Artificial turf fibers containing siloxane-grafted polymers

Abstract

The present invention provides artificial turf fibers comprising one or more siloxane-grafted polymers, where the polymer is a polyolefin or a polyamide.

Description

[Technical Field]

[0001] The present invention relates to artificial turf fibers and the manufacture of artificial turf fibers. The present invention further relates to artificial turf comprising the artificial turf fibers. [Background technology]

[0002] Artificial turf or artificial grass is a surface composed of fibers used to replace natural grass. The structure of artificial turf is designed so that the artificial turf has a grass-like appearance. Typically, artificial turf is used as a surface for playing fields or athletic fields, and for sports such as soccer, American football, rugby, tennis, and golf. In addition, artificial turf is frequently used in landscaping applications.

[0003] An advantage of using artificial turf is that it eliminates the need for regular grass playing or landscaping maintenance, such as mowing, fertilizing, and watering. Watering can be difficult, for example, due to local restrictions on water use. In other climate zones, turf regeneration and re-establishment of a closed turf cover is slower than damage to natural grass surfaces caused by play and / or exercise on the field.

[0004] The production of artificial turf fibers is often a technical challenge due to a variety of potential problems such as fiber tearing or sticking of the extrusion nozzle, etc. Additives used to address these problems often result in undesirable mechanical and / or chemical properties in the resulting artificial turf fibers.

[0005] EP4012082A2 discloses the use of siloxanes to reduce the rolling resistance of artificial grass sports surfaces and provide a sufficiently slippery surface without the need to water the artificial surface. To achieve this, free siloxanes are used that are selected so that they can migrate to the fiber surface during the production of the material. EP4012082A2 teaches the use of siloxanes that make the fiber surface slippery so that the playing properties of the field are similar to those of a watered field, for example, an irrigated hockey field.

[0006] Japanese Patent Application No. JPH09268514A teaches the addition of silicone-grafted polymers to improve resistance to permanent set and mechanical strength in relation to yarns used in artificial turf. However, this application is not concerned with improving the composition of process additives used in the manufacture of artificial turf. Furthermore, JPH09268514A teaches the use of very high amounts of silicone-grafted polymers, i.e., 0.5 to 30 parts by weight, preferably 1 to 15 parts by weight, which has been observed to result in undesirable fiber properties, particularly a slippery fiber surface and an increased tendency for delamination. EP3137682B1 describes the use of nucleating agents to increase the surface roughness of artificial turf fibers in order to more firmly integrate the fibers into the backing. Summary of the Invention

[0007] The present invention provides an artificial turf fiber and a method for manufacturing an artificial turf fiber as set forth in the independent claims. Embodiments are set forth in the dependent claims. The embodiments and examples disclosed herein can be freely combined with each other if they are not mutually exclusive.

[0008] In one aspect, the present invention relates to artificial turf fibers comprising one or more siloxane-grafted polymers, where the polymer is a polyolefin or a polyamide.

[0009] This can be advantageous because the polymers grafted with siloxanes allow for a good compromise in terms of smoothness and slipperiness of the artificial turf fibers: siloxane-grafted polyolefins or polyamides make it possible to produce artificial turf fibers that are smooth enough to prevent skin burns when players slide along the turf. At the same time, the grafting process creates large molecules with polyolefin- or polyamide-like properties that are immobile, so they are not too slippery (which would make the player slip, which is undesirable).

[0010] Furthermore, the siloxane-grafted polymers allow for a good compromise between the technical problems encountered during the extrusion process to produce artificial turf fibers, on the one hand, and the desired level of slipperiness of the artificial turf fibers, on the other hand: the applicant observed that even very small amounts of siloxane-grafted polymer effectively prevent clogging of the extrusion nozzle. This is advantageous because high amounts make the surface of the fibers very slippery, leading to the fibers being easily pulled out of the backing, thereby making the artificial turf more susceptible to wear and tear. In prior art, such as that represented by EP 3137682 B1, additional additives such as nucleating agents must be added to increase the surface roughness of the fibers to ensure that the fibers are firmly integrated into the backing, and it has been observed that some conventional processing aids counteract the effect of the nucleating agents by dramatically increasing the slipperiness of the fiber surface. The applicant surprisingly observed that even very small amounts of siloxane-grafted polymer can prevent nozzle clogging, and that these small amounts do not reduce the surface roughness to unacceptable values. Thus, embodiments of the present invention make it possible to produce artificial turf fibres that can be tightly integrated into the artificial turf backing, yet the extrusion process can be carried out without failures caused by clogging of the extrusion nozzle.

[0011] An additional advantage is that siloxane-grafted polymers can be used as processing aids to improve the extrusion process for obtaining artificial turf fibers. Siloxane-grafted polyolefins or polyamides increase lubricity and reduce the surface adhesion of the extruded polymer mass. In the extrusion of polymer fibers, problems often arise in which the viscosity and surface adhesion of the polymer mass are too high, completely or partially clogging the nozzle. Deposits on the extrusion screw and extrusion coat lead to increased pressure, insufficient flow of the polymer melt, and reduced tool life. Furthermore, in extrusion orifices with complex geometries, if the viscosity of the polymer mass is too high, the extruded polymer mass can adhere to the metal surface of the extrusion nozzle, thereby reducing the extrusion rate at the periphery of the fiber / extrusion orifice relative to the rate at the center of the fiber / extrusion orifice. This can lead to damage to the extruded fiber due to the high flow rate difference in different regions of the extrusion orifice. These different flow rates can be so severe that the polymer flow is interrupted and the extruded fiber breaks during the extrusion process. This can lead to failures and significant delays in the production process. Furthermore, oxidation aging of the buildup during the extrusion process on all heated metal surfaces in the extrusion line can result in deposits that are nearly impossible to remove and can impede flow up to the point of permanent damage to the line.

