Patent Description:
Artificial turf has become an increasingly attractive solution for many venues to reduce water consumption, enhance durability, and improve resistance to pet waste. Moreover, in dry conditions, artificial turf provides an 'evergreen' grass-like ground cover. However, mixed artificial grass materials and/or relatively long artificial grass blades require infill materials to stabilize the blades in a substantially natural looking manner and to prevent matting. To that end, several different infills are currently known in the art.

For example, crumb rubber can be used as a filler and is typically produced from recycled tires and so contains a number of known carcinogens. Moreover, due to its black color, the filler material will be very hot when exposed to the sun. Additionally, known rubber-based infill has no significant ammonia neutralization capabilities. Crumb rubber can be coated to render the product more acceptable as described, for example, in <CIT> and <CIT>. However, even with coating, numerous undesirable problems remain-in particular, the undesirable heating and the inability to neutralize ammonia from sources such as urine. Still further, crumb rubber has been suspected to leach toxic chemicals into waterways posing a risk to the environment, animals, and humans.

To avoid potential difficulties with environmental toxicity, silica sand can be used as infill material. Most silica sand is rough and angular in shape, resulting in compaction under pressure, which ultimately will compromise drainage capability. Moreover, most silica sand fillers are prone to dust formation upon installation and use, which may lead to silicosis. In addition, silica sand is known to heat up to undesirably high temperatures under sun exposure. While ceramic materials have been used instead of silica sand as disclosed in <CIT>, dust formation is still problematic, and neither silica sand nor ceramics have ammonia neutralization capabilities.

Alternatively, various organic materials can be used to circumvent issues associated with dust formation. For example, <CIT> discloses composite filler materials comprising coconut shell, matured coconut husk, young coconut shell, young coconut husk, Manila hemp, lignin and cassava. Such materials may further be coated with antimicrobial agents as described in <CIT>. Unfortunately, even with a coating, nut-based fillers may trigger allergic reactions and are still prone to dust formation.

Temperature control of infill materials can be attempted with water-filled superabsorbent materials such as polyacrylamide or polyacrylate as described in <CIT>. Unfortunately, these materials are typically mechanically unstable and require replacement or refill. Alternatively, hollow cylindrical infill material has been used as described in <CIT>, but these materials are typically subject to compaction over time. Still other polymeric fillers are shaped as hollow spheres to provide shock absorption as disclosed in <CIT>. <CIT> discloses an infill material comprising at least an elastomer and at least an additive, which retards the heating of the granulate after exposing to an electromagnetic radiation. The additive is formed from a mineral substrate such as expanded clay, bentonite, montmorillonite, perlite, hydrophilic pyrogenic silicic acid and/or porous concrete.

While such materials avoid at least some of the problems noted above, most or all of them still lack environmental compatibility and ammonia neutralization capabilities. As such, compaction, proper disposal, and/or pet waste remain significant issues.

Thus, even though various infill materials for artificial turf are known in the art, all or almost all of them suffer from various disadvantages. Consequently, there is a need to provide improved compositions and methods for infill materials for artificial turf which are at least environmentally friendly infill materials that resist compaction, provide desirable thermal control, and enable ammonia neutralization.

The inventors have now discovered that aragonite, and especially microporous oolitic aragonite can be used as an infill material for artificial turf that is environmentally friendly, resists compaction, provides desirable thermal control, and enables ammonia neutralization. Moreover, as oolitic aragonite is relatively heavy, it will weigh down artificial grass effectively. Moreover, and as is shown in more detail below, the inventors have observed that oolitic aragonite is approximately <NUM> degrees Celsius (<NUM> degrees Fahrenheit) cooler than typical infill material and advantageously provides ammonia neutralization properties without toxicity or dusting.

In a first aspect of the invention, an artificial turf according to claim <NUM> is provided. It comprises a plurality of turf fibers coupled to a backing to form an artificial turf structure, and microporous oolitic aragonite particles disposed between the turf fibers. Most preferably, the aragonite particles comprise oolitic aragonite, which may be processed to a desired size or size rage (e.g., micronized oolitic aragonite). Thus, in some embodiments the aragonite particles may have an average size of less than <NUM>, or may have an average size of between <NUM> micrometer and <NUM> micrometer. It is further generally preferred that the aragonite particles will have a surface area of at least <NUM><NUM>/g, or at least <NUM><NUM>/g, or at least <NUM><NUM>/g. Additionally, the microporous oolitic aragonite particles have a uniformity constant of between about <NUM> to about <NUM>.

