WO2013060634A1

WO2013060634A1 - Shockpad for artificial turf systems

Info

Publication number: WO2013060634A1
Application number: PCT/EP2012/070837
Authority: WO
Inventors: Arie Hendrik Frans Van Vliet
Original assignee: Bonar B.V.
Priority date: 2011-10-28
Filing date: 2012-10-22
Publication date: 2013-05-02
Also published as: JP2014530974A; EP2771513A1; AU2012327321A1; CN103946452A; NZ623907A

Abstract

A shockpad comprising a three-dimensional entangled mat of extruded filaments made from a thermoplastic elastomeric polymer, especially a thermoplastic elastomeric polyester polymer or a thermoplastic elastomeric polyurethane polymer, provides improved shock absorption and energy restitution in artificial turf systems.

Description

Shockpad for Artificial Turf Systems

Description:

The invention pertains to a shockpad for artificial turf systems. The invention also pertains to artificial turf systems comprising the shockpad.

Artificial turfs or synthetic turfs are known as grass-like man-made surfaces manufactured from synthetic materials such as polyethylene, polypropylene, polyamide and the like. They are most often used in stadiums for sports that were originally or are normally played on natural grass. Artificial turfs are being used on residential lawns and in landscaping applications as well.

The first artificial turf systems for playing sports developed and installed already in the early 60'ies of the 20^th century had a far harder surface than natural grass, and soon became known as an unforgiving playing surface, which was prone to cause more injuries.

In the early 21 ^st century, artificial turf playing surfaces using sand and/or rubber infill were developed. These artificial grass surfaces are often virtually

indistinguishable from natural grass when viewed from a distance, and are generally regarded as being much more safe to play on than the first generation of artificial playing fields.

Many sports clubs have installed new artificial turf systems (most commonly as part of an all-weather training capability), while some clubs, which have maintained natural grass playing surfaces, are now re-considering installing artificial turf systems.

With football clubs looking to reduce both maintenance costs of their playing fields and to reduce the number of winter matches that are cancelled due to frozen pitches, the issue has also been re-visited by that sport's governing bodies, such as UEFA and FIFA.

The most common type of artificial turf system uses synthetic "grass halms", for example made of polyethylene, polypropylene or polyamide, about 5 centimeters long, which are lubricated and tufted into a backing fabric, for example a woven or a nonwoven fabric or a combination of both, the rear of which is coated with a polyurethane or latex backing medium to lock the tufted synthetic grass halms into place. The tufted and coated fabric is then infilled between the tufted synthetic grass halms to the client's specification with sand and/or rubber granules, which keeps the synthetic grass halms upright and provides shock absorbency and deformability for playing sports such as football. The infill layer generally is about 15 to 30 mm thick. The majority of the manufacturers of artificial turf systems approved by FIFA use this technology.

A second type of artificial turf system has a base shock absorbing layer of a polymer foam material placed underneath the tufted and coated fabric. The thickness of the layer of rubber particles and sand in the infill layer can then be reduced due to the presence of the foam material.

Artificial turf systems comprise at least one type of synthetic grass halms, a backing fabric, generally a coating to lock the tufted synthetic grass halms into place, and if applicable infill materials and/or a shock absorbing layer. The football clubs seek to have their playing fields, i.e. the complete artificial turf system, qualified by FIFA. In 2001 the FIFA created universal guidelines for artificial turf football pitches, the so-called FIFA Quality Concept. Based on player's feedback, medical research, test results and information from the industry since the implementation of the FIFA Quality Concept in 2001 , a second, more stringent quality standard has been developed in addition to the existing level, the FIFA Recommended 2 Star rating system.

The quality of an artificial turf system is established by first performing laboratory tests to determine its composition and subsequent testing for durability, joint strength, climatic resistance, player-surface interaction and ball-surface

interaction. In addition, the reaction of the turf to the skin of the players, when sliding on the surface, is measured in form of skin abrasion and friction for the FIFA Recommended 2 Star qualification.

In the second stage, the installed artificial turf system is tested on site. Specialized field-testing equipment measures how the ball reacts on the surface in terms of roll, vertical rebound and how the ball behaves when it strikes the surface at an angle. The artificial turf system is also tested how it reacts to the actions of players, including shock absorbency, surface deformation, slip resistance and traction.