[0012] Adjusting the viscosity and surface adhesion of the polymer mass during extrusion is a challenge, particularly in the field of artificial turf fibers, because the lubricity and surface adhesion of the polymer mass must not be too high. Otherwise, the fibers may become too slippery and cause players to slip, or the fibers may not be able to withstand mechanical stress during play due to a lack of internal cohesion. The use of siloxane-grafted polymers as processing aids for artificial turf production can be particularly advantageous, as they can prevent complete or partial clogging of extrusion nozzles even in technically demanding and complex extrusion setups, such as the extrusion of polymer mixtures with multiple immiscible polymers, the coextrusion of polymers to achieve a desired polymer distribution profile, and / or extrusion through highly delicate extrusion nozzle profiles.

[0013] The use of siloxane-grafted polymers as processing aids can have the advantage that they are non-toxic. There have been reports that some halogenated compounds, such as some per- and polyfluoroalkyl substances (PFAS), that have been used as processing aids in the polymer industry are potentially toxic. Therefore, embodiments of the present invention can have the advantage that artificial turf fibers do not contain toxic processing aids. Embodiments of the present invention allow for the creation of artificial turf fibers that are free of halogenated compounds and physiologically harmless. This is particularly advantageous in the field of artificial turf fibers, because they regularly come into skin contact with athletes. In some cases, artificial turf surfaces are installed in private gardens and children's playgrounds, so the health safety of the fibers is particularly important here.

[0014] A further advantage may be that siloxane-grafted polymers are highly effective and thermally stable and therefore more suitable for extrusion processes than, for example, fatty acids, which at least partially decompose due to the high temperatures during extrusion.

[0015] A further advantage is that the siloxane-grafted polyolefin or polyamide is not used directly as a processing aid or the like, but rather is grafted onto the polyolefin / polyamide. This can have the advantage that the migration ability of the additive within the polymer composition is reduced (due to both the high molecular weight and the polymer-like properties of the additive provided by the polyolefin or polyamide). This is advantageous in that separation of the additive from the polymer mass is prevented. More importantly, the sizing agent and the polyolefin or polyamide backbone ensure that the additive acquires polyolefin- or polyamide-like properties, making it easier to disperse the additive within the polymer mass and maintain it in a uniformly dispersed state. This has a positive effect on both the extrusion process and the subsequent use of the extruded fiber as an artificial turf fiber: due to reduced migration, the siloxane-grafted polymer cannot leave the fiber during use. At best, migration of this processing aid to the fiber surface is very slow, along a small concentration gradient that can result from some of the siloxane-grafted polymer leaving the fiber and / or being worn away by mechanical abrasion. The polyolefin- or polyamide-like properties also prevent the additive from clogging the orifices at certain points in the extrusion nozzle, thus preventing changes in the extruded fiber profile and fiber breakage during extrusion.

[0016] The polyolefin or polyamide grafted with one or more siloxanes is well mixed into the base polymer and integrated into the solidified fiber polymer mass. Due to its improved compatibility, it does not separate from the base polymer mass. Compared to high-flow lubricants such as spin finishes, it is immobile and does not migrate. Therefore, it does not adversely affect tuft binding like traditional additives such as fatty acid polyglycol esters.

[0017] According to embodiments, the artificial turf fibers are PFAS-free.

[0018] According to an embodiment, the artificial turf fibers are free of halogen compounds, in particular bromine compounds, fluorine compounds and chlorine compounds.

[0019] According to embodiments, the artificial turf fibers are free of free siloxanes (free siloxanes: siloxanes that are not bound to polyolefins or polyamides). In particular, according to embodiments, the artificial turf fibers are essentially free of siloxanes having a molecular weight of less than 500 Daltons.

[0020] This can be beneficial as some free siloxane and free silicone dispersions are suspected of impairing fetal fertility.

[0021] According to some embodiments, at least 50% of the molecules of the polymer grafted with one or more siloxanes have a molecular weight of at least 2,000 daltons. According to some embodiments, at least 50% of the polyolefin grafted with one or more siloxanes have a molecular weight of at least 10,000 daltons. According to some embodiments, at least 50% of the polyolefin grafted with one or more siloxanes have a molecular weight of at least 100,000 daltons, particularly at least 500,000 daltons. According to some embodiments, at least 90% of the molecules of the polymer grafted with one or more siloxanes have a molecular weight within the range of the amounts specified above.

[0022] The molecular weights specified herein can be determined, for example, by measuring the melt flow rate according to standards ASTM D1238 or ISO 1133.

[0023] According to an embodiment, the polymer in the one or more siloxane-grafted polymers is a non-polar polyolefin, such as polyethylene.

[0024] This can be beneficial because it can make polymers grafted with one or more siloxanes essentially nonpolar, facilitating their integration into the largely nonpolar base polymer matrix of fibers, such as PE-based fibers. Currently, siloxane-grafted polymers with an AB block format are commercially available, where the A block is a silicone, such as PDMS, and the B block is either a polyamide or polyacrylate. The A:B ratio of these siloxane block polymers can be, for example, 1:1. Because the dipole moment between the C atom and the N or O atom in the polyamide or polyacrylate block is very large, both B block variants are polar blocks, resulting in a polar polymer. The A block (e.g., PDMS) is also polar. Therefore, these polar-grafted polymers are not well suited for use with nonpolar fiber-based polymers, as polar and nonpolar polymers may not be miscible, resulting in artificial turf fibers that tend to delaminate.

