WO2005073297A1

WO2005073297A1 - Compaction expanded material for synthetic lawn, production process for the same and use

Info

Publication number: WO2005073297A1
Application number: PCT/IT2004/000030
Authority: WO
Inventors: Riccardo Pasinetti
Original assignee: Franplast S.R.L.
Priority date: 2004-01-30
Filing date: 2004-01-30
Publication date: 2005-08-11

Abstract

The present invention relates to a porous expanded compaction material for a synthetic lawn and to a process for producing the same. Furthermore, the present invention relates to the use of said material to give elasticity to a synthetic lawn.

Description

"COMPACTION EXPANDED MATERIAL FOR SYNTHETIC LAWN, PRODUCTION PROCESS FOR THE SAME AND USE" DESCRIPTION The present invention relates to an expanded^' corαpac- ' tion material for a synthetic lawn and to a process for producing the same. Furthermore, the present invention relates to the use of said material to give elasticity to an artificial or synthetic lawn. Floorings for sports grounds consisting of synthetic lawns made of fibers, for 'instance polypropylene fibers^' connected onto a support, for instance by knotting, have been known for a long time. The kind of flooring now described, made of fibers knotted or connected onto a support, can withdraw given amounts of silica sand. The sand used has a controlled granulome- try that can spread uniformly among the fibers constituting the synthetic lawn and keep them in vertical position, so as to give the sports ground the appearance of a real "natural lawn" . The aforesaid flooring for sports grounds made of a synthetic lawn and sand as compaction material, is an extremely stiff flooring, which can sometimes be dangerous for players performing sports activities. As a matter of fact, the high stiffness of the surface made of synthetic grass and sand cannot protect the joints of the players' legs and neither can it soften and reduce the damages which said players can get if they fall down during sports activities due to the low shock absorption of said lawn. In order to overcome the drawbacks due to a high stiffness of the surface made of synthetic grass and sand particular grounds containing particular compaction materials have been developed. It is known about the use of silica sand and granules of elastic material as compaction material for a lawn made of synthetic grass.

For instance, natural or synthetic rubber in granular form, having a granulometry of about 0.05 to 2 mm, can be chosen as elastic material.

It is known that a natural or synthetic rubber is a polymeric material with elastic properties that are typical of a thermosetting elastomeric material. As a matter of fact, the term elastomer refers to a polymeric material with an elastic behavior, i.e. recovering strains due to an external stress and bringing the final shape of the manufactured item always back to the starting shape, even when the aforesaid strains are very high. Such description helps to dis- tinguish the aforesaid elastomeric materials from plastic materials or "plastomers" .

It is known that a thermosetting (or vulcanized) elastomer, commonly referred to as "rubber", has particular properties allowing its use in several applica- tions .

For instance, a thermosetting elastomer undergoes an irreversible chemical modification (vulcanization)during its transformation to obtain a manufactured item (for instance car tires) . A thermosetting elastomer is at first in a liquid/viscous state and, after being reticulated, cannot be worked a second time, for instance for a possible after-use, since it cannot be brought back to its viscous state. A thermosetting elastomer to be re-used ^"at the end of its lifetime must necessarily be ground, thus limiting its possible use. Alternatively, said material can be disposed of in a dump or in a burner. For such reasons a thermosetting elastomer cannot be regarded as a re- cyclable or "environmentally friendly" material. The use of a compaction material comprising sand mixed with granules of natural or synthetic rubber has some drawbacks . A first drawback consists in that synthetic rubber, for instance block styrene-butadiene rubber (SBR) , has a low skin compatibility and can give rise to skin intolerance or allergies. Moreover, some vulcanized rubbers show a further draw- back due to their black color. Such color limits the possibility of subsequently dyeing the compaction material with colors traditionally used for sports grounds such as green and white. The possibility of dyeing with typical colors used in sports competitions is important in order to give the synthetic surface a higher naturalness and an appearance resembling more a real lawn for sports activities. Furthermore, a compaction material made of natural or synthetic rubber is used as crushed material. Said material is obtained by grinding, chopping, shaking or cutting semifinished products made of rubber or manufactured items made of recycled rubber meant at first for a different use, such as for instance truck tires . Said working steps result in a ground material having a non-uniform granulometry value together with a fraction made of powder.

