ARTIFICIAL TURF INFILL WITH PU-COATED WALNUT SHELL GRANULATE

Abstract

 The invention relates to artificial turf infill (602). The artificial turf infill comprises walnut shell granulate having one or more PU coatings

Description

Field of the invention

[0001] The invention relates to artificial turf and methods for the manufacture of artificial turf infill.

Background and related art

[0002] Artificial turf or artificial grass is surface that is made up of fibers which is used to replace grass. The structure of the artificial turf is designed such that the artificial turf has an appearance which resembles grass. Typically artificial turf is used as a surface for sports such as soccer, American football, rugby, tennis, golf, for playing fields, or exercise fields. Furthermore artificial turf is frequently used for landscaping applications. Hybrid grass or reinforced natural grass is a product created by combining natural grass with synthetic reinforcing fibres. It is used for stadium pitches and training pitches, used for association football, rugby, American football, golf and baseball. Reinforced natural grass can also be used for events and concerts. The synthetic fibres incorporated into the rootzone make the grass stronger and more resistant to damage. A first generation of hybrid grass allowed grass roots to intertwine with a mix of sand and synthetic fibres as they grew. Synthetic fibres are integrated in the root zone e.g. by mixing fibres and sand in an automated plant and to install it afterwards on the pitch ("Fibresand") or by putting a mat with woven or tufted fibres on the surface, to brush in sand or sand mixes afterwards to keep the fibres in an upright position and to seed grass mixtures finally. The natural grass roots through the mat and stabilizes the system. Hybrid grass as used herein is considered as a special type of artificial turf.

[0003] Artificial turf may be manufactured using techniques for manufacturing carpets. For example artificial turf fibers which have the appearance of grass blades may be tufted or attached to a backing. Often times artificial turf infill is placed between the artificial turf fibers. Artificial turf infill is a granular material that covers the bottom portion of the artificial turf fibers. The use of artificial turf infill may have a number of advantages. For example, artificial turf infill may help the artificial turf fibers stand up straight. Artificial turf infill may also absorb impact from walking or running and provide an experience similar to being on real turf. The artificial turf infill may also help to keep the artificial turf carpet flat and in place by weighting it down.

[0004] European patent application EP 1 416 009 B1 describes a loose, free flowing rubber particles as litter material for artificial turf. The particles have an average size between 0.4 mm and 4.0 mm and their complete surface is covered with a permanently elastic and pigmenting coating.

[0005] European patent application EP1201388 B1 discloses a method of manufacturing colored rubber chips.

[0006] International patent application WO 2010/081632 A1 discloses a method for producing coated particles made of rubber granulate, the coating, the particles coated with said coating, and the uses of the coated particles. The coating contains no solvents.

[0007] European patent application EP3216821A1 describes a method manufacturing artificial turf infill. The method comprises mixing a granulate, one or more pigments and a fluid binding agent for providing an initial coating of the granulate. Then, a subsequent composition comprising the granulate with the initial coating, one or more pigments and the fluid binding agent is mixed for providing a subsequent coating of the granulate.

[0008] International patent application WO 2018/016956 A2 describes an artificial turf with a granular, coated infill. The granular infill may comprise cork or coconut.

Summary

[0009] The invention provides for a method of manufacturing artificial turf infill, artificial turf comprising the same, and artificial turf infill. Embodiments are given in the dependent claims. Embodiments and examples described herein can freely be combined if they are not mutually exclusive.

[0010] In one aspect, the invention relates to artificial turf infill. The artificial turf infill comprises walnut shell granulate having one or more polyurethane (PU) coatings.

[0011] A walnut shell granulate based, PU coated infill may be beneficial because it may provide for a new type of artificial turf infill that is compression resistant, rigid and that is dimensionally more stable during manufacturing and use than, for example, coconut shells.

[0012] In a further beneficial aspect, the PU coating provides elasticity to the infill and hence improves the mechanical properties of the artificial turf infill layer.

[0013] In a further beneficial aspect, the PU coating reduces dust formation during the manufacturing process of the infill granulate. Walnut shells tend to break into many tiny pieces that are easily blown away if used as infill without further processing. By applying a PU coating, the size and weight of the walnut shell granules, in particular the small granules, is increased and the loss of infill material due to wind and rain is reduced.

[0014] Moreover, walnut shell granulate can be manufactured more easily, because walnut shells are much thinner and hence easier to grind than coconut shells. Walnut shells are cheap as the shells are a by-product and waste-product of the food industry.

[0015] In a further beneficial aspect, applicant has observed that the PU coating effectively protects the players from allergens that may be contained in the walnut shells.

[0016] According to some embodiments, the walnut shells are not heated to a temperature of more than 60°C before being coated with the PU coating.

[0017] In a further beneficial aspect, using a PU coating may allow adding pigments to the PU coating and hence to provide a bio-based infill having a desired, freely selectable color.

[0018] Applicant has observed that some people have allergies against some natural products, e.g. coconut shells. One possibility to prevent an allergic reaction of some of the players to a nut-based infill is to heat the nut granules or the coated infill to temperatures of more than 60°C or higher in order to ensure that the allergens - typically proteins - are heat-denaturized and lose their allergenic properties. Applicant has observed that the PU coating may likewise protect the players from any allergens that may be contained in the walnut shell granules. Hence, there is no need to heat the walnut shells. This may reduce energy consumption during the production process of the coated walnut shells and hence reduce production costs.

[0019] According to some embodiments, the walnut shells are not irradiated by radioactive beta- or gamma-rays before being coated with the PU coating. The irradiation is sometimes used for preventing a biodegradation of organic infill material.

[0020] Applicant has observed that the PU coating may likewise protect the walnut-shell based infill from biodegradation. Hence, there is no need to irradiate the walnut shells or walnut shell granules. This may reduce energy consumption during the production process of the coated walnut shells and hence reduce production costs.