[0025] According to an embodiment, the polymer grafted with one or more siloxanes has a grafting capacity of 500 to 600 kg / m 3 It has a bulk density of

[0026] For example, this may mean that the concentrations of said compounds in the artificial turf fibres are below their respective detection limits.

[0027] Siloxanes are commonly known as silicones. Their chemical structure determines the range of physicochemical properties, including toxicity and safety for human health. Generally, as the size of silicone particles decreases, the safety of application decreases. This is because low-molecular-weight siloxanes exhibit lipophilicity, which increases their ability to overcome biological membranes and skin barriers. According to the present invention, siloxanes are grafted onto polyolefins or polyamides. This increases the molecular weight of the siloxane, reducing its bioavailability and ability to migrate to the surface of artificial turf fibers.

[0028] According to an embodiment, the polyolefin is polyethylene or polypropylene.

[0029] According to an embodiment, the artificial turf fiber comprises or essentially consists of a base polymer, the major portion of which, for example at least 50% by weight, in particular at least 60% by weight, in particular at least 70% by weight, consists of polyethylene or polypropylene or polyamide. Preferably, the type of olefin in the one or more siloxane-grafted polyolefins is the same as the type of polymer that constitutes the major portion of the base polymer. Preferably, when polyamide constitutes the major portion of the base polymer, the polymer in the siloxane-grafted polymer is polyamide.

[0030] This can be advantageous because artificial turf fibers are often made from polyethylene, polypropylene, polyamide, or polymer blends containing two or more of these polymer types. Grafting siloxane onto a polyethylene molecule chemically mimics the properties of the entire molecule. This means that siloxane-grafted polyethylene can be mixed particularly well and uniformly with a polymer mass primarily consisting of polyethylene. Similarly, polypropylene grafted with one or more siloxanes can be mixed uniformly and stably with a polymer mass primarily consisting of polypropylene. This can be advantageous because uneven distribution of the additive and / or subsequent phase separation of the additive and the polymer mass can completely or partially clog the extraction nozzle, leading to loss or distortion of the microstructure of the fiber profile or fiber breakage during the extraction process. Furthermore, applicants have observed that the very similar chemical properties of the olefin used to synthesize the siloxane-grafted olefin and the polymer that is the major part of the base polymer can help ensure that the siloxane-grafted polymer does not migrate to the surface of the fiber during the extrusion process. This can ensure that the fiber surface is not too slippery, but is rough enough to allow firm integration into the artificial turf substrate.

[0031] According to an embodiment, at least 0.01% by weight of the artificial turf fibers consists of a polymer grafted with one or more siloxanes, in particular 0.01% to 0.25% by weight of the artificial turf fibers, in particular 0.01% to 0.09% by weight of the artificial turf fibers, in particular 0.01% to 0.08% by weight of the artificial turf fibers, in particular 0.01% to 0.07% by weight of the artificial turf fibers, in particular 0.01% to 0.06% by weight of the artificial turf fibers, in particular 0.01% to 0.05% by weight of the artificial turf fibers, in particular 0.02 to 0.03% by weight of the artificial turf fibers.

[0032] According to an embodiment, no more than 0.25% by weight of the artificial turf fibers consists of one or more siloxane-grafted polymers.

[0033] The applicant has observed that the above-mentioned amount ranges provide artificial turf fibers with very desirable properties both in terms of the extrusion process (no clogging, no distortion of the fiber profile, no fiber tearing) and in terms of playing properties: the fibers are resistant to wear and tear and do not delaminate. Nevertheless, they have a smooth, but not too slippery, surface. The above-mentioned amount ranges provide a very good compromise in terms of smoothness and slipperiness. That is, when the siloxane-grafted polymer is added in the above-mentioned amount ranges, the fibers are smooth enough to prevent skin burns when players slide or glide along the turf. At the same time, the fibers are not too slippery, which would cause players to slip.

[0034] The applicant surprisingly observed that an amount of one or more siloxane-grafted polyolefins or polyamides of 0.25% by weight or less, or even 0.09% by weight or less, or even 0.07% by weight or less, and in some cases 0.05% by weight or less of the fiber, of the artificial turf fiber is sufficient to ensure a smooth extrusion process of monofilaments or polymer films, even monofilaments with a filigree fiber profile. A further advantage is that the resulting artificial turf fiber has very good playing properties that have been observed to deteriorate when the amount of additive increases significantly above 0.25% by weight of the resulting fiber. This is because limiting the amount of one or more siloxane-grafted olefins to the 0.25% threshold ensures that the fiber surface is smooth enough to prevent skin burns, yet rough enough to prevent players from slipping and falling. Furthermore, this threshold amount ensures that the surface roughness of the artificial turf fiber is still high enough to allow the fiber to be firmly integrated into a carrier via a secondary backing. In some embodiments, the artificial fibers are integrated into a carrier (e.g., by tufting, weaving, etc.), and then a liquid secondary backing, such as a liquid polyurethane mass or a liquid latex mass, is applied onto at least one side of the carrier, thereby contacting and wetting at least some of the integrated fibers. When the liquid secondary backing solidifies, the artificial turf fibers are firmly integrated into the backing. If the amount of one or more siloxane-grafted polymers is too high, the resulting fibers may have too low a surface roughness, which may result in the fibers being pulled out of the backing as a result of wear and tear.