Additionally, the at least some of the aragonite particles may be colored and/or comprise an antimicrobial agent (e.g., via coating or impregnation). Further contemplated aragonite particles comprise water or are even water saturated (particularly to control temperature). Therefore, in other embodiments the backing may have drainage holes or comprises a water permeable material.

In a second aspect of the invention, a method according to claim <NUM> is provided. The method of reducing temperature excursions of an artificial turf structure includes the steps of providing an artificial turf structure that comprises a plurality of turf fibers coupled to a backing, and at least partially filling a space between the turf fibers with a plurality of aragonite particles to thereby reduce temperature excursions as compared to the artificial turf structure with a silica filler. For example, such methods may reduce the temperature excursion by at least <NUM>, or at least <NUM> ( <NUM>, or at least <NUM> °F).

For reduced compaction, in some embodiments, the microporous oolitic aragonite particles may have a uniformity constant of between about <NUM> to about <NUM>. Preferably, the microporous oolitic aragonite particles have a uniformity constant of between about <NUM> to <NUM>.

It has been found that oolitic aragonite particles may also enhance water drainage as compared to the artificial turf structure with a silica filler.

In at least some embodiments, it is preferred that the aragonite particles are contacted or even saturated with water.

Various objects, features, aspects, and advantages will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing in which like numerals represent like components.

The inventors have now discovered that aragonite, and particularly oolitic aragonite will provide numerous benefits over conventional filler materials when used in ground covers. Most significantly, oolitic aragonite provided superior drainability, cooling (via reflectivity and water evaporation properties), dimensional stability in a layer (as oolitic aragonite will not significantly compact), and ammonia neutralization capabilities (which is especially desirable where pet or other animal waste is present).

While not limiting to a particular theory or hypothesis, the inventors contemplate that these and other advantages of oolitic aragonite are at least in part attributable to the unique character of aragonite. More specifically, oolitic aragonite is typically spherical and highly microporous, thus endowing exceptional drainage capabilities to the material. In addition, oolitic aragonite also has an extremely high surface area of about <NUM><NUM>/g (<NUM>,<NUM> in<NUM>/in<NUM>), which means the maximum area to promote the neutralizing of ammonia and cooling effect.

Moreover, it should be appreciated that aragonite is not only a non-toxic natural product, but is also a sustainable resource. Oolitic aragonite is generated through the chemical fixation of Carbon Dioxide (CO<NUM>) to the naturally present Calcium (Ca<NUM>+) in the ocean's water, which results in the precipitation of Calcium Carbonate (CaCO<NUM>). This process is fueled by the photosynthesis within the blooms of phytoplankton; picoplankton: specifically cyanobacteria and unicellular green algae as they drift across the warm water banks of the Bahamas. Cyanobacteria have a Carbon Dioxide Concentrating Mechanism (CCM) that raises the concentration of CO<NUM> at the site of the carboxylating enzyme ribulose bisphosphate carboxylase (RUBISCO) by up to <NUM>,<NUM> times the surrounding medium. In addition, cyanobacteria excrete organic polymeric substances to form extracellular formations. These Exopolymeric Substances (EPS) serve as a nucleation surface for mineralization, accelerating the calcium carbonate generation process. The combination of the CCM and the presence of the EPS within the surrounding medium of the warm shallow waters of the Bahamas which are already supersaturated with the element Ca<NUM>+ and carbonate anions (Ca++ concentrations are at over <NUM> millimolar) readily result in the phenomenon of "Whitings", cloudy precipitation of oolitic aragonite (CaCO<NUM>) with a unique crystal morphology. This process continually produces millions of tons per year of oolitic aragonite within the Bahamas. <FIG> is an exemplary photograph of the macroscopic appearance of oolitic aragonite, and further shows a SEM image of the crystalline morphology at high magnification.