[0021] In a further beneficial aspect, applicant has observed that walnut shell granulate is significantly less prone to biodegradation than coconut shells and other bio-based infill types. This is because walnut shells do basically not absorb any water. Coconut shells and other types of organic infill are porous and hence may absorb water. The absorbed water results in a continued (bio)degradation of the coconut shell material. In order to prevent biodegradation, organic infill particles are therefore often combined with antimicrobial substances. However, antimicrobial substances may increase the price of the infill and may be undesirable, e.g. when the infill is used as infill for hybrid turf. Hence, the use of walnut shells may provide for a new type of organic infill that is robust against biodegradation even in the absence of antimicrobial substances.

[0022] In a further beneficial aspect, that walnut shells do basically not absorb any water or absorb only very small amounts of water. This feature may provide for a remarkable dimensional stability of walnut shell granulate even in case the walnut shell granulate is repeatedly subjected to cycles of rainfall and draught. Dimensional stability is an important feature of a substance used as infill: if the dimensional stability of the infill is lost, there is a risk that the infill forms a water-impermeable, continuous layer that prevents any gas and water exchange between the upper and the lower side of an artificial turf. As a consequence, rain water may build puddles and organic material in the soil below the artificial turf may start to mold. Coconut shells and other types of organic infill are porous, absorb water and may swell or otherwise change their shape if contacted with water and/or if repeatedly subjected to mechanical forces. In particular, frequent changes between water absorption (swelling) and desorbtion (drying) may reduce the dimensional stability of coconut granulate and other types of water-absorbent infill particles. In some cases, coconut shell based granules are therefore kept moist constantly in order to avoid frequent swelling/drying cycles and to ensure dimensional stability of the infill which has the disadvantage of accelerated biodegradation.

[0023] The elastic PU coating may increase the robustness of the infill granulate against abrasion and against damages induced by multiple freeze-thaw-cycles: if inelastic infill material is pressed by water that expands its volume in a freezing process against other, inelastic infill material, the infill material will be damaged. An elastic coating protects the infill granules from this effect.

[0024] Walnut shell granulate has been surprisingly observed to provide the advantage of being more robust against biodegradation and at the same time having a greater dimensional stability than coconut based granulate.

[0025] In a further beneficial aspect, walnut shell granulate has an ochre (yellow-brownish) color that looks like the color of natural sand. Hence, the walnut granulates may be used alone or in combination with sand for providing an artificial turf that faithfully reproduces natural grass comprising sand. This may reduce costs, because no ochre pigments are needed for generating a sand-like color. Furthermore, it is in generally considered difficult to faithfully reproduce a particular, natural color such as sand, because often sand has many different shades and may comprise smaller stones of different colors and this heterogeneity is difficult to reproduce using a defined set of chemical pigments. By using walnut shell granules, the natural color of sand can be easily reproduced without having to introduce complex steps in the manufacturing workflow for obtaining infill with a defined, reproducible heterogeneity of ochre colors.

[0026] In a further beneficial aspect, the comparatively bright color of walnut shell granules whose PU coating is free of any pigments has been observed to reflect a significant portion of the sunlight, thereby preventing a heating of the artificial turf that is observed for other types of infill, e.g. black SBR rubber made of shredded car tires.

[0027] In a further beneficial aspect, walnut shell based infill is compostable and hence environmentally friendly.

[0028] According to embodiments, at least one of the one or more coatings is completely closed and free of gaps. This may be advantageous because the absorption of water by the walnut shells is completely prevented, thereby increasing dimensional stability and robustness against biodegradation.

[0029] According to embodiments, each of the one or more coatings comprises gaps. The gaps of the one or more coatings allow water to penetrate the one or more coatings and reach the walnut shell granulates.

[0030] The gaps in the first and second coatings may be distributed randomly on the surface of the granulate. As the gaps in both coatings are distributed randomly, it is unlikely that the gaps will line up. The result will be that there will be few if any portions of the underlying granulate exposed. It is possible that some of the gaps in the first and second coatings may line up. However, all or the vast majority of the surface of the granulate will be coated. Using the double coating may greatly reduce the amount of fluid PU reaction mixture necessary to coat the granulate.

[0031] According to embodiments, each of the one or more coatings is free of a pigment. This may be advantageous as costs are reduced. Thin PU layers are transparent and the natural color of the walnut shell granulate may already have the desired color, i.e., the color of sand.

[0032] According to embodiments, the walnut shell granulate comprises at least two coatings. For example, the walnut shell granulate may comprise two, three, four or even five coatings.

[0033] This may be beneficial because it may provide for better coating of the granulate For example, during the mixing of an initial composition comprising the walnut shell granulate and a PU reaction mixture, individual grains of the walnut shell granulate will touch and interact with each other as the initial coating on each of the grains forms. The physical contact between different grains will however cause defects. By coating the granulate particles a second time with the subsequent coating, much higher coverage of the granulate can be achieved. Hence, the elasticity of the coated walnut shell granulate and the robustness of the granulate against abrasion and against damages induced by multiple freeze-thaw-cycles may be increased.

[0034] As a hypothetical example, during the formation of the first coating or the second coating the coverage is each only 90% of the surface of the granulate. After the first coating has been deposited, roughly 10% of the surface of each granule of the granulate would be uncoated. There would be small surface defects. Deposition of the subsequent coating would then also cover 90% of the surface. As the interaction between the grains or particles of the granulate is essentially a random process, one can expect that 90% of the defects that were exposed after the deposition of the initial coating are coated in this case. The result of doing two coatings is then an artificial turf infill that is 99% coated with only minor amounts of defects, where the granulate is not coated with either the first coating or the second coating.

[0035] Improving the coverage of the granulate may be beneficial in several different situations. For example, it may be desirable to color the artificial turf infill the same or a similar color as fibers or tufts, which are used to manufacture an artificial turf carpet. This may provide a more realistic-looking play surface or playfield.