Therefore, a grinding or chopping step allows to obtain also a fraction made of rubber powder which, if used as compaction material for a synthetic lawn, has the drawback of resulting in a powder-like ground. Another drawback of a compaction material made of natural or synthetic rubber is due to the fact that said material cannot be recycled and is a potential source of environmental pollution at the end of its lifetime .

Finally, as everybody knows, compaction materials made of synthetic rubber stink above all if the ground is placed in a hot climate.

Furthermore, compaction made with crushed rubber obtained from recycled tires is a potential source of water pollution due to the release of heavy metals. Therefore, today it is known about the use of a ther- mosetting compaction material (for instance natural or synthetic rubber obtained by irreversible chemical reticulation, vulcanization) that has some drawbacks among which: toxicity, negative anallergicity, dark color, evil smell (stinking) and non-recyclability at lifetime end.

Moreover, the materials that are available today do not face, and therefore do not solve, the technical problem of keeping the temperature of the synthetic lawn at acceptable values, thus avoiding the phenome- non of over-heating of said synthetic lawn.

A heating of the synthetic lawn to too high temperature values affects the players' condition, since the temperature of their foot soles could increase and give rise to a troublesome sensation. Furthermore, a heating of the synthetic surface increases the wear speed of the surface.

Therefore, there is the need to keep the temperature of the synthetic lawn within a range of acceptable values . Eventually, the materials that are available today do not face, and therefore do not solve, the technical problem connected to too great an accumulation of electrostatic charge on the synthetic lawn. In practice, the components of the synthetic lawn understood as synthetic grass, filling materials (sand) and compaction material, all have insulating electric properties enabling to generate a difference of electric potential between the reference electric potential (ground) and the electric potential of the bodies moving on the surface of the synthetic lawn. Therefore, it should be avoided that an excess of electrostatic charge accumulates on the surface, which could be troublesome for players due to light dis- charges that could be perceived when getting in contact with grounded parts of sports equipment. Finally, today it is not known about the use of an expanded compaction material for a synthetic lawn comprising a porous expanded material in granular form including several premixed components, each component having a chosen granulometry value, a specific density value and a lenticular granule shape with a specific value of the granule thickness/width ratio. Therefore, there is the need for a compaction material for a synthetic lawn that does not have the drawbacks of prior art.

In particular, there is the need for a compaction material for a synthetic lawn that, once laid, can ensure a temperature control of the synthetic surface. Moreover, there is the need for a compaction material for a synthetic lawn that can dissipate an excess of electrostatic charge, if present, thus preventing too great an accumulation thereof on the synthetic surface. Furthermore, there is the need for a compaction material for a synthetic lawn having a lower skin abra- siveness, which is waterproof, ozone-proof, stable to UV-rays so as to ensure a long lifetime of sports grounds. Eventually, the compaction material should be "ecolo- gic", i.e. it should be recyclable and environmentally friendly. The present invention therefore aims at carrying out a porous expanded compaction material for synthetic lawns that is anallergic, not toxic for players and for the environment and recyclable. Another aim of the invention is to carry out a porous expanded compaction material for synthetic lawns that can be dyed with colors used in sports grounds, that has a uniform granulometry and is easy to use. A further aim is to -carry out a porous expanded compaction material for synthetic lawns that can be laid in mixture with sand or alternatively with another ma- terial (other than sand) made of polyethylene or polypropylene obtained from recycling operations , or alternatively with sand and recycled material. A still further aim is to carry out a porous expanded compaction material for synthetic lawns that can be laid alone, for instance by bedding onto a layer made of sand or alternatively onto a layer made off a polyethylene or polypropylene material obtained f_rrom recycling operations. Still another aim is to carry out a porous expanded compaction material for synthetic lawns with different granulometry values, which can be laid alone without using any other material. Another important aim is to carry out a porous ex- , panded compaction material for synthetic lawns whose density and elasticity degree can be varied depending on needs without damaging the elasticity of ±ts fiber and the laying of the synthetic lawn. Still another aim is to carry out a porous expanded compaction material for synthetic lawns whose size is constant, uniform and having an average granulometry of 1.4 to 3.8 mm, a granule apparent density value of 0.4 to 1.0 g/cm³, and a lenticular granule shape with a specific value of granule thickness/width ratio, so as to ensure a temperature control of the synthetic lawn and, at the same time, a low accumulation of electrostatic charge on the surface.