In one exemplary contemplated use where aragonite is employed as an infill for artificial turf, oolitic aragonite is dried and screened to a consistent gradation of <NUM> mesh to +<NUM> or +<NUM> mesh. The so obtained aragonite is then combined with artificial and turf grass to provide weight, to keep the synthetic grass fibers upright, to provide cooling properties and ammonia neutralization capabilities. While oolitic aragonite is typically used as described above, the aragonite can be further processed prior to use. Among other processes, aragonite may be reduced in size (e.g., micronized an average particle size of less than <NUM>, or equal or less than <NUM> micrometer, or equal or less than <NUM> micrometer, or equal or less than <NUM> micrometer, or equal or less than <NUM> micrometer, or equal or less than <NUM> micrometer), colored with one or more dyes or pigments, coated or otherwise treated with antimicrobial agents and/or scented agents, or impregnated or coated with one or more agriculturally relevant agents or chemicals (e.g., fungicide, insecticide, herbicide, fertilizer, etc.). Still further contemplated modifications include restructuring of aragonite as is described in <CIT> (<CIT>). Likewise, the aragonite may also be reduced in size while retaining its oolitic shape, typically using a ball mill process. Thus, suitable milled aragonite may include oolitic aragonite having an average particle size of between <NUM>-<NUM> micrometer, or between <NUM>-<NUM> micrometer, or between <NUM>-<NUM> micrometer, or between <NUM>-<NUM> micrometer, or between <NUM>-<NUM> micrometer. Such micronized particles will still retain the benefits as noted herein and described in more detail below.

With respect to the cooling effect of oolitic aragonite it should be appreciated that the microporosity present in the ooids (each particle grain) will help trap water, which in turn acts like suspended water droplets with very high surface area, creating mini-natural air conditioning cooling units as wind passes over or through them. Moreover, the color of oolitic aragonite is close to white, resulting in a highly reflective surface while scattering light multi-directionally due to the crystalline morphology of the aragonite surface crystals as can be seen in <FIG>. Notably, milling oolitic aragonite will produce an even whiter product as compared to raw oolitic aragonite. Preliminary tests of milled aragonite as an infill with artificial grass have shown that the temperature of the so filled artificial grass was approximately <NUM> degrees Celsius ( <NUM> degrees Fahrenheit) cooler than standard infill based on silica sand. Typically, the temperature excursion of the ground cover made of artificial turf and microporous oolitic aragonite particles upon exposure to sun is <NUM> degrees (°C) (<NUM> degrees (F) ) cooler than artificial turf with silica sand or without infill. For example, the temperature excursion of the ground cover made of artificial turf and microporous oolitic aragonite particles is about <NUM> to <NUM> degrees (°C) cooler (<NUM> to <NUM> degrees (F)).

Notably, the total porosity of the microporous oolitic aragonite particles is desirable. Typically, aeration porosity is made up of relatively large pores that conduct water under saturated conditions. When drained, they are filled with air, providing the oxygen that is necessary for root growth. The capillary porosity is made up of small pores that hold water against the force of gravity, retaining much of it for plant use. Ideally, a root zone mix would contain a nearly equal distribution of air and water filled pore space after free drainage. In typical embodiments, the aeration porosity of the microporous oolitic aragonite particles is of between about <NUM>% to about <NUM>%. For example, the aeration porosity of the microporous oolitic particles is about <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%.