[0036] The one or more pigments in the first coating, if any, may be identical or they may be different from the one or more pigments in the second coating, if any. If they are the same then the coating of the granulate will be of a uniform color. If the at least one second type of pigment and the at least one first type of pigments are different colors then the two colors can be chosen so that the resulting artificial turf infill has a more natural, "speckled" and earth like appearance.

[0037] Another advantage of multiple layers of coating is that the elastomeric granulate may be better coated and may therefore have superior wear qualities or may even be better isolated from the environment.

[0038] For example, the pigment in the first and/or second coating can be one of the following: iron oxide, iron oxide hydroxide, chromium(III) oxide, a copper phythalocyanine pigment, a nickel azopigment, titanium oxide and combinations thereof.

[0039] In some embodiments, the second coating at least partially covers the first, initial coating. In some embodiment the first coating only partially covers the walnut shell granulate. In another embodiment the second, subsequent coating only partially covers the first coating.

[0040] According to embodiments, at least one of the one or more coatings comprises one or more types of pigment, preferably bright pigments, e.g. white, yellow or ochre pigments.

[0041] According to embodiments, at least one of the one or more coatings comprises one or more types of pigment.

[0042] According to embodiments, the walnut shell granulate without the two or more coatings has an average diameter between 0.1 mm and 4.0 mm, preferably between 0.4 mm and 3.0 mm. In another embodiment the granulate has an average diameter between 0.45 mm and 2.0 mm.

[0043] According to embodiments, the walnut shell granulate without the two or more coatings has a maximum diameter less than 5.0 mm. In another embodiment the granulate has a maximum diameter of less than 4 mm.

[0044] In another embodiment, the first coating and the second coating each have a coating layer thickness of 0.6 µm to 40µm, preferably 1 µm to 30 µm.

[0045] According to embodiments, the walnut shell granulates are coated with a single PU layer. The single PU layer is applied such that about 1 %-7%, preferably 2%-5%, e.g. about 4% of the mass of the walnut shell granule consists of the PU coating. For example, a PU mass of about 4% by weight of an (uncoated) walnut shell granule is used for coating a walnut shell granule. Single coated walnut shell granules have a comparatively large number of gaps in the PU coating. Hence, water can be easily and quickly adsorbed and desorbed via the single PU coating layer. This type of infill may be particularly advantageous when used in hot and dry climate zones where the evaporation-based cooling effect significantly improves the mechanical properties of the turf.

[0046] According to other embodiments, the walnut shell granules are coated with two PU layers. Each of the two PU layers is applied such that the amount of this particular layer is about 1 %-7%, preferably 2%-5%, e.g. about 4% of the mass of an uncoated walnut shell granule. For example, about 4% by weight of the uncoated granulate correspond to the first, inner PU coating. About 4% by weight of the uncoated granulate correspond to the second, outer PU coating. Walnut shell infill granules with two or even more PU coatings may have a smaller number and size of gaps than single-coated granulates and hence may reduce the speed of water adsorption and desorption. However, the elasticity and robustness of walnut shell granules with two or more layers is significantly increased. Hence, multi-fold PU coated walnut shell infill granules may be particularly beneficial when used in cold climate zones and/or for sports fields which are subject to high mechanical stress.

[0047] According to embodiments, the one or more PU coatings are elastic.

[0048] According to embodiments, the walnut shell granulates are coated with at least two PU layers. This may be particularly advantageous, as the risk that any allergen that may be contained in the walnut shell granulate can leave the infill granulate is significantly reduced. If only a single PU layer is applied, there may remain in some cases some small regions on the surface of the walnut shell granule surface which is not covered by the PU coating. Providing two or even more layers of the PU coating may provide for an efficient protection against any substances leaving or entering the walnut shell granule through the coating layer(s).

[0049] According to embodiments, each of the one or more PU coatings is free of antimicrobial substances such as, for example, antibacterial agents like silver or chitosan.

[0050] According to embodiments, the artificial turf infill further comprises sand and/or rubber granulate. For example, the rubber can be a synthetic rubber as e.g. styrene butadiene rubber, polybutadiene rubber, styrene- ethylene-butadiene-styrene copolymer (SEBS), ethylene-propylene-diene monomer rubber (EPDM), acryl nitrile butadiene rubber. In other embodiments a cis- 1,4 -polyisoprene, as natural rubber and trans 1,4 -polyisoprene as gutta-percha based granulate can be used.

[0051] According to embodiments, each of the one or more PU coatings is free of a pigment. The artificial turf infill further comprises sand. This may be advantageous as all grains of the sand-PU-coated walnut shell granulate mixture basically look like sand without imposing additional costs and effort related to the adding of additional pigments having a sand-like color.

[0052] According to embodiments, each of the one or more PU coatings is free of a pigment. The artificial turf infill further comprises sand and/or a PU-coated rubber granulate, whereby the coating of the rubber granulate comprises one or more ochre colored pigments. This may be advantageous as all grains of the sand/rubber/-PU-coated walnut shell granulate mixture basically look like sand without imposing additional costs and effort related to the adding of additional pigments having a sand-like color.

[0053] In a further aspect, the invention relates to an artificial turf. The artificial turf comprises an artificial turf carpet. The artificial turf carpet comprises multiple artificial turf fiber tufts and artificial turf infill according to any one of the embodiments and examples described herein. The artificial turf infill is spread between the multiple artificial fiber tufts.

[0054] In a further aspect, the invention relates to a method manufacturing artificial turf infill. The method comprises:

• providing an initial composition comprising a walnut shell granulate and a fluid PU reaction mixture;
• mixing the initial composition;
• adding water and a catalyst to the initial composition during the mixing of the initial composition to cure the fluid PU reaction mixture into a first PU coating of the walnut shell granulate; and
• providing the PU coated walnut shell granulate as the artificial turf infill.

[0055] Said features may be advantageous, because the water is added after the mixing has already started and during the mixing. This may ensure that the reaction that creates the PU has not completed when the granules get in contact with the reaction mixture. Rather, the reaction mixture may already wet the granules when the water is added and the reaction starts. This may ensure that the PU reaction mixture and the PU coating created therefrom strongly adheres to the walnut shell granules.