A further aim is to carry out a compaction material ^' for synthetic lawns with a natural smell so as to give the playing environment a greater naturalness, by covering the typical smell of polymers which the various components of the synthetic grass system are made of through the use of perfumed essences. A further aim- is to carry out a compaction material for ^'synthetic lawns whose damping properties of the elastic energy associated to the various playing situations are increased thanks to the . addition of specific thermoplastic elastomers having a terpoly- meric nature characterized by two styrene blocks and a vinyl-polyisoprene block, the latter being hydrogen- ated if necessary.

Finally, a further aim is to carry out a compaction material for synthetic lawns whose self-extinguishing degree and degree of smoke toxicity can be varied ac- cording to ^'normative needs.

These and other aims that will be evident from the following detailed description are achieved by the Applicant, who proposes a porous expanded compaction material for a synthetic lawn comprising an elastomer, characterized in that said material comprises at least a thermoplastic elastomer.

A first object of the present invention is therefore a porous expanded compaction material for a synthetic lawn having the characteristics as in the appended in- dependent claim.

A further object of the present invention is a process for producing a porous expanded compaction material, whose characteristics are listed in the appended inde- pendent claim.

The Applicant has found it useful to select among elastomeric polymeric materials thermoplastic materials . Furthermore, elastomeric thermoplastic materials are molded at a given temperature in their viscous state and show their elastic properties simply thanks to cooling. Said materials, if necessary, can then be molded again by simply starting a new transformation cycle at a given temperature .- By way of summary, we can say that thermosetting elastomers at the state of the art are obtained from an irreversible chemical reticulation and thermoplastic elastomers according to the present invention are obtained from a reversible physical reticulation (by cooling) .

Advantageously, said thermoplastic elastomer are chosen among block styrene elastomers (SBC) . Preferably, said block styrene elastomers are hydrogenated. Advantageously, said hydrogenated block styrene elastomers are chosen from the group comprising: Styrene- Ethylene-Butylene-Styrene, (SEBS) , Styrene-Ethylene- Propylene-Styrene, (SEPS), Styrene-Ethylene-Ethylene- Styrene, (SEEPS) and Styrene-Vinyl-Polyisoprene (hy- drogenate if necessary) -Styrene.

In a preferred embodiment of the present invention, the thermoplastic elastomer further comprises at least a thermoplastic copolymer chosen from the group comprising: Ethylene-Vinyl Acetate (EVA) and Ethylene- Butyl Acetate (EBA) .

Moreover, the thermoplastic elastomer can comprise in addition or alternatively a polymer chosen among polypropylene, polyethylene or other polyolefinic ate- rial .

Furthermore, said thermoplastic elastomer can comprise an antistatic agent, a diluting oil, lubricating and/or slipping additives, process additives, antioxi- dants, anti-UV filters. Moreover, said thermoplastic elastomer can comprise an. inert filler such as for instance calcium carbonate; preferably in an amount of 20 to 60% by weight with. respect to the total weight of the compaction material. The antistatic agent is chosen among ethoxylated amines and glyceryl monostearates and is present in an. amount of 0.2 to 1.5% by weight.

Advantageously, the material according to the present invention is in granular form, said granules having a particular geometry.

For instance, the granule is spheroid or lenticular, i.e. it has a slightly flat appearance. The lenticular granule placed on a plane surface will be in contact with the surface with its greater size (granule width) , whereas its smaller size will be its thickness (granule thickness) . Defining as linear size the maximum linear size of the granule preferably, the thickness/linear size ratio is of 0.2 to 0.8. Said values are obviously to be regarded as distributed over a range, since perfectly identical granules cannot always be obtained. A given value of thickness/linear size ratio gives the compaction material a higher stability thanks to a condition of maximum compaction in a given volume. The higher stability of the compaction material can be explained as the tendency of the particles to stay motionless (after being laid) and to limit their movements after being struck by a ball or as a consequence of stresses caused by players. In practice, a given value of thickness/linear size ratio of the granule having a flat lenticular geometrical shape increases the apparent density value of the material (apparent density = material mass/volume occupied by granular material) . The mass of the mate- rial being the same, its volume shall vary depending on the geometrical shape of the granule. Therefore, the mass of the material being the same, a geometrical shape of the latter enabling a higher compaction shall occupy a smaller volume and thus have a higher apparent density value.