In addition, it should be noted that oolitic aragonite and micronized/milled oolitic aragonite had also a remarkable dimensional stability. Indeed, the oolitic aragonite particles and the micronized/milled oolitic aragonite particles had a uniformity coefficient (Cu) of about <NUM>, which is typically regarded a uniformly graded sand that contains particles of the same size and hence more volume of voids. Typically, the disclosed oolitic aragonite particles (e.g., micronize/milled oolitic aragonite particles) have a Cu that does not exceed <NUM>. For example, the the oolitic aragonite particles have a Cu of or between about <NUM> to about <NUM>. More typically, the oolitic aragaonite particles have a Cu that does not exceed <NUM>. For example, the oolitic aragonite particles have a Cu of or between about <NUM> to about <NUM>. Most typically, the oolitic aragonite particles have a Cu of or between about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. Preferably, the oolitic aragonite particles have a Cu of or between about <NUM> to about <NUM>. Most preferably, the oolitic aragonite particles have a Cu of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The uniformity of the oolitic aragonite particles results not only in significantly reduced compaction or even no measurable compaction, but also in very high hydraulic conductivity (water movement) through a layer formed by the aragonite. In other words, aragonite ooids are generally smooth and round in structure, unlike the angular and rough surface of silica sand. The desirable uniformity coefficient (Cu) of aragonite allows for a maximum number of particles of the same size which together with the increased volume of voids between the particles (which are substantial factors in both drainage and compaction), the disclosed oolitic aragonite does not compact under pressure like angular sands (silica). Indeed, the saturation constant (Ksat) of oolitic aragonite was measured to be at least <NUM> inches per hour (in/hr), indicating excellent drainage capabilities. Preferably, the Ksat of the oolitic aragonite particles (e.g., micronized/milled oolitic aragonite particles) is about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM> in/hr. More preferably, the Ksat of the oolitic aragonite particles is of from about <NUM> in/hr to about <NUM> in/hr. For example, the Ksat of the oolitic aragonite particles is about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> in/hr.

Moreover, the inventors discovered that oolitic aragonite also provided excellent neutralization of ammonia smell, typically due to decomposition of urea found in human, livestock, and pet urine. Urine commonly has a pH of <NUM> to <NUM> and contains urea (CO(NH<NUM>)<NUM>). Hydrolysis of urea results in the formation of ammonia and ammonium molecules, causing the undesirable urine smell. Oolitic aragonite has high levels of exchangeable calcium (Ca<NUM>+), which can offset the pH increase caused by urea hydrolysis and as such prevents or reduces the volatilization of the ammonia molecules. As such, artificial turf and lawn products with oolitic aragonite infill will not only have a higher durability and resist wrinkling and matting, but also reduce or even entirely prevent malodors due to animal urine decomposition.

Oolitic aragonite was analyzed for particle size distribution and particle shape, and exemplary results are provided in <FIG>. As can be readily seen, the material was very uniform in particle size, with most of the particles falling into the medium size fraction. The uniformity of the particle size is illustrated by the uniformity coefficient (Cu). Indeed, the aragonite material had a particle size distribution that was substantially more uniform than typical other silica based materials. Moreover, the particle shape was determined to be mostly rounded. Selected physical properties of the aragonite sample, as determined on compacted cores, are shown in <FIG>.

The total porosity was desirable in the sample. Typically, aeration porosity is made up of relatively large pores that conduct water under saturated conditions. When drained, they are filled with air, providing the oxygen that is necessary for root growth. The capillary porosity is made up of small pores that hold water against the force of gravity, retaining much of it for plant use. Ideally, a root zone mix would contain a nearly equal distribution of air and water filled pore space after free drainage.

The inventors performed a water release curve on the sand sample. In a sand or sand based mix profile, the deeper the profile depth the greater the aeration porosity will be because of a greater hydraulic head or pressure. The inventors applied increasing levels of energy to the sample to extract water from it, simulating varying depths of sand. By doing this, the inventors can identify a minimum plating depth that will provide desirable physical properties. The inventors identified this minimum depth by the point (depth) at which the inventors obtained a minimum aeration porosity of <NUM>% by volume with an optimum being the point where the aeration and capillary porosity curves intersect. The graph in <FIG> shows the aeration and capillary porosity values at different simulated depths. As can be clearly seen, the sample had an aeration porosity of <NUM>% at a depth of about <NUM> inches (<NUM>,<NUM>) with an optimum depth of <NUM> inches (<NUM>,<NUM>). Plating the sand at a depth less than the minimum would run the risk of the sand retaining too much water at the expense of air.

Claim 1:
An artificial turf ground cover, comprising:
a plurality of artificial turf fibers coupled to a backing to form an artificial turf structure; and an infill disposed between the artificial turf fibers
characterized in that
the infill is made of microporous oolitic aragonite particles having a surface that scatters light in multiple directions.