[0056] According to embodiments, the method further comprises:

• providing a subsequent composition comprising the walnut shell granulate with the first PU coating, and a further fluid PU reaction mixture;
• mixing the subsequent composition;
• adding water and the catalyst to the subsequent composition during the mixing of the subsequent composition to cure the fluid binding agent a second PU coating of the walnut shell granulate; and
• providing the PU coated walnut shell granulate with the first and second coating as the artificial turf infill.

[0057] Optionally, one or more further coatings can be applied, e.g. by generating a further, subsequent composition by adding at least one additive and the PU reaction mixture to the walnut shell granulate that has already been coated with the one or more previously applied coatings. The next step in the sequence is to mix the further subsequent composition, add water and the catalyst to the further subsequent composition during the mixing of the further subsequent composition to cure the fluid PU reaction mixture into a further coating. The granulate with the further coating is provided then as the artificial turf infill. The generation of multi-layer coatings may be beneficial because an additional coating or layer may be put on the granulate, thereby increasing elasticity and the shock absorbing capabilities of the infill layer. If the multiple coatings comprise the same pigment(s), then the coverage of the color may be improved. This embodiment may also be beneficial because it may enable the deposition of so-called functional layers or additives, which may add to the utility or wear or usefulness of the artificial turf infill.

[0058] The curing of the first and/or second coating can be a polymerization process.

[0059] According to embodiments, the initial and/or the subsequent composition is free of a pigment. The method further comprises mixing the PU coated walnut shell granulate with sand and/or with a PU-coated rubber granulate for providing a multi-component infill mixture. The coating of the rubber granulate comprises one or more ochre colored pigments. The method further comprises using the multi-component infill mixture as the artificial turf infill.

[0060] According to embodiments, the initial and/or the subsequent composition respectively comprises one or more additives. The additive are selected from a group comprising: a first type of pigment, a second type of pigment, a flame retardant, a zeolite, an IR reflective pigment, a hindered amine light stabilizer, an anti-freeze additive, a de-icing additive, sodium chloride, potassium chloride, sodium formiate, potassium formiate, and combinations thereof.

[0061] The flame retardant can be, for example, aluminum trihydrate, magnesium hydroxide turning a by itself burnable or flammable elastomeric material into a flame retardant infill material. In one embodiment this flame retardant additives creates an intumescent coating and is based on intumescent component comprising ammonium polyphosphate or exfoliated graphite or a mixture hereof.

[0062] The hindered amine light stabilizer (HALS) is able to protect the PU coating as well as the walnut shell granulate against UV degradation.

[0063] The thermostabilizing agent protecting the walnut shell granulate and the PU coating against thermal degradation.

[0064] The anti-freeze/ deicing additive can be, for example, a substance selected from the group comprising: sodium chloride, potassium chloride, calcium chloride, sodium formiate, potassium formiate or a mixture hereof. The additive is migrating into the neighborhood of the granulate and by this inhibits the formation of ice by freezing humidity between the infill granulate particles.

[0065] The addition of zeolite may be beneficial because the ability of the surface of the artificial turf infill to absorb or de-absorb water may be increased. For example before a football game, which is scheduled to be held in the sun or in hot conditions, water may be sprayed onto the artificial turf and the zeolite may absorb an amount of water. As the sun or hot air heats the artificial turf infill during the game, the evaporation of water may cool the playing surface for the players and make the use of the artificial turf more pleasant. In another embodiment the at least one additive further comprises methylcellulose, which may be beneficial in a similar way like zeolite for absorbing and desorbing of water, rendering a cooling effect at hot climatic conditions. The use of the IR reflective pigments as mixed metal oxides may be beneficial because it may reflect infrared light. This may reduce the heating of the artificial turf infill. A specific advantage may be that in this case the comparably expensive and precious pigments are merely on the surface of the infill granulates, where they are fully effective and not in the complete core of the infill granulate.

[0066] According to embodiments, the catalyst contained in the initial and/or the subsequent composition is partially or completely water soluble and is of the group: secondary amine, tertiary amine, a metal organo cytalyst.

[0067] According to embodiments, the initial and/or the subsequent composition comprises an NCO terminal polymer which might be a pre-polymer, a polymeric isocyanate, an oligomeric isocyanate, a monomer and a mixture hereof. The NCO terminal polymer can be an aromatic diisocyanate of the group toluene diisocyanate or methylene-2,2 -diisocyanate. In another embodiment the NCO terminal polymer can be an aliphatic diisocyanate of the group hexamethylene diisocyanate, isophorone diisocyanate and 1,4-cyclohexyldisiocyanate.

[0068] In a preferred embodiment the initial and/or the subsequent composition comprises a methylenediphenyl-isocyanate isomer mixture. In another embodiment the hydroxyl component of the PU reaction mixture is out of the group polyether polyol or polyester polyol. For example, the hydroxyl component is based on a polyetherpolyol of the molecular weight 500 to 10000. In a preferred embodiment the polyetherpolyol has a molecular weight of 1500- 6000. In a very preferred embodiment the molecular weight is in the range of 2000- 4000.

[0069] According to embodiments, the initial and/or the subsequent composition respectively comprises one or more additional types of granulate. The additional type of granulate is selected from a group comprising rubber, an elastomeric polymer, Metallocene Butadiene Rubber, nitrile rubber granulate, natural rubber granulate, styrene-butadiene rubber granulate, ethylene propylene diene monomer rubber granulate, black crumb rubber granulate, acrylonitrile butadiene rubber, a thermoplastic polymer, Styrene Ethylene Butylene Styrene , Styrene Block Copolymers, an elastic foam, elastic polyurethane (PU) foam, and combinations thereof.

[0070] According to embodiments, the method further comprises grinding walnut shells in a mill for providing the walnut shell granulate.