[0035] According to an embodiment, the polymer grafted with one or more siloxanes is a graft copolymer in which multiple siloxane side chain blocks are grafted onto a main chain made of a polymer, for example a polyolefin or polyamide.

[0036] According to an embodiment, the siloxane is an organomodified siloxane (OMS).

[0037] An example of an organically modified polydimethylsiloxane that can be used to graft the siloxane onto a polyolefin or polyamide has the CAS number: 68937-54-2, which refers to a methylsiloxane-dimethylsiloxane copolymer available, for example, as "Silquest® PA-1 organosilicon."

[0038] According to embodiments, the siloxane is polydimethylsiloxane (PDMS), particularly a PDMS having more than 40 repeating monomer [Si(CH3)2O] units, particularly a PDMS having more than 50 repeating monomer [Si(CH3)2O] units, and especially a PDMS having 50-80 repeating monomer [Si(CH3)2O] units. These siloxanes, when grafted onto polymers, have been observed to provide particularly effective processing aids that have very little tendency to migrate from fibers and / or cause delamination.

[0039] According to an embodiment, the molecular weight of the siloxane (siloxane chain already grafted to the polymer chain or used to be grafted) has a molecular weight of more than 3000 daltons, in particular between 4000 and 6000 daltons.

[0040] Molecular weight and number of repeating monomer units can be determined using exclusion chromatography with an evaporative light scattering detector as described in "Size Exclusion Chromatography with Evaporative Light Scattering Detection (SEC-ELSD) as a Method for Speciation Analysis of Polydimethylsiloxanes III. Identification and Determination of Dimethicone and Simethicone in Pharmaceutical Formulations," Krystyna Mojsiewicz-Pienkowska, Journal of Pharmaceutical and Biomedical Analysis 58 (2012) 200-207.

[0041] This can have the advantage that siloxanes in this molecular weight range have low viscosity, allowing for good reduction of friction during the extrusion process. Siloxane groups with significantly higher molecular weights pose compatibility problems with the polymer (e.g., PE) used as the backbone for the grafting process.

[0042] According to an embodiment, the polymer grafted with one or more siloxanes has a molecular weight of more than 500 daltons, in particular more than 10,000 daltons, preferably more than 100,000 daltons, in particular at least 500,000 daltons.

[0043] The molecular weight of the polymer grafted with one or more siloxanes is measured by the melt flow rate according to the ASTM D1238 standard.

[0044] According to embodiments, the polymer grafted with one or more siloxanes is solid at room temperature or has a waxy consistency at room temperature. As used herein, the term room temperature refers to a temperature of 20° C. The viscosity may depend on the ratio of siloxane to polymer.

[0045] According to an embodiment, the acid number (calculated on the non-volatile content) of the siloxane grafted onto the polymer is about 0.5 mg KOH / g (+ / - 10%).

[0046] According to an embodiment, the OH-content (calculated for the non-volatile content) of the siloxane grafted onto the polymer is about 48 mg KOH / g (+ / - 10%).

[0047] The use of one or more siloxane-grafted polymers that are solid or waxy at room temperature can have the advantage that the consistency is similar to that of typical artificial turf fiber materials at room temperature. Furthermore, the essentially solid or waxy state prevents the grafted polymer from migrating to the surface of the fiber and away from the fiber.

[0048] According to some examples, commercially available polymers grafted with one or more siloxanes, for example, organically modified siloxanes (OMS) on a polyethylene carrier such as Tegomer® 6810, are used.

[0049] According to some examples, carbinol-functionalized polydimethylsiloxane (PDMS) is used as the siloxane grafted onto the polyolefin or polyamide backbone. According to embodiments, the artificial turf fiber includes two or more protrusions extending in different directions from the center of the fiber.

[0050] This may have the advantage of more faithfully reproducing the appearance and feel of natural grass cutting blades. The applicant observed that extruding polymer fibers through an extrusion nozzle with a complex filigree profile increases the risk of clogging and fiber breakage. The applicant surprisingly observed that adding one or more siloxane-grafted polymers to the base polymer can prevent or at least significantly reduce these problems. This is because it significantly reduces adhesion of the polymer to the extrusion nozzle walls and reduces the mass velocity differential and shear forces of the polymer at the extrusion nozzle. Therefore, artificial turf fibers made from polymers containing this additive can achieve highly complex filigree fiber profiles that accurately mimic the appearance and feel of natural grass.

[0051] According to an embodiment, the profile of at least one of the protrusions comprises a concave side and / or a wavy section covering at least 60% of one side of said at least one protrusion.

[0052] The wavy sections allow for the imitation of grooves and plant veins, which can be observed on the underside and sometimes also on the topside of some grasses, thus allowing for the specific reproduction of the surface structure of a particular grass species. The use of concave edges can serve the same purpose and / or help to save material without reducing the stability of the fibers. This can reduce material and transportation costs and also improve gameability.

[0053] According to an embodiment, the artificial turf fibers include a base polymer, and one or more siloxane-grafted polymers are dispersed in the base polymer.

[0054] According to embodiments, the major portion of the base polymer is selected from the group consisting of polyethylene (PE), polypropylene (PP), polyamide (PA), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). For example, the major portion may mean at least 50% by weight, or at least 60% by weight, or at least 70% by weight, or at least 80% by weight, or at least 90% by weight, or at least 95% by weight of the polymer. In some embodiments, the base polymer is a combination of two or more of the aforementioned polymers. For example, the base polymer may be a blend of multiple different polymers. Compatibilizers may be used to combine immiscible polymer types.

