the HIC value exceeds 1500 or a height of 2000 mm is achieved, whichever occurs sooner.

[0053] Crosslinked XPE sheet is not used as it has a too high shock force reduction/elasticity. The ball will not bounce back properly. The new EPE foam with the low density appears to be more volume elastic than EPP and more elastic than the recycled crosslinked higher-density PE foam. FIG. 1 shows the HIC value (y) according to EN117 as a function of drop height (x). In FIG. 1 the “A” refers to polypropylene, EPP Pro Base 23, “B” to polyethylene, recycle Pro play 20 Schmitz and “C” to polyethylene, EPE according to the present disclosure.

[0054] The point elastic properties can be quantified using the EN15330-1 standard as referred to in the ESTO performance guide (European Synthetic Turf Organization). Several commercial materials were tested and compared to the obtained sheet of the EPE particle foam product according to the present disclosure and shown in Table 4.

TABLE-US-00004 TABLE 4 Comparison between commercial materials and EPE particle foam product according to the present disclosure. Conformity to EN 15330-1 Test conditions: ESTO Performance Guide for Shockpads except for test with load spreading plate results Shock sheet force density tickness, impression reduction pass/ shockpad material kg/m3 mm mm FR % fail Polypropylene, EPP 38 23 8.8 69.1 pass Pro Base 23 Polyethylene, recycle 150 20 5 60.6 pass PRO play 20 Schmitz EPE particle foam, 25 20 10 65 pass present invention 50/50 blend of 39 23 9.4 67 pass EPP Eperan M45 particle foam and EPE particle foam present invention XPE sheet Sekisui 300 10 6.8 80.5 nr XPE sheet Sekisui 250 12 7.4 84 nr XPE sheet Sekisui 416 12 8 71.7 nr XPE sheet Sekisui 357 14 8.5 48.5 nr nr not relevant

[0055] The results shown in Table 4 clearly indicate that the impression value of the EPE low density particle foam sheet according to the present disclosure is positioned between that of EPP particle foam and recycled crosslinked XPE. This means that with much reduced density, properties are surprisingly positioned between the existing and most used materials.

[0056] Without being bound to any theory, it is believed that the compressed and glued mix of crosslinked XPE waste is less of a homogenous material as the uniformly moulded EPE particle foam according to the present disclosure. Moreover, the cell wall forms a rigid honeycomb structure, which may give the foam another behaviour than non-cross linked foams. The intrinsic deformation of the polymer chain is altered by crosslinking with is not the case with a not cross-linked foam of the present disclosure.

[0057] Moreover, with the present disclosure it is now possible to prepare a deliberate mix of pre-expanded particle foams and to mould a shock pad from these materials. Table 4 also shows an example of a shock pad material that is made with 50% (m/m) Kaneka Eperan type M45 18 gr/l together with 50% (m/m) of EPE at 20 gr/l of the present disclosure. This mix of EPE and EPP particle foam shock pad was compression moulded to a density of 25 gr/, allowing to demonstrate that it is possible to produce a controlled blend of properties of the individual materials.

[0058] The compositions, methods, and articles can alternatively comprise, consist of, or consist essentially of, any appropriate materials, steps, or components herein disclosed. The compositions, methods, and articles can additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any materials (or species), steps, or components, that are otherwise not necessary to the achievement of the function or objectives of the compositions, methods, and articles.

[0059] As used herein, “a,” “an,” “the,” and “at least one” do not denote a limitation of quantity, and are intended to cover both the singular and plural, unless the context clearly indicates otherwise. For example, “an element” has the same meaning as “at least one element,” unless the context clearly indicates otherwise. The term “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like. Also, “at least one of” means that the list is inclusive of each element individually, as well as combinations of two or more elements of the list, and combinations of at least one element of the list with like elements not named.

[0060] The term “or” means “and/or” unless clearly indicated otherwise by context. Reference throughout the specification to “an embodiment”, “another embodiment”, “some embodiment”, and so forth, means that a particular element (e.g., feature, structure, step, or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

[0061] The endpoints of all ranges directed to the same component or property are inclusive of the endpoints, are independently combinable, and include all intermediate points and ranges. For example, ranges of “up to 25% by weight, or 5 to 20% by weight” is inclusive of the endpoints and all intermediate values of the ranges of “5 to 25% by weight,” such as 10 to 23% by weight, etc.

[0062] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this disclosure belongs.

[0063] While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.