[0071] According to embodiments, the PU reaction mixture of the initial and/or of the subsequent composition comprises one or more MDI monomers, a partially polymerized polymer, an isocyanate and a catalyst.

[0072] In a further aspect, the invention relates to a method of manufacturing artificial turf. The method further comprises installing an artificial turf carpet at a use site, wherein the artificial turf carpet comprises multiple artificial turf fiber tufts; and providing the artificial turf by spreading a layer of artificial turf infill as described herein for embodiments and examples of the invention between the multiple artificial turf fiber tufts.

[0073] Artificial turf infill may be used to modify an artificial turf carpet to have more earth like properties. For example the artificial turf infill may provide a surface which is able to absorb impacts in a manner similar to real turf.

[0074] According to embodiments, the PU reaction mixture(s) us (are) cured into at least one type of polyurethane by water and the catalyst.

[0075] According to embodiments, the liquid PU reaction mixture of the initial and/or subsequent composition comprises an NCO terminal polymer, which may comprise a pre-polymer, an isocyanate, a monomer, and a mixture thereof.

[0076] According to embodiments, the liquid PU reaction mixture of the initial and/or subsequent composition comprises an aromatic diisocyanate of the group of toluene diisocyanate and/or methylene- 2,2 -diisocyanate. The liquid PU reaction mixture can comprise an aliphatic diisocyanate of the group hexamethylene diisocyanate, isophorone diisocyanate, and/or 1,4-cyclohexyldisiocyanate. The liquid polyurethane PU reaction mixture can comprise an methylenediphenyl-isocyanate isomer (MDI) mixture, in particular, a 2,2', 2,4' and a 4,2' MDI mixture.

[0077] According to embodiments, the liquid PU reaction mixture comprises a hydroxyl component (also referred to as "polyol component"). The hydroxyl component is selected from the group of polyether polyol or polyester polyol. According to some examples, the hydroxyl component is based on a polyetherpolyol with a molecular weight between 500 and 10000, preferably the molecular weight is between 1500 and 6000, and more preferably the molecular weight is between 2000 and 4000.The PU reaction mixture preferably comprises a catalyst that belongs to any one of the following groups: a secondary amine catalyst, a tertiary amine catalyst, and a metal organic catalyst.

[0078] Preferably, the first coating is allowed to cure before the second coating is applied.

[0079] It may also be possible to dry the initial composition after coating the granulate with the first coating; however, it is not necessary. The water, which is leftover from the formation of the first coating on the elastic and /or compression resilient granulate may be used in the reaction of the subsequent composition. The second coating is made from the subsequent composition, if any, and is preferably cured and dried before the granulate is provided as the artificial turf infill.

[0080] According to embodiments, the method is at least partially performed in a flow reactor. In the flow reactor the walnut shell granulate is slowly moved along a linear sequential path, where the granulates are generally mixed and moved along. The benefit of using a flow reactor is that the artificial turf infill may be produced on a continuous basis.

[0081] In another embodiment the method is at least partially performed as a batch process. The initial coating is formed on the walnut shell granulate during an initial batch and the subsequent coating is formed on the granulate during a subsequent batch. Forming the initial coating and the subsequent coating in separate batches may be beneficial because it may enable precise control over the formation of the initial and subsequent coatings.

[0082] According to embodiments, the method is at least partially performed as a batch process. The initial coating is formed on the granulate during an initial batch. The subsequent coating is formed on the granulate during a subsequent batch.

[0083] According to embodiments, the initial coating and the subsequent coating each have a coating layer thickness of 0.6 µm to 40µm, preferably 1 µm to 30 µm, e.g. about 15µm to 25 µm.

[0084] According to embodiments, the first and/or second PU coating is a cured, elastic PU foam layer.

[0085] According to embodiments, the artificial turf fiber tufts are arranged in rows. The artificial turf fibers have a row of space in between 0.5 cm and 1.95 cm. This corresponds approximately to 3/8" to 3/4". In some examples, the artificial turf covering has a pile height between 2.5 cm and 7.5 cm. The pile height is the length of the artificial turf fibers above the backing or base of the artificial turf carpet.

[0086] It is understood that one or more of the aforementioned embodiments of the invention may be combined as long as the combined embodiments are not mutually exclusive.

Brief description of the drawings

[0087] In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

Fig. 1

illustrates a cross sectional view of an uncoated grain of a walnut shell granulate;

Fig. 2

illustrates the granule of Fig. 1 after being partially coated with an initial coating;

Fig. 3

illustrates the granule of Fig. 2 after being partially coated with a subsequent coating;

Fig. 4

illustrates the granule of Fig. 3 after being partially coated with a subsequent coating;

Fig. 5

illustrates an example of an artificial turf carpet;

Fig. 6

illustrates an example of artificial turf;

Fig. 7

shows a flow chart which illustrates a method of manufacturing artificial turf infill;

Fig. 8

shows a flow chart which illustrates a further method of manufacturing artificial turf infill;

Fig. 9

shows a flow chart which illustrates a method of manufacturing artificial turf;

Fig. 10

illustrates an example of a batch reactor;

Fig. 11

illustrates an example of a flow reactor; and

Fig. 12

is a photo of a walnut shell granulate covered by a brownish PU coating.

Detailed Description

[0088] Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent.

[0089] Figs. 1-4 illustrate the manufacture of artificial turf infill by examining a single walnut shell grain or granule 100. The granule 100 could for example be made by grinding walnut shells in a mill. For example, the granule 100 can be generated by a nuts grinding machine comprising an electrical motor that drives a main shaft to rotate at a high speed and that spins off the material into the grinder. The walnut shells can be ground between a moving plate and the fixed plate by striking, shearing and/or grinding. The ground material can be carried by air flow through to a collecting bag. The size of the particle can be adjusted by using screens with different screen holes.

[0090] Fig. 1 shows a single, not yet coated walnut shell grain or granule. The view shown in Figs. 1-4 is a cross-sectional view.