[0055] According to an embodiment, the artificial turf fibers are extruded fibers.

[0056] According to embodiments, the artificial turf fibers are extruded fibers made by extruding a base polymer comprising a mixture of two or more immiscible polymers.

[0057] According to embodiments, the artificial turf fibers are extruded fibers made by co-extruding two or more polymers through the same extrusion nozzle to form a desired polymer distribution profile in the fiber. For example, the desired polymer distribution profile may be a core-clad pattern.

[0058] According to an embodiment, the base polymer comprises a first polymer, a second polymer, and a compatibilizer, wherein the first polymer and the second polymer are immiscible, and the first polymer forms thread-like regions surrounded by the compatibilizer within the second polymer.

[0059] According to embodiments, the first polymer is any one of polyamide, polyethylene terephthalate (PET), and polybutylene terephthalate (PBT), and additionally or alternatively, the second polymer is any one of polyethylene, polypropylene, and mixtures thereof.

[0060] According to an embodiment, the first polymer is a polar polymer, for example PA, and the second polymer is a non-polar polymer, for example PE.

[0061] According to embodiments, the compatibilizer is any one of maleic acid grafted to polyethylene or polyamide; maleic anhydride grafted to a free-radical initiated graft copolymer of polyethylene, SEBS, EVA, EPD, or polypropylene with an unsaturated acid or its anhydride (e.g., maleic acid, glycidyl methacrylate, ricinolol oxazoline maleinate); a graft copolymer of SEBS and glycidyl methacrylate, a graft copolymer of EVA with mercaptoacetic acid and maleic anhydride; a graft copolymer of EPDM and maleic anhydride; a graft copolymer of polypropylene and maleic anhydride; a polyolefin-graft-polyamide, polyethylene, or polyamide; and a polyacrylic acid type compatibilizer.

[0062] The use of a compatibilizer can have the advantage that immiscible polymers do not delaminate from each other. The first polymer forms beads within the second polymer, which are then converted into thread-like regions embedded in the second polymer during the extrusion process. The thread-like regions may be further stretched in any drawing step applied to the extruded monofilament. The compatibilizer ensures that the first polymer and the second polymer within the thread-like regions do not delaminate.

[0063] The use of a first polymer and a second polymer allows for tailoring of the properties of the artificial turf fiber. For example, a softer plastic can be used for the second polymer to give the artificial turf a softer feel, more like natural grass. A stiffer plastic can be used for the first polymer or other immiscible polymer to give the artificial turf greater elasticity and stability, as well as the ability to bounce back after being stepped on or pressed down.

[0064] A further advantage may possibly be that during the extrusion process, the thread-like regions are concentrated in the central region of the monofilament. This concentrates the stiffer material in the center of the monofilament and the greater amount of softer plastic in the outer or exterior regions of the monofilament. This may further result in artificial turf fibers with more grass-like properties.

[0065] A further benefit may be that the artificial turf fibres have improved long term resilience, which may require less maintenance of the artificial turf and less brushing of the fibres as the fibres will more naturally recover and stand up after use or being trampled on.

[0066] However, the use of two or more different, immiscible polymers can have the disadvantage of increasing the risk of delamination of the artificial turf fiber during use and increasing the risk of phase separation during the extrusion process, which can lead to clogging of the extrusion nozzle or fiber breakage. These problems are caused by the tendency of the immiscible polymers to separate into different phases, which can cause the phase with higher adhesion to the metal wall of the extruder to accumulate in the extrusion nozzle and cause the problems mentioned above. Surprisingly, it has been observed that the addition of one or more siloxane-grafted polymers can prevent these problems and thereby improve the production of artificial turf fibers containing two or more immiscible polymers, such as PE and PA.

[0067] According to an embodiment, the fiber comprises 60-99% LLDPE polymer by weight of the fiber and 1-15% LDPE polymer by weight of the fiber. For example, the fiber may be produced by extruding a base polymer comprising 60-99% LLDPE polymer and 1-15% LDPE polymer by weight of the fiber.

[0068] According to some embodiments, the artificial turf fiber comprises a first polymer forming thread-like regions within a second polymer, the second polymer comprising 60-99% LLDPE polymer by weight of the second polymer and 1-15% LDPE polymer by weight of the second polymer.

[0069] According to an embodiment, the LLDPE polymer has a viscosity of 0.918 g / cm 3 ~0.920g / cm 3 and LDPE polymers have densities in the range of 0.919 g / cm 3 ~0.921g / cm 3 It has a density in the range of

[0070] It can be advantageous for several reasons to manufacture artificial turf comprising a blend of LLDPE and LDPE in the above specified amount ranges, also including one or more siloxane-grafted polymers, to create monofilaments in an extrusion and drawing process.

[0071] This method makes it possible to produce artificial turf fibers that are simultaneously soft, flexible, resistant to shear forces (e.g., applied during extrusion or drawing), have high tensile strength, and are resistant to splicing, thereby protecting the extrusion nozzle from partial or complete clogging caused by crystalline parts adhering to the inner walls of the extrusion nozzle. As used herein, "splice" refers to splitting the fiber along its longitudinal axis.

[0072] Compared to plastomers in combination with LLDPE or HDPE, base polymers that are polymer blends containing a specific amount range of LLDPE and LDPE in combination exhibit increased softness, flexibility, and improved tensile strength, while exhibiting the same or even improved resistance to splitting. It has been observed that not all plastomers are sufficiently suitable for preventing splitting of artificial turf fibers, possibly because plastomers, at least when provided in certain amount ranges and / or with certain densities, do not produce the chain entanglements that can reliably prevent splicing and / or appear to have negative side effects, such as producing fibers with reduced tensile strength or flexibility and / or increased brittleness.

