Patent Description:
Typically, a synthetic turf consists of a base layer of polymeric or polypropylene material, possibly coupled to one or more insulating layers, to which synthetic filaments are attached that simulate natural turf. Between the filaments, a filler material, called "infill", is generally distributed, comprising a lower stabilizing layer of sand followed by an upper performance layer of granular material that may be synthetic, natural or a mixture of the two.

The infill gives the turf various mechanical and physical characteristics, the composition and laying of which is usually chosen depending on the target sport discipline. These characteristics, in fact, should simulate those of natural turf as much as possible, such as, e.g., elasticity for the user and for ball bounce, shock absorption capacity, tensile strength and resistance to tears caused by shoes, compressive strength, homogeneity, drainage, etc..

There are very many types of infill and related processes described in the state of the art. Generally, the granular material used to fill the infill is recycled thermoplastic synthetic-derived material (such as, e.g., EPDM) or SBR normally obtained from shredding used tires which, however, has obvious negative environmental impacts.

Over the years, alternatives to the classic widely used materials using synthetic rubber granular materials have been investigated by attempting to address towards natural plant materials in fibrous, ground and/or shredded form such as cork, coconut, peat or other plant materials derived from the bark of shrubs and plants as described, for example, in <CIT> and <CIT>.

One problem with using natural/vegetal materials is the low specific gravity value of the various components. In particular, the cork used today in soccer fields, indoor and outdoor sports areas and children's play areas has a specific gravity (measured in granular form) of about <NUM>/cm<NUM> with a tendency, therefore, to float in case of rainfall as well as volatility in case of strong wind that causes it to shift with respect to its original laying position. A problem that is even more evident taking also into account that the fields are curved in such a way as to drain rainwater outwards, an aspect that over time leads to the drift of much of the infill material and thus also of the granules towards the edges of the field.

To overcome these drawbacks, granule coating systems have been developed such as the one described, for example, in <CIT> with the purpose of waterproofing and saturating the pores with natural and/or synthetic one- or two-component resin. However, these solutions, too are ill-suited for real and effective use as the increase in specific gravity is not sufficient to overcome the aforementioned problems of flotation and/or volatility. In addition, coating materials often need to be fortified with substances adapted to make the granules flame retardant, to prevent mold formation and bacterial colonies thus mitigating to some extent the ecological aim of the solution.

Other examples of prior art can be found in documents <CIT>, <CIT>, <CIT> and <CIT>.

Thus, a solution was devised to obtain a filler material coated according to techniques and materials that are as natural as possible and that allows an effective raising of the specific gravity of the cork granule.

Therefore, the present invention relates to a process for the manufacture of filler material for synthetic turf in accordance with claim <NUM>.

An additional object of the present invention relates to a filler material for synthetic turf in accordance with claim <NUM>.

Further characteristics and advantages of the process, the filler material and coating substance in accordance with the present invention will result from the description below of its preferred examples of embodiment.

The process for the manufacture of filler material for synthetic turf uses a coating substance configured to be combined with cork in granular form. In experimental tests carried out, the substance according to the present invention proved to be extremely effective in respecting the physical and mechanical properties of cork. Indeed, as is well known, much of the physical and mechanical properties of cork are due to the structural characteristics at the cell level and to the chemical structure of the plant wall (more than <NUM> percent suberin, lignin and polysaccharides). Untreated granulated cork generally has a specific gravity of <NUM>-<NUM>/cm<NUM> (measured in granular form) and a thermal conductivity of about <NUM> W/(m·K). The main characteristics of untreated cork can be summarized as follows:.

Advantageously, the coating substance configured to be combined with cork in granular form is characterized by a melting value of between <NUM> and <NUM>, preferably between <NUM> and <NUM>.

Preferably, the coating substance has a penetration index between <NUM> and <NUM> at <NUM>, preferably between <NUM> and <NUM>.