[0091] Fig. 2 shows the same grain 100 or granule after it has been coated with a first PU coating 200. The first coating 200, also referred to as "initial coating", was formed by providing an initial composition of a granulate, which is made up of a large number of walnut shell grains or granules 100. In general, a "granulate" refers to a plurality of granules, whereby a "granule" refers to a single grain or particle. The initial composition comprises at least a fluid PU reaction mixture used as fluid binding agent and comprises optionally one or more additives like pigments, flame retardants, etc.. The fluid PU reaction mixture comprises an isocyanate component and a polyol component. The initial composition was then mixed with the walnut shell granulate. Next, water and a catalyst were added to the initial composition during the mixing process to cure the fluid PU reaction mixture and the additives, if any, into the initial PU coating 200. As a large number of these granules 100 or grains are mixed, they interact with each other and bump into each other occasionally during the process. For this reason there may be holes or defects in the initial coating 200. In Fig. 2 it can be seen that there are a number of gaps 202 in the initial PU coating 200. These are regions where the grain 100 or granule is coated or is insufficiently coated by the initial coating 200.

[0092] Fig. 3 shows the same grain 100 or granule after it has been coated with a second ("subsequent") coating 300. As with the first ("initial") coating 200 the subsequent PU coating 300 does not completely cover all portions of the walnut shell grain 100 or granule. However, due to the two-step process almost the entire grain 100 or granule 100 is coated. In this example there can only be seen one gap 202. The subsequent coating 300 was formed by providing a subsequent composition comprising the granulate with the initial coating as is shown in Fig. 2 and then combining it with a further fluid PU reaction mixture to provide a subsequent PU reaction mixture ("subsequent composition"). This subsequent composition was then mixed. During the mixing process additional water and a catalyst were added to the subsequent composition to cure the fluid PU reaction mixture into the second PU coating 300.

[0093] Fig. 3 illustrates how a two-step coating process may be used to improve the coverage or quality of the coating on a granule that makes up a larger granulate. Granules manufactured, such as is shown in Fig. 3, may be provided as a group to form an artificial turf infill. It is also possible to perform further coatings on the grain 100 or granule 100.

[0094] Fig. 4 shows the walnut shell grain 100 after a further PU coating 400 has been applied. This further coating 400 may for example be formed by recoating the granulate, which comprises the grain 100, by adding at least one additive and the fluid binding agent to the granulate. Next, a combination of the granulate and the the fluid PU reaction mixture form a subsequent composition. This subsequent composition is then mixed and again, water and a catalyst can be added to cure the fluid PU reaction mixture into the further coating 400. It can be seen now that the coverage of the grain 100 or granule is sufficient that there are no longer any gaps visible in this cross-section. Each of the PU reaction mixtures used for generating a respective PU coating can comprise one or more additives. The additives may be added to form a functional further coating 400. For example a flame retardant such as polyurethane aliphatic isocyanates could be added. To provide for the absorption and de-absorption of water, to cool the carpet a zeolite could be added. Also various UV-reflecting agents could be added too. In other examples an infrared reflection agent such as EPDM may be used to reduce the amount of heat absorbed by the artificial turf infill and/or also to help protect it from sunlight.

[0095] Figs. 5 and 6 illustrate the manufacture of an artificial turf using an artificial turf carpet and artificial turf infill. In Fig. 5 an artificial turf carpet 500 can be seen. The artificial turf carpet 500 comprises a backing 502. The artificial turf carpet 500 shown in Fig. 5 is a tufted artificial turf carpet in this example. The artificial turf carpet is formed by artificial turf fiber tufts 504 that are tufted into the backing 502. The artificial turf fiber tufts 504 are tufted in rows. There is row spacing 506 between adjacent rows of tufts. The artificial turf fiber tufts 504 also extent a distance above the backing 502. The distance that the fibers 504 extend above the backing 502 is the pile height 508. In Fig. 5 it can be seen that the artificial turf carpet 500 has been installed by placing or attaching it to the ground 510 or a floor. To manufacture the artificial turf the artificial turf infill made up of grains or granules such as is shown in Figs. 3 or 4 are spread out on the surface and distributed between the artificial turf fiber tufts 504. Fig. 6 shows the artificial turf carpet 500 after the artificial turf infill 602 has been spread out and distributed between the artificial turf fiber tufts 504. It can be seen that the artificial turf infill 602 is a granulate made up of individual grains 100 or granules such as is depicted in Figs. 3 or 4.

[0096] Fig. 7 shows a flowchart which illustrates a method of manufacturing artificial turf infill 602 such as is depicted in Figs. 1-3 in the coating of the single walnut shell grain 100 or granule. First in step 700 an initial composition is provided. The initial composition comprises a granulate, at least one first type of pigment, and a fluid binding agent. The fluid binding agent comprises at least one type of polymer component. Next in step 702 the initial composition is mixed. Next in step 704 during the mixing water and catalyst are added to the initial composition to cure the fluid PU reaction mixture used as fluid binding agent into an initial PU coating 200 of the walnut shell granulate. In step 706 a subsequent composition is provided. The subsequent composition comprises the walnut shell granulate with the initial coating 200 and the PU reaction mixture used as the fluid binding agent. Next in step 708 the subsequent composition is mixed. Next in step 710 water and the catalyst are added to the subsequent composition during the mixing of the subsequent composition to cure the fluid binding agent into a subsequent PU coating 300 of the granulate. Finally in step 712 the walnut shell granulate with the subsequent PU coating 300 is provided as the artificial turf infill 602. This step may optionally comprise mixing the coated walnut shell granulate with sand and/or PU coated or un-coated elastic particles, e.g. rubber granulate.