[0073] The applicant has observed that by combining specific amounts of LLDPE and LDPE polymers to produce artificial turf fibers, an optimal compromise can be achieved between high splicing resistance on the one hand and high tensile strength on the other. The fibers may further be less brittle and more flexible. The applicant has also observed that to ensure high resistance to splicing combined with high tensile strength and flexibility of the resulting fibers, the amount of LDPE used should be relatively low, preferably in the range of 1% to 15% by weight of the polymer mixture, more preferably in the range of 5% to 8% by weight.

[0074] The applicant observed that the lack of long-chain branching in LLDPE allows the chains to slide against each other during elongation without entanglement. As a result, fibers composed entirely of LLDPE are susceptible to splicing when tension is applied to the surface of the fiber. The applicant also observed that LLDPE has higher tensile strength and higher puncture resistance than LDPE and many plastomers. By using a specific combination of LDPE and LLDPE in the specific amount ranges described above, it is possible to produce artificial turf fibers that can withstand splicing while also being soft, flexible, and having high tensile strength.

[0075] The stretch-induced formation of polymer crystals inside and on the surface of the monofilament increases the fiber's roughness, thereby enabling strong mechanical fixation in artificial turf backings in embodiments where the monofilament is partially embedded in a liquid film that subsequently solidifies, such as a latex or PU film. However, the crystals formed during the extrusion process also have drawbacks, as they can clog the nozzle or increase the risk of fiber breakage during the extrusion process. However, these risks can be significantly reduced by adding one or more siloxane-grafted polymers to the base polymer.

[0076] Applicant has further observed that applying strong shear forces to a polymer mixture containing LLDPE and LDPE polymers, for example by extruding the polymer mixture, causes the LDPE molecules to deform, and the side branches of the LDPE molecules to become entangled with other LDPE molecules and / or with LLDPE molecules. As a result of chain entanglement, viscosity and the risk of nozzle clogging or distorted fiber profiles increase. Applicant has found that artificial turf fibers made from specific blends of LDPE and LLDPE in specific amounts, which also contain one or more siloxane-grafted polyolefins or polyamides, are soft and flexible, have high tensile strength (thanks to the LLDPE component), and are simultaneously resistant to splicing (thanks to chain entanglement caused by the LDPE component) and the aforementioned manufacturing problems. Applicant has observed that if the ratio of LLDPE to LDPE is too high, splicing may occur, and if the ratio is too low, the flexibility and tensile strength of the fiber may be significantly reduced.

[0077] In contrast to polymers such as polyamide (PA), polyethylene (PE) is generally considered a relatively soft and flexible polymer, reducing the risk of injuries such as skin burns. LLDPE is a form of PE that is shear-sensitive due to its shorter chain branching. LLDPE allows for faster stress relaxation of the polymer chains after extrusion or drawing compared to the stress relaxation of LDPE of a comparable melt index. Stress resistance can be particularly beneficial in the context of artificial turf fiber manufacturing: the drawing process causes the formation of crystalline moieties on the surface (and interior) of the drawn fiber. The crystals increase surface roughness, thus allowing for better mechanical anchoring of the fiber in the surface backing.

[0078] According to an embodiment, the base polymer is a polymer mixture comprising LDPE polymer in an amount of 5-8% by weight of the polymer mixture and LLDPE polymer in an amount of 60-95% by weight of the polymer mixture. According to a preferred embodiment, the polymer mixture comprises LDPE polymer in an amount of 5-8% by weight of the polymer mixture and / or LLDPE polymer in an amount of 65-75% by weight of the LLDPE polymer mixture.

[0079] A "polymer mixture" may include additional substances, such as filler materials and / or additives, and therefore the total amounts of LLDPE polymer and LDPE polymer need not add up to 100% by weight of the polymer mixture.

[0080] According to an embodiment, the LDPE polymer has a viscosity of 0.919 g / cm 3 ~0.921g / cm 3 It has a density in the range of

[0081] According to some embodiments, the LLDPE has a viscosity of 0.918 g / cm 3 ~0.920g / cm 3 It has a density in the range of

[0082] Applicants have surprisingly observed that the ability of a fiber to resist splicing and exhibit high tensile strength also depends on the density of the respective polymer. This is likely because density corresponds to the number and position of branches and other structural features related to branching of the PE molecule. The above density ranges have been observed to be particularly suitable for providing fibers that combine splicing resistance with tensile strength.

[0083] According to another embodiment, the LLDPE polymer has a viscosity of 0.918 g / cm 3 ~0.920g / cm 3 and a first LLDPE polymer having a density in the range of 0.914 g / cm 3 ~0.918g / cm 3 and a second LLDPE polymer having a density in the range of

[0084] According to an embodiment, the polymer blend comprises the second LLDPE polymer in an amount of 7 to 13% by weight of the polymer blend, with the remainder of the LLDPE polymer in the blend consisting of the above-specified higher density first LLDPE.

[0085] Adding a second "low-density" LLDPE in addition to the first "medium-density" LDPE can be advantageous because it further reduces the risk of splicing: the low-density LLDPE folds in three-dimensional space in a less dense manner (see Figure 1), thus reducing the amount of crystalline material produced during the drawing process. This reduces the brittleness of the fiber and therefore the risk of splicing. Therefore, by selecting specific amounts of LDPE and LLDPE, splicing can be prevented by promoting chain entanglement, thereby further reducing the risk of splicing by adding the low-density LLDPE.