If the artificial turf system passes all the laboratory and field tests, it will qualify for one of the two FIFA Recommended marks. FIFA Recommended 1 Star

qualification allows training and matches on a municipality and national level. FIFA Recommended 2 Star qualification allows matches on the international level.

Artificial turf systems that meet the quality criteria for FIFA Recommended marks combine the advantages of the playing characteristics of natural grass with a high level of comfort and safety for the players.

When a playing field has qualified for the FIFA Recommended 2 Star qualification, the qualification has to be renewed on a yearly basis to ensure that the playing field has retained its high quality after extended use and after being exposed to the environment. It has proven very difficult to retain the FIFA Recommended 2 Star qualification over a prolonged period of time, for example due to deterioration of the shock absorbing performance of the artificial turf system. Artificial turf systems having a base foam layer and having an infill of rubber particles have satisfied the conditions for the FIFA Recommended 2 Star qualification. However, the shock absorbing performance of the foam layer decreases over time with extensive use thereby risking that the FIFA

Recommended 2 Star qualification is revoked upon testing for the yearly renewal.

Artificial turf systems having a foam layer, used as a base shock absorbing layer under the tufted and coated fabric, have a relatively high level of energy restitution compared to natural turf. A high level of energy restitution has a tiring effect on the muscles of the players, which poses an increased risk of injuries.

A foam layer, used as a shock absorbing layer under the tufted and coated fabric, has a limited capability for draining liquid such as water, from the playing field.

Whilst already having advantages over natural grass surfaces, the overall shock absorption and energy restitution characteristics of playing fields are still subject to improvement.

It is an object of the present invention to provide a shockpad providing improved shock absorption and/or energy restitution characteristics to artificial turf systems. It is another object of the invention to provide artificial turf systems having improved shock absorption and/or energy restitution characteristics, especially over a prolonged period of time.

The object of the invention is achieved by a shockpad comprising a three- dimensional entangled mat of extruded filaments made from a thermoplastic elastomeric polymer. Surprisingly, it has been found that the shock absorbing performance of the shockpad enables artificial turf systems to qualify for the FIFA Recommended 1 Star or even the FIFA Recommended 2 Star qualification. Even more surprisingly it has been found that the shock absorbing performance of the shockpad does not deteriorate after extensive use, being subjected to 10.000 loading cycles, to such an extent that the FIFA Recommended qualification of the artificial turf system would be revoked. The inventive shockpad thus ensures that the artificial turf system retains the FIFA Recommended qualification for a prolonged period of time.

The filaments of the three-dimensional entangled mat of extruded filaments are preferably thermally bonded at their crossing points. Thermoplastic elastomeric polymers are a class of copolymers or a class of polymers blends which consists of materials with both thermoplastic and elastomeric properties. The copolymers may be segmented block copolymers consisting of stiff and flexible blocks or may be triblock copolymers of the ABA- type, such as for example a styrene-butadiene-styrene (SBS) copolymer.

Thermoplastic elastomeric polymers may also consist of thermoplastic polymer blended with elastomeric polymer, such as for example a blend of polypropylene and EPDM rubber.

The thermoplastic elastomeric polymer (TPE) may be any type of thermoplastic elastomeric polymer, for example thermoplastic polyolefin elastomeric polymers (TPO) such as for example thermoplastic polypropylene elastomeric polymer, thermoplastic polyester elastomeric polymers (TPC) such as for example sold under the Arnitel and Pibiflex name, thermoplastic styrenic elastomeric polymers (TPS), or thermoplastic elastomeric polyurethane polymers (TPU) such as for example sold under the Elastollan and Desmopan name. When the shockpad is made from thermoplastic elastomeric polyester polymer, the shockpad is especially advantageous to obtain FIFA Recommended 1 Star qualified artificial turf systems. Preferably, the thermoplastic elastomeric polyester polymer comprises stabilizing agents against hydrolysis.

When the shockpad is made from thermoplastic elastomeric polyurethane polymer, the shockpad is especially advantageous to obtain FIFA Recommended 1 Star qualified artificial turf systems and FIFA Recommended 2 Star qualified artificial turf systems, which retain the qualification for a prolonged period of time.