[0097] Fig. 8 shows a flowchart, which illustrates an alternate method of manufacturing artificial turf infill. The method depicted in Fig. 8 is similar to the method depicted in Fig. 7 with several additional steps. The method in Fig. 8 is identical to Fig. 7 in steps 700-710. After step 710 has been performed, step 800 is performed. Steps 802 and then 804 are performed before step 712 is performed. Steps 800, 802 and 804 are the steps of recoating the granulate after it has been coated with the subsequent PU coating. First in step 800 a subsequent composition is provided by adding at least one additive and a fluid binding agent to the granulate. Next in step 802, the subsequent composition is mixed. Finally, in step 804, during the mixing in step 802, water and catalyst are added to the subsequent composition during mixing of the subsequent composition to cure the fluid binding agent and at least one additive into the further coating 400. Finally, in step 712, the granulate that has been coated with the initial coating, the subsequent coating, and the further coating 400, is provided as the artificial turf infill 602.

[0098] Fig. 9 shows a flowchart, which illustrates a method of manufacturing artificial turf 600 such as depicted in Fig. 6. First in step 900 an artificial turf carpet 500 is installed. The artificial turf carpet comprises multiple artificial turf fiber tufts 504. Next in step 902, the artificial turf 600 is provided by spreading a layer of artificial turf infill 602 between the multiple artificial turf fiber tufts 504. The artificial turf infill comprises the granulate. The granulate comprises one or more PU coatings 200, 300, 400. Each of the one or more coatings 200, 300, 400 can comprise additives, e.g. one or more different types of pigments or flame retardants, and the PU binding agent. The pigments in each of the coatings, if any, may be identical or different.

[0099] Fig. 10 illustrates some equipment which may be used for manufacturing the artificial turf infill 602 and for coating walnut shell grain or granules 100, such as is illustrated in Figs. 1-4. Fig. 10 depicts a mixing vat 1000. The mixing vat has a rotatable shaft 1002 that is connected to a number of mixing paddles 1004. The mixing vat 1000 is filled with the walnut shell granulate 1006. The granulate can then be manufactured into artificial turf infill by following the methods illustrated in Figs. 7 or 8. Since water is added with the catalyst for forming each of the initial coating 200, the subsequent coating 300 or the further coating 400 it is not necessary to dry the granulate 1006 between the coating of each of the coatings. The granulate 1006 can be added to the mixing vat 1000 and then at different times the different materials can be added while the rotatable shaft 1002 is turned.

[0100] The apparatus depicted in Fig. 10 may be used for manufacturing the artificial turf infill as batches. It is also possible to manufacture the artificial turf infill as a continuous process using a flow reactor.

[0101] Fig. 11 illustrates an example of a flow reactor 1100. The example shown in Fig. 11 is illustrative and is not drawn to scale. The flow reactor 1100 comprises a rotatable shaft 1102 that is connected to a screw conveyor 1104. The screw conveyor 1104 is similar to an Archimedes screw, which is mounted horizontally. The flow reactor 1100 can be shown as being filled with granulate 1006. The granulate 1006 comprises walnut shell grains or particles 100 such as is shown in Figs. 1-4. As the rotatable shaft 1102 is turned, it causes the granulate 1006 to move through the flow reactor 1100. It also causes the granulate 1006 to be mixed. At an entrance there is an inlet 1108 for adding granulate 1006. This may be done on a continual basis as the shaft 1102 is rotated. This causes the granulate to go to a first inlet for at least one pigment and fluid binding agent. At this first inlet 1110 the at least one pigment and the fluid binding agent are added to the granulate 1006 and become mixed with it as the shaft 1102 is rotated. When they are thoroughly mixed, the granulate 1006 and the at least one pigment and the fluid binding agent form an initial composition 1120. This initial composition 1120 is then transported beneath a first inlet for water and catalyst 1112. The water and catalyst may be added on a continual or intermittent basis at this inlet 1112.

[0102] As the initial composition 1120 is transported further along the flow reactor 1100 fluid binding agent and at least one pigment cure into the first coating 200 such as depicted in Fig. 2. After the initial coating 200 is formed, the initial composition 1120 is transported underneath the second inlet for at least one pigment and fluid binding agent. At this point more of the pigment and fluid binding agent are added and the initial composition 1120 becomes the subsequent composition 1122. The pigments used for the initial composition and the subsequent composition may be identical or they may be different.

[0103] The subsequent composition 1122 is mixed and transported underneath the second inlet for water and catalyst 1116. The water and catalyst are then mixed with the subsequent composition 1122 and over time are further transported to the end of the flow reactor 1100. By the time the subsequent composition 1122 has reached the end of the flow reactor 1100 the subsequent coating 300 has formed on the grains or particles of the granulate 1006 such as depicted in Fig. 3. At the very end, then the granulate 1006 exits the flow reactor 1100 at an outlet 1117. The granulate 1006 at this point is then artificial turf infill 602. The artificial turf infill 602 is then shown as entering into an optional dryer 1118.

[0104] It is clear from Fig. 11 that the flow reactor may also be extended. For example if it is desired to put a third or fourth or even more coatings, the number of inlets in the flow reactor 1100 can simply be increased. This may involve moving the granulate at a different rotational rate or possibly even making the flow reactor 1100 longer.

[0105] Fig. 12 is a photo of a walnut shell granulate covered by a brownish PU coating.

Listofreferencenumerals

[0106] 

100

walnut shell grain or granule

200

initial/first coating

202

gap

300

subsequent /second coating

400

further coating

500

artificial turf carpet

502

backing

504

artificial turf fiber tufts

506

row spacing

508

pile height

510

ground or floor

600

artificial turf

602

artificial turf infill

700

providing an initial composition comprising a granulate

702

mixing the initial composition

704

adding water and a catalyst to the initial composition during the mixing of the initial composition to cure the fluid PU reaction mixture into an initial coating of the granulate

706

providing a subsequent composition comprising the granulate with the initial coating

708

mixing the subsequent composition

710

adding water and the catalyst to the subsequent composition during the mixing of the subsequent composition to cure the fluid PU reaction mixture into a subsequent coating of the granulate

712

providing the granulate with the subsequent coating as artificial turf infill

800

providing a subsequent composition by adding the fluid PU reaction mixture to the granulate