Advantageously, the material according to the present invention is in the form of a porous expanded thermoplastic material. Preferably, chemical or physical expanding agents are used.

For instance, said chemical expanding agent is chosen among azodicarboamides or other solid agents having an expanding effect due to transformation temperatures of the_. compound, in an amount of 0.2 to 3% by mass on the total compound volume.

For instance, said physical expanding agent is chosen among nitrogen gas or other gases injected into the compound in an amount of 5 an 60% by volume on the total compound volume . The material according to the present invention is a porous expanded material.

Material expansion during the extrusion step helps to reduce material density as mass/volume. The porous expanded material has a given intrinsic po- rosity resulting in particular features on granule surface .

The porous material has a higher tendency to trap water, for instance water poured onto the playing ground, for instance trapped as moisture, with respect to a similar non-expanded material. Evaporation latent heat associated with moisture trapped by the synthetic surface enables to keep the temperature of the synthetic lawn at a lower value than a surface compacted with a non-expanded or compact material.

Temperature control enables to avoid a over-heating of the synthetic lawn, thus reducing rolling friction phenomena due to ball rolling as well as reducing sliding friction phenomena due to players sliding in- tentionally or unintentionally on the lawn, reducing ageing lawn speed thanks to a lower global temperature of the synthetic grass system and to a lower temperature of players' foot soles. In practice, the porous expanded material allows to obtain an average temperature of the synthetic lawn, suitably watered through rain or artificial systems, that is lower and more constant with respect to a synthetic lawn compacted with a non-expanded or compact material, given the same exposure to sunlight. The porous expanded material also enables to avoid too great an accumulation of electrostatic charge on the surface of the synthetic lawn.

This result is achieved thanks to the intrinsic porosity of the granule, since a porous granule absorbs wa- ter, in form of moisture, in a higher amount than a non-expanded granule. The higher adsorbed water content helps to dissipate electrostatic charge, if accumulated on the surface, thus preventing an accumulation thereof. Moreover, the use of antistatic agents in the material further helps to achieve this purpose.

A preferred embodiment of the present invention envisages to carry out an expanded compaction material for synthetic lawns that can be laid as a mixture comprising: a) at least an expanded elastomer + inorganic filler (calcium carbonate, talcum, other) and/or organic filler (cork, cellulose filler in particles and o- ther) ; b) at least an expanded elastomer + another polyethylene or polypropylene material, and/or organic filler; c) at least an expanded elastomer + sand + another polyethylene or polypropylene material, and/or organic filler.

Advantageously, the polyethylene or polypropylene material is a material obtained from recycling operations in case there are no compound non-toxicity re- quirements.

Advantageously, the thermoplastic elastomer is a porous expanded material .

The porous expanded material having a flat lenticular geometry can be laid as a mixture of components, each (bimodal or trimodal distribution) having its own granulometry value or thickness/linear size ratio. The advantage resulting from such a distribution is a higher stability of compaction material. Preferably, the fraction having a thickness below 0.5 mm (powder fraction) should be less than 1% on the total .

For instance, in a bimodal distribution a first component could comprise granules with a smaller size of ^"1.0 to 2.5 mm and a second component with a greater size of 2.0 to 4.0 mm. For instance, said first and second component could be mixed together in a ratio of 1:10 to 10:1 depending on desired stability properties.

Another preferred embodiment of the present invention envisages to carry out a compaction material for synthetic lawns comprising a layer made with at least an expanded thermoplastic elastomer, said layer being laid alone by bedding onto another layer made of sand and/or other compaction material (cork or bark) ; or alternatively, onto a layer made with a polyethylene or polypropylene material obtained from recycling operations .

Another preferred embodiment of the present invention envisages to carry out a compaction material for syn- thetic lawns consisting of at least a layer made with at least an expanded thermoplastic elastomer according to the present invention, having a variable granulometry value; said at least one layer being laid alone without using any other material. For instance, a given amount of sand having a given granulometry can be laid onto a surface made of synthetic fibers.

Then a given amount of expanded thermoplastic elastomer in granular form can be laid onto said layer of sand, so as to obtain a compact layer.