[0086] In a further beneficial aspect, the addition of an amount of said "low density" LDPE makes the fibers smoother and reduces the risk of skin burns.

[0087] According to an embodiment, the LLDPE polymer is added to the polymer mixture in the following form: - a "main" LLDPE polymer component without additives. The "main" or "pure" LLDPE polymer may be added, for example, in an amount of 47-88% by weight of the polymer mixture, preferentially in an amount of 70-75% by weight of the polymer mixture. - a further LLDPE polymer containing one or more additives. The second LLDPE polymer is added, for example, in an amount of 7-13% by weight of the polymer mixture, preferentially in an amount of about 10% by weight. The additive-containing LLDPE polymer may also be called a "masterbatch". The "main" LLDPE polymer component and the masterbatch have a concentration of 0.918 g / cm 3 ~0.920g / cm 3 The density range may be as mentioned above. Optionally, a low density LLDPE polymer may be added, preferentially in an amount of 7 to 13% by weight of the polymer mixture.

[0088] Preferentially, the LLDPE polymer type of the main LLDPE component and the LLDPE polymer type of the "masterbatch" are identical; the only difference is that the masterbatch further contains additives. For example, LDPE, the LLDPE masterbatch, and the additive-free LLDPE component(s) can each be added to a container in the form of polymer granules. The granules are mixed and heated until all the polymer granules melt and produce the liquid polymer mixture used to extrude the monofilament. Adding additives solely through a separate masterbatch based on the main type of polymer (here, LLDPE polymer) can be advantageous because it allows for the modification of certain properties, such as color and flame retardant content, independently of the type and relative amounts of the LLDPE and LDPE polymers, each lacking additives. Thus, it is possible to modify, for example, the color or concentration of flame retardant without departing from the optimal ratio of LLDPE to LDPE. Similarly, it is possible to slightly adapt the ratio of medium to low density LLDPE without changing the concentration of additives in order to "fine tune" the physicochemical properties of the monofilaments and fibers, such as elasticity, resistance to shear and splicing, flexibility, softness and tensile strength.

[0089] According to an embodiment, the LLDPE polymer is a polymer made by a polymerization reaction in the presence of a Ziegler-Natta catalyst.

[0090] In some embodiments, the Ziegler-Natta catalyst is a heterogeneous supported catalyst based on a titanium compound in combination with a cocatalyst, such as an organoaluminum compound like triethylaluminum. In other embodiments, the Ziegler-Natta catalyst is a homogeneous catalyst. Homogeneous catalysts are typically based on Ti, Zr, or Hf complexes, preferably used in combination with a different organoaluminum cocatalyst, such as methylaluminoxane (MAO). The use of a Ziegler-Natta catalyst can have the advantage that the branches of the resulting LLDPE are more randomly distributed, e.g., exhibiting atactic orientation. This can facilitate entanglement of the LDPE molecules with the branches.

[0091] According to an embodiment, the LLDPE polymer is a polymer produced by a polymerization reaction in the presence of a metallocene catalyst. Using a metallocene to catalyze polymerization to produce an LLDPE polymer can be advantageous because this particular form of catalyst ensures that branching occurs in a more defined, less random, manner. As a result of using a metallocene as a catalyst, the number of branches per LLDPE molecule does not follow a normal distribution, but rather follows a distribution with only one or very few (e.g., 1-3) peaks in the frequency of branches per polymer molecule. Producing an LLDPE polymer with a more random distribution of branch lengths may facilitate entanglement with the branches of LDPE molecules.

[0092] For example, metallocene catalysts can be used with cocatalysts such as MAO and (Al(CH3)xOy)n. In some examples, metallocene catalysts have the composition Cp2MCl2 (M = Ti, Zr, Hf), such as titanocene dichloride. Typically, the organic ligand is a cyclopentadienyl derivative. Depending on the type of cyclopentadienyl ligand, for example, by using an anthra-bridge, metallocene catalysts can produce polymers with different tacticities and branching frequencies. A tactic macromolecule, as defined by the IUPAC, is a macromolecule in which essentially all of the configurational (repeat) units are identical. Tacticity, branching frequency, and distribution affect the physical properties of the polymer. The regularity of a polymer's structure affects the degree to which it possesses rigid, crystalline long-range order or flexible, amorphous long-range disorder. According to embodiments, the tacticity of polymer blends used to produce LLDPE or LDPE granules for use in artificial turf fiber production can be measured directly using proton or carbon-13 NMR. This technique allows for quantification of tacticity distribution by comparison of peak areas or integral ranges corresponding to known diads (r,m), triads (mm,rm+mr,rr), and / or higher order n-ads, depending on the spectral resolution. Other techniques that can be used to measure tacticity include X-ray powder diffraction, secondary ion mass spectrometry (SIMS), vibrational spectroscopy (FTIR), and especially two-dimensional techniques.

[0093] According to an embodiment, the LLDPE polymer is a polymer made by copolymerizing ethylene with 5-12% of an α-olefin having 3-8 carbon atoms, such as butene, hexene, or octane. The crystallinity of the resulting LLDPE depends on the amount of comonomer added and is typically in the range of only 30-40%, and the crystalline melting range is typically in the range of 121-125°C.

[0094] According to an embodiment, the LLDPE polymer is a polymer comprising 0.001 to 10 tertiary C atoms per 100 C atoms of the polymer chain. Preferably, the LLDPE polymer comprises 0.8 to 5 tertiary C atoms per 100 carbon atoms of the polymer chain.