802

mixing the subsequent composition

804

adding water and the catalyst to the subsequent composition during the mixing of the subsequent composition to cure the fluid PU reaction mixture into a further coating

900

installing an artificial turf carpet with multiple artificial turf fiber tufts

902

providing the artificial turf by spreading a layer of artificial turf infill between the multiple artificial turf fiber tufts

1000

mixing vat

1002

rotatable shaft

1004

mixing paddles

1006

granulate

1100

flow reactor

1102

rotatable shaft

1104

screw conveyor

1108

inlet for granulate

1110

first inlet for at least one pigment and fluid binding agent

1112

first inlet for water and catalyst

1114

second inlet for at least one pigment and fluid binding agent

1116

first inlet for water and catalyst

1117

outlet

1118

dryer

1120

initial composition

1122

subsequent composition

Claims

1. Artificial turf infill (602), wherein the artificial turf infill comprises walnut shell granulate (100) having one or more PU coatings (200, 300, 400).

2. The artificial turf infill of claim 1, wherein at least one of the one or more coatings is completely closed and free of gaps (202).

3. The artificial turf infill of claim 1, wherein each of the one or more coatings comprises gaps (202), wherein the gaps of the one or more coatings allow water to penetrate the one or more coatings and reach the walnut shell granulates.

4. The artificial turf infill of any one of the previous claims, wherein each of the one or more coatings is free of a pigment.

5. The artificial turf infill of any one of the previous claims, wherein the walnut shell granulate comprises at least two coatings (200, 300, 400).

6. The artificial turf infill of any one of the previous claims, wherein at least one of the one or more coatings comprises one or more types of pigment, preferably bright pigments.

7. The artificial turf infill of any one of the previous claims, wherein the walnut shell granulate without the two or more coatings has an average diameter between 0.1 mm and 4.0 mm, preferably between 0.4 mm and 3.0 mm, and/or wherein the walnut shell granulate without the two or more coatings has a maximum diameter less than 5.0 mm.

8. The artificial turf infill of any one of the previous claims, wherein the one or more PU coatings are elastic.

9. The artificial turf infill of any one of the previous claims, each of the one or more PU coatings being free of antimicrobial substances.

10. The artificial turf infill of any one of the previous claims, further comprising sand and/or rubber granulate.

11. The artificial turf infill of any one of the previous claims, wherein the one or more PU coatings are free of a pigment and wherein the artificial turf infill further comprises sand.

12. The artificial turf infill of any one of the previous claims, wherein the one or more PU coatings are free of a pigment and wherein the artificial turf infill further comprises a rubber granulate, the rubber granulate comprising or being coated with one or more ochre colored pigments.

13. An artificial turf (600), wherein the artificial turf comprises:

- an artificial turf carpet (500), wherein the artificial turf carpet comprises multiple artificial turf fiber tufts (504); and

- artificial turf infill (602) according to any one of the previous claims, the artificial turf infill being spread between the multiple artificial fiber tufts.

14. A method manufacturing artificial turf infill (602), wherein the method comprises:

- providing (700) an initial composition (1120) comprising a walnut shell granulate (1006), and a fluid PU reaction mixture;

- mixing (702) the initial composition;

- adding (704) water and a catalyst to the initial composition during the mixing of the initial composition to cure the fluid PU reaction mixture into a first PU coating (200) of the walnut shell granulate;

- providing (712) the PU coated walnut shell granulate as the artificial turf infill.

15. The method of claim 14, further comprising:

- providing (706) a subsequent composition (1122) comprising the walnut shell granulate with the first PU coating, and a further fluid PU reaction mixture;

- mixing (708) the subsequent composition;

- adding (710) water and the catalyst to the subsequent composition during the mixing of the subsequent composition to cure the fluid binding agent a second PU coating (300) of the walnut shell granulate; and

- providing (712) the PU coated walnut shell granulate with the first and second coating as the artificial turf infill.

16. The method of any one of claims 14-15, wherein the initial and/or the subsequent composition is free of a pigment, the method further comprising:

- mixing the PU coated walnut shell granulate with sand and/or with a PU-coated rubber granulate for providing a multi-component infill mixture, the coating of the rubber granulate comprising one or more ochre colored pigments; and

- using the multi-component infill mixture as the artificial turf infill.

17. The method of any one of claims 14-16, wherein the initial and/or the subsequent composition respectively comprise one or more additives, the additive being selected from a group comprising: a first type of pigment, a second type of pigment, a flame retardant, aluminum trihydrate, magnesium hydroxide, an intumescent component, ammonium polyphosphate, exfoliated graphite, methylcellulose, zeolite, an IR reflective pigment, a hindered amine light stabilizer, an anti-freeze additive, a de-icing additive, sodium chloride, potassium chloride, sodium formiate, potassium formiate, and combinations thereof.

18. The method of any one of claims 14-17, wherein the initial and/or the subsequent composition respectively comprise one or more additional types of granulate, the additional type of granulate being selected from a group comprising rubber, an elastomeric polymer, Metallocene Butadiene Rubber, nitrile rubber granulate, natural rubber granulate, styrene-butadiene rubber granulate, ethylene propylene diene monomer rubber granulate, black crumb rubber granulate, acrylonitrile butadiene rubber, a thermoplastic polymer, Styrene Ethylene Butylene Styrene , Styrene Block Copolymers, an elastic foam, elastic polyurethane foam, and combinations thereof.

19. The method of any one of claims 14-18, wherein the PU reaction mixture of the initial and/or of the subsequent composition comprises one or more MDI monomers, a partially polymerized polymer, an isocyanate and a catalyst.

20. A method of manufacturing artificial turf (600), wherein the method further comprises:

- installing (900) an artificial turf carpet (500), wherein the artificial turf carpet comprises multiple artificial turf fiber tufts (504); and

- providing (902) the artificial turf by spreading a layer of artificial turf infill (602) according to any one of claims 1-13 between the multiple artificial turf fiber tufts.

Drawing