In a preferred embodiment, the compaction material can comprise an elastomeric material according to the present invention having two different granulometry values, for instance a small fraction having a size of 1.0 to 2.5 mm and a larger fraction having a greater size of 2.0 to 4.0 mm.

The amount of thermoplastic elastomer used as compaction material varies depending on the elastic properties to be given to the sports ground. A further object of the present invention is a method for giving elasticity to a synthetic lawn, whose characteristics are listed in the appended independent claim. In practice, in an embodiment the Applicant has improved a method for giving elasticity to synthetic lawns comprising an inorganic material, such as for instance silica sand or quartz sand with controlled granulometry, which includes a step consisting in in- troducing directly among the fibers constituting the synthetic grass of a lawn the thermoplastic elastomer in granular form according to the present invention. In a second embodiment the Applicant has improved a method for giving elasticity to synthetic lawns, which includes a step consisting in introducing directly among the fibers constituting the synthetic grass of a lawn only one thermoplastic elastomer in granular form according to the present invention. Advantageously, said thermoplastic elastomer is ex- panded.

Advantageously, said thermoplastic elastomer is mixed with an organic filler (cork) .

The introduced amount of elastomer is of 5 to 30 kg/square meter of ground. In the case of an expanded thermoplastic elastomer, the introduced amount is of 5 to 20 kg/ square meter of ground.

The elastomeric material according to the present invention has the peculiar characteristics of an elastic material, which justify its use for compacting synthetic lawns: deformability, recovery of strains, shock absorbing power, rebounding properties, draining properties and sealing by surface friction. Moreover, the elastomeric material according to the ^• present invention has a high degree of elasticity and of shock absorbing power so as to be skin-friendly or anyway not irritating in case of skin contact -. also violent - and anallergic. A further object of the present invention is a process for producing said elastomeric material. A given amount of at least a thermoplastic elastomer is introduced into a container of a blade mixer; preferably in an amount of 5 to 30% by weight with respect to the total weight of the compaction material. Then a diluting oil can be added, for instance a paraffin oil; preferably in an amount of 10 to 30% by weight. Simultaneously, the mixing step can be started so as to enable the dilution of the elastomer with said oil. Once the dilution is carried out, the other components are then added: - a thermoplastic copolymer, . for instance EVA, in an amount of 5 to 40% by weight; - additives, such as process antioxidant, compatibility agent, lubricating agent and dispersing agent, other antioxidants and anti-UV filters. The inorganic filler can further be added, such as calcium carbonate in an amount of 20 to 60% by weight. Said inorganic filler can be alternatively introduced laterally with respect to the extruder, directly into the melted material after plasticization. The blend of the various components thus obtained is further homogenized in the blade mixer and then intro- duced into a compounding extruder. Within the extruder said blend plasticizes and is ultimately homogenized to be divided into doses, extruded^' and granulated by means of cutting systems . During the-^' extrusion step the blend expands thanks to the expanding agents previously added, thus giving the material an intrinsic porosity.

The material obtained from the process described above is the porous expanded compaction material according to the present invention.

The elastomeric material according to the present invention, thanks to its production process, has a granule surface (surface quality) and an intrinsic sericeous quality (intrinsic characteristic of the ma- terial) that make it less abrasive with, respect to a thermosetting vulcanized elastomer, and anyhow not slipping also in case the sports ground is wet or soaked. Furthermore, by suitably adding the various components and additives it is possible to obtain a compaction material with a natural smell so as to give the playing environment a greater naturalness.

Furthermore, by suitably adding the various components and additives it is possible to obtain a compaction material with fungistatic, bacteriostatic and antimicrobial properties.

Furthermore, by suitably choosing styrene thermoplastic elastomers also among block styrene and vinyl- polyisoprene terpolymers, hydrogenated if necessary, it is possible to obtain a compaction material whose damping properties of the elastic energy due to the various playing situations are increased. Furthermore, by suitably choosing the various components and additives it is possible to obtain self- extinguishing compaction material.