The thermoplastic elastomeric polyurethane polymer of the shockpad may be polyester based thermoplastic elastomeric polyurethane polymer or polyether based thermoplastic elastomeric polyurethane polymer. An advantage of a shockpad comprising a three-dimensional entangled mat of extruded filaments made from a polyether-based thermoplastic elastomeric polyurethane polymer is that the shockpad has high resistance against hydrolysis and thus does not require stabilizing agents for improving resistance against hydrolysis.

The shockpad may of course also advantageously be used as a shockpad under other kinds of playing fields, such as for example tennis courts, hockey fields, rugby pitches, indoor playing fields, such as for example basketball or indoor soccer pitches, or running tracks.

The inventive shockpad further enables the manufacture of artificial turf systems having a level of energy restitution approaching the level of energy restitution of natural grass playing surfaces. Preferably, the three-dimensional entangled mat of extruded filaments has a high void volume to provide the required level of shock absorption, energy restitution and/or drainage capacity. The void volume of the three-dimensional entangled mat of extruded filaments may be at least 50 vol.%, preferably at least 75 vol.%, more preferably at least 85 vol.%, even more preferably at least 90 vol.%, most preferably at least 95 vol.%. Three-dimensional structures of entangled extruded filaments are known, for example from products sold under the Enkamat^® name, however these three-dimensional structures are made from polymeric materials, such as polypropylene (PP) or polyamide-6 (PA6), which are unsuitable to be applied as a shockpad according to the invention. Three-dimensional structures of entangled extruded filaments made from polypropylene are too stiff and have insufficient resilience to be used as a shockpad for artificial turf systems qualifying for a FIFA Recommended qualification. The mechanical properties of three- dimensional structures of entangled extruded filaments made from polyamide-6 are dependent on the humidity of the environment and thus unsuitable to be used as a shockpad according to the invention.

The thickness of the three-dimensional entangled mat of extruded filaments may be in the range of 2 to 30 mm. Preferably, the thickness of the three-dimensional entangled mat of extruded filaments is in the range of 5 to 20 mm, more preferably in the range of 10 to 20 mm to provide the required level of shock absorption and/or energy restitution.

The thickness of the filaments in the three-dimensional entangled mat of extruded filaments may be in the range of 0.1 to 2.5 mm, preferably in the range of 0.2 to 2.0 mm, more preferably in the range of 0.3 to 1 .5 mm, even more preferably in the range of 0.4 to 1 .2 mm, most preferably in the range of 0.5 to 0.8 mm.

The inventive shockpad 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 shockpad may comprise one or more additional layers. Each of the additional layers may be 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.

Each of the additional layers may be physically attached to the three-dimensional entangled mat of extruded filaments and/or another additional layer of the shockpad by any known manner, such as for example by thermal bonding, mechanical bonding and/or adhesive bonding. Alternatively, each of the additional layers may be positioned in a co-planar manner with the three-dimensional entangled mat of extruded filaments without being physically attached to the three- dimensional entangled mat of extruded filaments.

An additional layer may for example provide a protective layer to prevent that filaments from the three-dimensional entangled mat of extruded filaments damage the backing fabric of the artificial turf system and/or to prevent that sand from the infill layer flows through holes in the backing fabric into the shockpad.

An additional layer may for example provide a liquid impervious layer to collect and retain liquid, such as (rain)water, instead of draining the liquid through the sub-surface on which the artificial turf system is placed.

An additional layer may for example provide increased strength and/or

dimensional stability to the shockpad, which facilitates easier placement of the shockpad during installation of the artificial turf system.

The shockpad may optionally comprise infill particles inside the three-dimensional entangled mat of extruded filaments to influence for example the shock absorbing performance, energy restitution and/or deformability of the artificial turf system. Preferably, the shock pad does not comprise infill particles inside the three- dimensional entangled mat of extruded filaments. Shock absorption has been determined in accordance with the Standard Draft Triple A, test method for the determination of force reduction, vertical deformation and energy restitution, September 2010. This Triple A test, also known as the Advanced Artificial Athlete, is an improved method of the FIFA test method 04/05-01 , which is known as the Artificial Athlete. The Triple A test method provides the opportunity to measure force reduction, vertical deformation and energy restitution all at the same time, which was not possible with the FIFA test method 04/05-01 . The shock absorption results of the Triple A test are expected to match the absorption results of the FIFA test method 04/05-01 .