In the remainder of this description and in the subsequent claims, "penetration index" means the depth measurement by which a standard-sized needle sinks into a substance under certain conditions of load, time and temperature, dictated by various standards, such as e.g., UNI EN <NUM> or ASTM D1231. The test is carried out using a penetrometer, which applies a load equal to <NUM> for a time of <NUM> seconds at a temperature of <NUM>. The exact temperature of the sample being tested is ensured by dipping it in a thermostatic bath, for a time equal to <NUM> minutes, by means of a thermostatically-controlled cell. This test is used to determine the consistency and hardness of a given substance. The higher the penetration index, the "softer" the substance is considered to be.

Advantageously, the coating substance covered by this invention and configured to be combined with cork is wax.

In the following description and the subsequent claims, the term "wax" comprises materials of different origins and compositions. Generally, materials called "waxes" are sticky solids which melt and exhibit different levels of gloss and plasticity. Waxes are divided into two macro-families, natural waxes and synthetic waxes. The former are differentiated by their extraction, i.e., fossil (petrochemical and from lignite) or non-fossil (animal and plant); the latter are obtained by total or partial chemical synthesis. Waxes of petrochemical origin are commonly called paraffins and may have C20-C60 alkyl, branched alkyl or naphthalene chains. Differently, waxes of animal or plant origin are commonly identified as esters of monohydric alcohols or glycerol esters. In addition, it should be specified that waxes of petrochemical origin have a highly variable chain distribution compared to vegetable or animal waxes.

Preferably, the wax of the invention is natural wax or synthetic wax.

In accordance with one embodiment, natural wax comprises a substance selected from the group comprising: carnauba wax, beeswax, myrtle wax, candelilla wax, rice wax, esparto wax, ouricury wax, spermaceti, Chinese wax, lanolin, shellac, vegetable stearin, paraffins, magnesium stearate, stearic acid or suitable mixtures thereof.

In accordance with one embodiment, synthetic wax comprises a substance selected from the group comprising: paraffins, microcrystalline waxes, polyethylene waxes or suitable mixtures thereof.

In accordance with one embodiment, wax has a melting value of between <NUM> and <NUM>, preferably between <NUM> and <NUM>.

In accordance with another embodiment, wax has a penetration index of between <NUM> and <NUM> at <NUM>, preferably between <NUM> and <NUM>. Preferably, the mass of wax used in the process according to the invention has a specific gravity of about <NUM>/cm<NUM>.

The process covered by the invention comprises a phase of having a predetermined amount of cork material in granular form with a predetermined initial specific gravity and a phase of having a predetermined mass of coating substance as described above.

Preferably, the granulated cork is sourced from Italy.

The mass of coating substance is natural wax, synthetic wax or suitable mixtures thereof.

Preferably, the cork granules are arranged in bags and previously weighed on appropriate load cells. It should be specified that each cork granule has a substantially spherical shape having a diameter of between <NUM> and <NUM>. Additionally, each cork granule has an initial/starting specific gravity having a value of about <NUM>/cm<NUM>, measured with a graduated cylinder.

Via a conveying line, the cork granules are sent towards a mixer.

Conveniently, the wax mass, preferably in the form of blocks or flakes, is placed inside a melting device to be heated until the melting point is reached. The wax is heated to a temperature of between <NUM> and <NUM>, preferably <NUM>. The melting point is reached over a period of <NUM> minutes to <NUM> minutes, preferably <NUM> minutes.

From the melting device, the melted wax is sent via a suitable hydraulic line, configured to keep the wax at temperature, towards the mixer. Conveniently, the hydraulic line terminates with one or more nozzles arranged above the mixer and intended to spray the melted wax against the cork granules.

In accordance with one embodiment, it is possible to provide two or more melting devices connected to each other, preferably in parallel, by suitable valve means so that the sending of the melted wax towards the mixer occurs continuously.

As anticipated above, the nozzles are oriented towards the mixer in order to spray/nebulize/percolate the melted wax above the cork granules while the latter are moved by the mixer. This phase involves mixing the cork material with the wax mass to obtain a granular filler material made of coated cork having a predetermined final specific gravity and thus intended for use in synthetic turf the main characteristics of which will be highlighted later in this detailed description.

