Natural Composite Infill Material for Synthetic Turf

This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63/652,273, filed on May 28, 2024, entitled “Natural Composite Infill Material for Synthetic Turf”, incorporated herein by reference in its entirety.

Artificial turf fields are composed of three primary components—from bottom to top: Shock pad, carpet, and infill. These components are generally assembled on top of a base of compacted stone. The shock pad is optional and serves to convey much of the shock absorption performance of the turf field, required for the safety of those playing on the surface in the case of impact with the surface. The carpet serves to mimic the blades of grass and root zone, conveying the softness and traction of the surface as well as many of the ball interaction properties. The infill is generally constituted of at least two layers, the bottom layer of which serves to weight down and stabilize the carpets that it is laid onto, whereas the top layers serve as an additional interface layer to those playing on the field, conveying surface softness, friction, traction, and much of the mechanical properties of the field that are felt directly by the players.

The bottom, stabilizing infill is most often sand, and serves to weigh down the turf carpet and keep it in place, as well as providing a more compact and solid base that conveys much traction to the overall turf assembly. Other materials have also previously been used as stabilizing infill, but these remain limited in their pervasiveness due to the good performance, widespread availability, and low price of sand for this purpose.

The upper layers of infill have most often comprised styrene-butadiene rubber (SBR) particles due to the ready availability of end-of-life rubber from car tires, and in many places in the world this continues to be the most commonly used infill material due to shock absorption properties, and its ease of combination with other materials into a complete system. Other types of rubber, such as ethylene propylene diene monomer (EPDM) rubber are also used for this purpose as they are generated as waste from other industries; these can be processed into performance infill to convey advantageous properties; other thermoplastics such as polyvinyl chloride (PVC) have also been used to similar effect. Composite materials can be used that combine thermoplastics, elastomers, reinforcements or fillers to obtain further properties that are difficult to obtain with monolithic materials.

Rising environmental and sustainability concerns have more recently led to the use of alternate materials to replace plastic and rubber infill materials. One approach to these environmental issues has been to produce biodegradable plastic infill materials to alleviate these concerns. However, these materials are difficult to formulate and expensive to produce with the desired properties, and in the quantities required.

The other main approach to mitigate the environmental issues has been to use biological-microbial-, plant- or animal-derived-materials as infills. Cork has been the most common of this type of material used as a performance infill. Cork can provide mechanical performance characteristics, but its low density makes cork expensive to transport and can also lead to it floating off the fields in the case of heavy rain. Cork also includes relatively low wear resistance and limited availability due to long production times and limited growth region. Pulverized olive pits provide mechanical resistance, and are available at low cost, but exhibit a high coefficient of friction that is oftentimes counter to player comfort. Coconut coir has good mechanical performance but requires constant watering to maintain its properties and performance. Other types of lignocellulosic infills such as wood or corn cob granules have also been used, as well as mixed organic materials have also been used as performance infills; while these materials perform well for a time, they can be prone to a more rapid degradation of performance due to their biological nature. While others have explored the use of curable oils as part of the organic infill blends in order to extend the durability of these materials in outdoor conditions but are ultimately just surface treated natural infill materials.

The following presents a simplified summary to provide a basic understanding of some aspects of the disclosed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description presented later.

There remains a need for environmentally friendly, biobased, and ultimately biodegradable infill materials that present good mechanical properties and mechanical resistance, while presenting high availability, easy transportation, and low cost.

In aspects, a basis of the proposed infill is a mixture of natural curable oils, natural hydrophobic polymers, and natural or biological filler that are combined and processed minimally to form a natural composite granule. This granule exhibits the desired performance and durability properties expected of a synthetic turf infill while remaining fully biological and natural.

These and other systems, methods, objects, features, and advantages of the present disclosure will be apparent to those skilled in the art from the following detailed description of the preferred embodiment and the drawings.

All documents mentioned herein are hereby incorporated in their entirety by reference. References to items in the singular should be understood to include items in the plural, and vice versa, unless explicitly stated otherwise or clear from the text. Grammatical conjunctions are intended to express any and all disjunctive and conjunctive combinations of conjoined clauses, sentences, words, and the like, unless otherwise stated or clear from the context.

Various aspects of the subject disclosure are now described in more detail with reference to the annexed drawings, wherein like numerals generally refer to like or corresponding elements throughout. It should be understood, however, that the drawings and detailed description relating thereto are not intended to limit the claimed subject matter to the particular form disclosed. Instead, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the described and claimed subject matter.