To evaluate the shock absorption, a weight of 20 kg, having a spring with a diameter of 70 mm attached to its lower side, is dropped from a height of 55 mm onto an artificial turf system placed on a concrete foundation layer. The

deceleration of the weight is recorded over the entire impact event. The maximum deceleration of the weight by the artificial turf system is determined and compared to the maximum deceleration of the weight when dropped directly onto the concrete foundation layer. The reduction in the maximum force needed for this deceleration of the weight is called force reduction, and is expressed as a percentage. The higher the percentage of force reduction the softer the surface is, i.e. the more shock absorbing the surface is.

Natural turf in ideal conditions produces force reduction values of between 60 and 70%. The force reduction in the shock absorption test has to be in the range of 55 to 70% for a FIFA RECOMMENDED 1 Star qualification, and has to be in the range of 60 to 70% for obtaining a FIFA RECOMMENDED 2 Star qualification for an artificial turf system.

However, an artificial turf system having a FIFA RECOMMENDED 2 Star qualification for an artificial turf system has to be retested on a yearly basis to retain the FIFA RECOMMENDED 2 Star qualification. The durability of the shock absorbing performance of the shockpad is determined by placing the shockpad used to determine the initial shock absorption in the artificial turf system in a tensile testing machine, and compressing the shockpad at a pressure of 0.7 MPa and releasing the pressure for 10.000 consecutive loading cycles. The compression pressure of 0.7 MPa is applied within 1 second. After reaching the compression pressure of 0.7 MPa, the pressure is immediately released. After 2 seconds the next loading cycle is started. Subsequently, the shock absorption of the shockpad in the artificial turf system is determined again in accordance with the Triple A test.

The vertical rebounce or energy restitution is the energy returned by the (artificial) turf system, and is calculated from the deceleration curve of the Triple A test. Natural turf generally has an energy restitution of about 20 to 25 %.

Example

A thermoplastic polyurethane material (BASF Elastollan 1 174 D1 1 ) was extruded through a spinneret with 100 holes having a diameter of 0.35 mm. The extruded molten filaments are collected on a rotating roll with a profiled surface having pyramidal shaped protrusions of 15 mm height. The rotating roll oscillates in the direction perpendicular to the rotating direction of the roll, i.e. along the axis of the rotating roll. The individual molten filaments fuse together into a three-dimensional filament structure having a weight of 900 g/m² and a width of 25 cm. On both sides of the three-dimensional filament structure a Colback S90 nonwoven is thermally bonded to the structure.

The shockpad thus obtained was tested in a system in which it is positioned below a grass carpet with an infill consisting of 22.5 kg/m² sand particles having a diameter of 0.2 to 1 .0 mm and 7.5 kg/m² TPE granules (Forgrin HT Verde). The test used is described in the draft standard Triple A (September 2010) prepared by the European working group WG1 1 (TC217).

The system was tested with the virgin shockpad and with the shockpad subjected to 10.000 loading cycles at 0.7 MPa. This gave the results as shown in Table 1 .

Table 1

Force Vertical Energy

reduction deformation Restitution

Shockpad (%) (mm) (%)

Virgin shockpad 65.4 8.4 30.2

Shockpad after

10.000 loading 63.9 9.0 32.8

cycles

Claims

Claims:

1 . A three-dimensional entangled mat of extruded filaments made from a

thermoplastic elastomeric polymer.

2. The three-dimensional entangled mat of extruded filaments according to claim 1 characterized in that the thermoplastic elastomeric polymer is a thermoplastic polyurethane elastomeric polymer.

3. The three-dimensional entangled mat of extruded filaments according to claim 2 characterized in that the thermoplastic polyurethane elastomeric polymer is a polyether-based thermoplastic polyurethane elastomeric polymer.

4. The three-dimensional entangled mat of extruded filaments according to claim 1 characterized in that the thermoplastic elastomeric polymer is a thermoplastic polyester elastomeric polymer.

5. A shockpad for artificial turf systems comprising a three-dimensional

entangled mat of extruded filaments according to any of the preceding claims.

6. The shockpad according to claim 5 characterized in that the shockpad

comprises one or more additional layers, each of the additional layers being a film, 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. An artificial turf system comprising a backing fabric, the backing fabric being tufted with at least one type of synthetic grass halms and coated to lock the tufted synthetic grass halms into place, and a shock absorbing layer characterized that the shock absorbing layer is a shockpad according to any of claims 5 to 6.