Mixing takes place for a period of between <NUM> minutes and <NUM> minutes, preferably <NUM> minutes.

Advantageously, due to the phases in the aforementioned process and to the physical and mechanical properties of the wax, the melted mass is able to distribute and flow over the surface section of the cork granule homogeneously without crystallizing where the melted mass is fed in.

A further phase involves cooling the granular filler material made of coated cork. Specifically, it can be cooled inside the mixer or outside by means of settling tanks.

At the end of the mixing phase, the ratio of the final specific gravity to the initial specific gravity of the cork material is of between <NUM> and <NUM>.

In accordance with one embodiment, the ratio of the final specific gravity to the initial specific gravity of the cork material is of between <NUM> and <NUM>, preferably about <NUM>.

Even more preferably, the ratio of the final specific gravity to the initial specific gravity of the cork material is about <NUM>.

Basically, the specific gravity of the granular filler material made of coated cork has a specific gravity of approximately between <NUM>/cm<NUM> and <NUM>/cm<NUM>, preferably <NUM>/cm<NUM>. The increase of the specific gravity around these values combined with effective drainage of a synthetic turf allows avoiding the classic problems of flotation and volatility inherent in infill with unprocessed cork granules.

Several tests were carried out to verify the actual raising of the specific gravity of the cork granules and to check the physical and mechanical properties of the granular filler material made of coated cork thus obtained.

A first test was carried out by introducing cold (at about <NUM>) into a paddle mixer, <NUM> of cork granules having an initial specific gravity of about <NUM>/cm<NUM>, of Italian origin and with granule diameters ranging from <NUM> to <NUM>. Following rapid stirring, <NUM> of yellow beeswax melted at a temperature of about <NUM> was introduced. After about <NUM> minutes of mixing, the melted mass of wax began to distribute and flow over the surface section of the granule evenly without crystallizing also thanks to the very low thermal conductivity of the cork granules.

A second test was carried out by introducing cold (at about <NUM>) into a paddle mixer, <NUM> of cork granules having an initial specific gravity of about <NUM>/cm<NUM>, of Italian origin and with granule diameters ranging from <NUM> to <NUM>. Following rapid stirring, <NUM> of carnauba wax melted at a temperature of about <NUM> was introduced. After about <NUM> minutes of mixing, the melted mass of wax began to distribute and flow over the surface section of the granule evenly without crystallizing also thanks to the very low thermal conductivity of the cork granules.

In both tests, the waxes had a melting point of about <NUM>, a high penetration index due to the high content of oils and esters with low molecular weight.

In both tests, the resulting granular filler material made of coated cork had:.

In conclusion, this resulted in a granular filler material made of coated cork that is softer and stickier to the touch than the starting cork granule material.

As found by the present description, it has been ascertained that the described invention achieves the intended objects, and in particular, the fact is emphasized that the manufacture of the granular filler material made of cork coated with wax makes it possible to raise the specific weight of the starting cork granulate without, however, altering its physical and mechanical properties ensuring highly effective applicability in synthetic soccer fields, indoor and outdoor sports areas, and children's play areas as well as to obtain a material that is completely eco-sustainable, thus safeguarding the environment and natural resources.

Claim 1:
Process for the manufacture of granular filler material for synthetic turf, comprising
the phases of:
- having cork material in granular form with a predetermined initial specific gravity,
- having a mass of a natural or synthetic wax coating substance with a melting point of between <NUM> and <NUM> and a penetration index of between <NUM> and <NUM> at <NUM>,
- heating said mass of coating substance until it reaches the melting point,
- joining said mass of coating substance to said mass of cork,
- mixing said cork material in granular form with said mass of coating substance to obtain a granular
filler material for synthetic turf with a final specific gravity of the granular filler material of between <NUM>/cm<NUM> and <NUM>/cm<NUM>, preferably <NUM>/cm<NUM>,
- allowing said filler material to cool down.