For the purposes of this description the word “natural” is used to describe a material that comes from biological or naturally occurring mineral systems, and while it is separated from other materials of a different composition, it is not substantially modified and retains a chemical nature that can be found in the environment without the intervention of man. It is to be understood that “natural” is to include, but not limited to, unprocessed raw materials as well as those extracted and unmodified. Similarly, the word “organic” is meant to describe a carbon-based material, as opposed to referring to the method of growing and harvesting the organism.

An artificial turf system can use an infill material that includes a fully natural composite granular material. In aspects, a stabilizing layer, such as sand or other sufficient material, is incorporated. Moreover, and most often, a shock pad is employed to achieve a desired shock absorption in accordance with a particular installation/purpose. The infill material conveys many of the mechanical properties that are desired for the use as artificial turf infill and conveys performance advantages over the materials and methods described above.

In aspects, the natural composite granular material is made from a blend of one or many natural curative oils such as siccative oils, one or many hydrophobic and optionally curable natural polymers, and one or many reinforcements or filler, mineral or organic natural materials.

In embodiments, the natural composite granular material is composed of 30-95% curable oil, 10-40% hydrophobic natural polymer, and 0-50% filler or reinforcement (percentages are based on the weight of the natural composite granular material). In some embodiments, the natural composite granular material is composed of 40-80% curable oil, 15-30% hydrophobic polymer and 5-20% filler or reinforcement. The amount of curable oil is preferably 60-75%. The amount of the hydrophobic polymer is preferably 15-25%.

The natural curative oils, which are also known as siccative oils used in this composition are oils that polymerize through an oxidation process and harden with exposure to light and oxygen. The curable oils used for this formulation are among linseed oil, tung oil, soybean oil, sunflower oil, safflower oil, poppy seed oil,oil, rapeseed oil, and walnut oil. Linseed oil is particularly and often used.

The natural hydrophobic or curable polymer are among carnauba wax, shellac, dammar, copal, or resins and terpenoid polymers such as rosin-gum rosin (colophony) or other conifer materials-propolis, mastic, tree gums-guaiacum, dammar, kauri, gutta-percha or other natural polymeric blended materials that are hydrophobic and prone to drying.

The reinforcements used are among the categories of natural fibers, such as jute, hemp, linen, coconut coir, cotton, regenerated cellulose, bamboo. In most aspects, these must be of a small size, at most 90% length of the granule diameter. Longer fibers convey greater reinforcement of mechanical strength, but increase the abrasiveness of the material, which is deleterious for use in turf. The fillers used are of a mineral nature, and are selected among standard fillers, such as calcium carbonate, talc, barium sulfate, titanium oxides, silicon dioxides, aluminum oxides, clay, and chalks. Calcium carbonate may be from mineral sources or biogenic sources. In case of calcium carbonate from biogenic sources it is possible to provide a composite granular material from 100% renewable materials. Hydrated lime and stearic calcium carbonate, which may be, are also useful. A mix of calcium carbonate and stearic acid also known as stearic calcium carbonate is often employed.

In an embodiment, the oil is linseed oil, the polymer is rosin and the filler is an inorganic filler. In another embodiment, the natural composite granular material is composed of 30-95, preferably 40-80% linseed oil, 10-40%, preferably 15-30% pine rosin, 0-50%, preferably 0-25% calcium carbonate, and 0-50%, preferably 0-25% talc. In yet another embodiment, the composition comprises 60 to 75%, such as 67% linseed oil, 15 to 25%, such as 20% pine rosin, 8 to 10% calcium carbonate, 3% stearic calcium carbonate and 1% hydrated lime. In a reactor, raw materials are mixed and an oxidation process occurs. Precise setting and monitoring and of air flow and temperature during all oxidation process can be adjusted according to individual needs, whereby the skilled person appreciates that a high air flow and high temperature produces a harder product than a low temperature and a low air flow. Products have a hardness in the order of Shore A 20-40, such as Shore A 30 are preferred.

In some embodiments, a large amount of siccative oil and mineral filler, and a longer residence time in the reactor could lead to a harder and more durable material more apt for use as stabilizing infill, whereas a mix that is less prone to crosslinking and hardening would better maintain its elastics properties and be more appropriate for use as performance infill.

Reaction parameters including air flow, shear and mixing rate, reactor blade size and cross-sectional area, overall size, temperature, and residence time also an effect on the properties of the resulting material. Oxidation process can last up to 15 hours and the product obtained has the aspect of crumbs with granules of several sizes.