The elastomeric material according to the present invention can be used for compacting all types of sports grounds requiring surfaces with elastic properties. EXAMPLE OF COMPACTION MATERIAL - Thermoplastic elastomer comprising (SEBS) , (SEEPS) and (SEPS) in a 3:1:2 ratio, 12% by weight, with respect to the total of the compaction material;

- Thermoplastic copolymer Εthylene-Vinyl Acetate (EVA) 10% by weight;

- Diluting paraffin oil 20% by weight;

- Calcium carbonate 52% by weight;

- Compatibility/Dispersing agent 0.5% by weight;

- Antioxidant 0.2% by weight; - Lubricating agent (wax) 0.3 by weight; and

- Dye (green) 5% by weight.

EXAMPLE OF EXPANDED COMPACTION MATERIAL

- Thermoplastic elastomer comprising (SEBS) or (SEEPS) or (SEPS) or Styxene-Vinyl-Polyisoprene (hydrogenated if necessary) -Styrene, 13% by weight, with respect to the total of the compaction material;

- Thermoplastic copolymer Ethylene-Vinyl Acetate (EVA) 10% by weight;

- Diluting paraffin oil 20% by weight; - Calcium carbonate .49% by weight;

- Azodicarboamide in powder 1% by weight;

- Glyceryl monostearate 1% by weight; - Compatibility/Dispersing agent 0.5% by weight; -.Antioxidant 0.2% by weight; - Lubricating agent (wax) 0.3 by weight; and

- Dye (green) 5% by weight.

EXAMPLE OF EXPANDED COMPACTION MATERIAL

- Thermoplastic elastomer comprising (SEBS) + (SEEPS) + (SEPS); in a 3:1:2 ratio, 15% by weight, with re- spect to the total of the compaction material;

- Thermoplastic copolymer Ethylene-Butyl Acetate (EBA) 10% by weight;

- Diluting paraffin oil 18% by weight;

- Calcium carbonate 48% by weight; - Azodicarboamide in powder 1.5% by weight;

- Glyceryl monostearate 1% + ethoxylated a ine 0.5% by weight;

- Compatibility/Dispersing agent 0.5% by weight; - Antioxidant 0.2% by weight;

- Lubricating agent (wax) 0.3 by weight; and

- Dye (green) 5% by weight.

EXAMPLE OF COMPACTION MATERIAL + CORK

- Thermoplastic elastomer comprising (SEBS) or (SEPS) , 11% by weight, with respect to the total of the compaction material;

- Thermoplastic copolymer Ethylene-Vinyl Acetate (EVA) 10% by weight;

- Diluting paraffin oil 21% by weight; - Calcium carbonate 42% by weight;

- Finely ground cork 10% by weight;

- Compatibility/Dispersing agent 0.5% by weight;

- Antioxidant 0.2% by weight;

- Lubricating agent (wax) 0.3 by weight; and - Dye (green) 5% by weight.

EXAMPLE OF EXPANDED COMPACTION MATERIAL + CORK

- Thermoplastic elastomer comprising (SEBS) or (SEEPS) or (SEPS) 11% by weight, with respect to the total of the compaction material; - Thermoplastic copolymer Ethylene-Vinyl Acetate (EVA) 10% by weight;

- Diluting paraffin oil 21% by weight;

- Calcium carbonate 40% by weight;

- Azodicarboamide in powder 1% by weight; - Glyceryl monostearate 1% by weight;

- Finely ground cork 10% by weight;

- Compatibility/Dispersing agent 0.5% by weight;

- Antioxidant 0.2% by weight;

- Lubricating agent (wax) 0.3 by weight; and - Dye (green) 5% by weight.

EXAMPLE OF PROCESS FOR PRODUCING EXPANDED ELASTOMERIC MATERIAL

Introduce into a container of a blade mixer a given amount of at least an elastomer chosen among (SEBS) , (SEEPS) _r SEPS) . Add the diluting oil and then mix so as to enable the dilution of the elastomer with said oil. Then add in sequence: thermoplastic copolymer (EVA) and/or (EBA) ; antioxidant, compatibility agent, lubricating agent, dispersing agent, expanding agent, antimicrobial agents, perfumed essences and anti-UV filters -

Add the inorganic filler (calcium carbonate) and/or the organic filler (cork) , which can be alternatively introduced laterally with respect to the extruder, directly into the melted material after plasticization. Introduce the dry blend thus obtained into a compounding extruder. Plasticization of the blend within the extruder and ultimate homogenization.

Extrusion through a spinneret and granulation by means of cutting systems.