Granules obtained from the reactor are then sieved to obtain the required particles size distribution for use in an infill system. In embodiments, particles fall within the range of 0.8-3.15 mm. The granules are produced to have an average particle size in the range of 0.1-5 mm, more preferably a size between 0.3-3 mm, most preferably between 0.8 and 1.25. A fraction wherein 90 wt.-% or more of the granules have size (by sieving) of 0.5 mm or more, is preferred. Granules smaller than 3.15 mm are preferred. The density of the composite granules is in the order of 0.5 g/cmor more, preferably above 0.6 g/cm.

The natural composite infill material is to be used as stabilizing infill or performance infill layer in an artificial turf system.

In aspects, a natural composite infill employs a shock pad to achieve a desired and/or proper shock absorption on the turf. The curable oil-based infill is most often installed over a layer of sand wherein the sand acts as a stabilizing infill. As a stabilizing infill, the sand performs as a ballast layer that weighs down the turf carpets and mitigates movement.

In other aspects, an infill composition for artificial turf fields comprises at least one layer of natural composite infill particles. As previously stated, a shock pad is most often employed to achieve a desired shock absorption of the field.

To the accomplishment of the foregoing and related ends, certain illustrative aspects of the claimed subject matter are described herein in connection with the following description and the annexed drawings. These aspects indicate various ways in which the subject matter may be practiced, all of which are intended to be within the scope of the disclosed subject matter. Other advantages and novel features may become apparent from the following detailed description when considered in conjunction with the drawings.

As stated, the natural composite infill material can be used in combination with a shock pad, carpet, and/or a stabilizing infill layer (e.g., sand) to make up the artificial turf system. The artificial turf system, using the described infill material, exhibits superior mechanical performance, a greater mechanical durability, easy availability and mitigates or otherwise avoids issues of floating away when subjected to large amounts of water.

As a general matter, various types of infill arrangements are contemplated. For example, two layer, three layers, or other arrangements are contemplated. For convenience, the present description primarily discusses two and three layer embodiments. Embodiments of the present disclosure are directed to providing natural composite infill solutions. The materials that are discussed are primarily sand (as a stabilizing infill) and natural composite infill material but it should be understood that other materials can be included or substituted.

As described herein, the infill material is directed to having the natural composite particles, in effect, replace crumb rubber infill materials. As such, the infill is devoid or substantially devoid of crumb rubber or similar materials. For example, in such embodiments, one layer of the infill (e.g., one of the multiple layers in the infill) can be made entirely (100% by weight), substantially (e.g., 65% or higher or 75% or higher by weight), primarily (e.g., 50% or higher by weight), or predominantly (e.g., 45% or higher by weight, or a percentage by weight that is higher than the percentage by weight of any other particle or sand in the same layer) of the natural composite particles. In some embodiments, the infill can be only one layer, and the only layer can be made entirely (100% by weight), substantially (e.g., 65% or higher or 75% or higher by weight), primarily (e.g., 50% or higher by weight), or predominantly (e.g., 45% or higher by weight, or a percentage by weight that is higher than the percentage by weight of any other particle or sand in the layer) of natural composite particles. It is to be understood and appreciated that the natural composite particles can provide shock absorbency and traction. It is possible for the infill layer to include other organic materials or other materials in addition to or in place of those described herein.

The infill may comprise the aforementioned natural composite particles and sand (as a stabilizing layer) in separate layers (one overlaying the other) or intermixed as shown in.depicts illustrative infillcomprising particles and sand in separate layers in accordance with aspects of the innovation. The first layer(sequentially in the order of layers from bottom to top, where bottom is closest to the ground) is preferably a sand layer. In a second layer, the infill may comprise particles in accordance the innovation described herein of a desired engineered size and distribution. The second layermay comprise the aforementioned particles, the aforementioned fine sand, or a combination thereof. When the second layerincludes both the innovative particles and the sand, the innovative particles and the sand are preferably intermixed.depicts illustrative infillcomprising a layerof innovative particles and sand intermixed.

While specific embodiments are shown and described herein, it is contemplated that alternative embodiments exist that employ alternative materials, mixtures, proportions, sizes, etc. without departing from the spirit and/or scope of the innovation as described in detail. These alternative embodiments are to be included within the spirit and scope of the innovation as described and claimed herein.

A composite granular material with a grain size of 0.5-2.5 mm (determined by sieving) and a density of 0.612 g/cmwith a composition as set forth in Table 1 was tested according to EN 15330-5:

The test was conducted with the device shown in. The studded rollers are moved over the artificial turf. The results are shown in. The composite granulate material described above resists 4500 cycles, whereby the minimum requirement in this test is only 500 cycles. At 4500 cycles, 63% of the grains are within the declared values. At 5000 cycles only 56% are within the declared values (requirement est≥60%).illustrates the tested material after 4500 cycles.