During the extrusion step, and in particular during extrusion through the spinneret, because of the sudden pressure drop undergone by the material, the blend expands thanks to the expanding agents previously added, thus giving the material an intrinsic porosity. The thermoplastic elastomer in expanded form has a density of 0.5 to 1.0 g/cm³.

Claims

CLAIMS 1. A porous expanded material for compacting a synthetic lawn comprising at least a hydrogenated block styrene thermoplastic elastomer chosen from the group comprising: Styrene-Ethylene-Butylene-Styrene (SEBS), Styrene-Ethylene-Propylene-Styrene (SEPS) , Styrene- Ethylene-Ethylene-Styrene (SEEPS), Styrene-Vinyl-Poly- isoprene (hydrogenated if necessary) -Styrene .

2. The porous expanded material according to claim 1, characterized in that it further comprises a thermoplastic copolymer chosen from the group comprising: Ethylene-Vinyl Acetate, (EVA) and/or Ethylene-Butyl Acetate, (EBA) .

3. The porous expanded material according to claims 1 • or 2, characterized in that it further comprises: polypropylene and/or polyethylene and/or other poly- olefinic materials .

4. The porous expanded material according to any of the preceding claims, characterized in that it further comprises: an antistatic agent; an expanding agent; a diluting oil, preferably a paraffin oil; additives, such as process antioxidant, compatibility agent, lubricating agent, antimicrobial agent, perfumed essences, self-extinguishing additives (halogenated com- pounds, aluminum hydroxide, magnesium hydroxide), additives having a synergic effect with self- extinguishing additives, dispersing agent, other anti- oxidants, anti-UV filters and dyes.

5. The porous expanded material according to any of the preceding claims, characterized in that it _. further comprises an inorganic filler; preferably calcium carbonate and/or an organic filler; preferably cork.

6. The porous expanded material according to any of the preceding claims, characterized in that it has a density value of 0.5 to 1.0 g/cm³.

7. The porous expanded material according to any of the claims 1 to 6, characterized in that its granules are lenticular in shape with a granule thickness/width

,5 ratio of 0.2 to 0.8. 8. The porous expanded material according to any of the claims 1 to 7, characterized in that its average granulometry is of 1.4 to 3.

8 mm.

9. A process for producing the porous expanded com- 0 paction material according to one or more claims 1 to 8, characterized in that it comprises the following steps : - introduce into a container of a mixer a given amount of at least an elastomer chosen among (SEBS) , (SEEPS) , 5 SEPS) and Styrene-Vinyl-Polyisoprene (hydrogenated if necessary) -Styrene; - add the diluting oil and then mix so as to enable the dilution of the elastomer with said oil; - add a thermoplastic copolymer chosen between (EVA) , 0 (EBA) or a mixture thereof; - add, if necessary, the inorganic filler (calcium carbonate) and/or the organic filler (cork) so as to obtain a homogenous, dry blend; - extrusion and expansion of the homogenous blend so 5 as to obtain the porous expanded material.

10. The process according to claim 9, characterized in that before extrusion one or more additives are added, chosen among: antioxidant, compatibility agent, lubricating agent, dispersing agent, antistatic agent, 0 expanding agent, antimicrobial agents, perfumed essences and anti-UV filters.

11. Use of the porous expanded material according to one or more claims 1 to 8 for compacting a synthetic lawn.

12.^" Use of the porous expanded material according to one or more claims 1 to 8 for giving elasticity to a synthetic lawn.

13. A method for giving elasticity to a surface for sports activities comprising a synthetic lawn, characterized in that said method includes the introduction among the fibers constituting the synthetic lawn of a porous expanded compaction material according to one or more claims 1 to 8 so as to form at least one layer.

14. The method according to claim, 13, characterized in that it includes the introduction among the fibers constituting the synthetic lawn of a filling material, preferably sand or a recycled material, so as to form a first layer onto which a second layer is laid, comprising the porous expanded material according to one or more claims 1 to 8.

15. The method according to claim 13 or 14, characterized in that the layer made of porous expanded ma- erial consists of a bimodal distribution of two fractions of granular materials: a small fraction whose granules have a greater size of 1.0 to 2.5 mm and a large fraction whose granules have a greater size of 2.0 to 4.0^' mm.