[0095] According to an embodiment, the LDPE polymer is a polymer comprising more than 0.001, and preferentially more than 1, tertiary C atom per 100 C atoms of the polymer chain.

[0096] The number of tertiary C atoms is a measure of the degree of branching. Using LLDPE and / or LDPE polymers with the above-specified degrees of branching can be advantageous, as it has been observed that the branching causes strong entanglement between LLDPE and LDPE polymer molecules, which protects the polymer fibers from splicing. According to an embodiment, producing artificial turf fibers involves forming drawn monofilaments into a yarn. A plurality of monofilaments, for example, 4 to 8, can be formed or finished into a yarn.

[0097] According to an embodiment, the method further comprises weaving, spinning, twisting, rewinding and / or bundling the drawn monofilaments into artificial turf fibers. This technique for producing artificial turf is known, for example, from US Patent Application Publication No. 20120125474.

[0098] According to an embodiment, the polymer mixture is a liquid polymer mixture and includes two or more different liquid phases. The first of the phases includes a first dye and a polymer mixture component according to any one of the previously described embodiments. For example, the first phase may include a mixture of first and second LLDPE polymers and LDPE polymers. The second phase may include a second dye and an additional polymer, such as a polyamide, that is immiscible with the first phase. The second dye may have a different color from the first dye, and the additional polymer forms polymer beads within the first phase.

[0099] Stretching the reheated monofilament transforms the polymer beads into thread-like regions. Extrusion of the two-phase polymer mixture into a monofilament produces a monofilament that contains a marbled pattern of the first color of the first dye and the second color of the second dye.

[0100] Thus, a liquid polymer mixture can be created in which two different dyes are separated into two distinct phases, with one of the phases "emulsified" in the other phase in the form of beads. This can be advantageous because it avoids the need to use or create a customized extruder that mechanically prevents the two dyes from prematurely mixing, thereby ensuring that a marbled monofilament is created, rather than a monofilament with a color intermediate between the first and second colors. Thus, embodiments of the present invention allow for the creation of marbled monofilaments using the same extrusion machinery used to create single-color monofilaments. This can reduce production costs and increase the variety of artificial turf types that can be created with a single melt-extrusion device.

[0101] Furthermore, to provide artificial turf that accurately replicates the texture of natural grass, complex co-extrusion, which requires several extrusion heads to feed one complex spinneret tool, is not required.

[0102] In a further advantageous embodiment, even when two different types of polymers are used in two phases, such as various forms of PE in the first phase and polyamide in the second phase, the polymer mixture that makes up the first phase entirely or predominantly with the first dye may not peel off from the other polymer that makes up the second phase entirely or predominantly with the second dye. The thread-like regions are embedded within the polymer mixture in the first phase. Therefore, they cannot peel off.

[0103] According to embodiments, a compatibilizer is added to the polymer mixture to connect the first and second phases at the interface, thereby further preventing delamination of the polymers in the different phases.

[0104] A further advantage may be that, possibly due to fluid dynamics during the extrusion process, the thread-like regions are concentrated in the central region of the monofilament during the extrusion process, while a significant portion of the thread-like regions is still present on the surface of the monofilament to create a marbled appearance. Thus, the other polymer (which may be a stiffer material than the LLDPE and LDPE in the first phase) may be concentrated in the center of the monofilament, while a greater amount of the softer plastic may be concentrated on the exterior or outer region of the monofilament. This may further result in an artificial turf fiber with more grass-like properties in terms of both stiffness, surface smoothness, and surface coloration and texture.

[0105] In contrast to alternative approaches in which a marbled color pattern is printed or painted onto the surface of the extruded filament, embodiments of the present method result in a monofilament that includes a marbled color pattern not only on its surface but also within it. If the filament splits, its surface is abraded or otherwise damaged, and the marbled color pattern is not removed because it is not limited to the surface of the monofilament.

[0106] According to an embodiment, the polymer mixture comprises 0.2 to 35% by weight of additional polymer, more preferentially 2 to 10% by weight of additional polymer. According to an embodiment, 3 ~0.920g / cm 3 The amount of "pure" LLDPE having a density in the range of is selected so that the LLDPE polymer, LLDPE masterbatch, optional low density LLDPE, LDPE polymer, other polymers and optional additive and / or filler materials total 100%.

[0107] According to an embodiment, the additional polymer is a polar polymer.

[0108] According to an embodiment, the additional polymer is any one of polyamide, polyethylene terephthalate (PET), and polybutylene terephthalate (PBT).

[0109] According to an embodiment, the marbled pattern of the monofilaments replicates the color pattern of natural grass. For example, one dye may be green and the other dyes may be yellow or pale green. This can be advantageous because it produces an artificial turf fiber that closely replicates the appearance of natural grass.

[0110] According to an embodiment, the first dye is phthalocyanine green at a concentration of 0.001 to 0.3% by weight of the first phase, preferably 0.05 to 0.2% by weight. Preferentially, the first dye has a green or dark green color. According to an embodiment, the second dye is an azo-nickel pigment complex at a concentration of 0.5 to 5% by weight of the second phase, more preferentially 1.5 to 2% by weight. For example, the azo-nickel pigment "BAYPLAST® Gelb 5GN" from LANXESS can be used as the second dye. Preferentially, the second dye has a yellow, light green, or yellow-green color.

[0111] According to an embodiment, the extrusion is carried out at a pressure of 40 to 140 bar, more preferentially 60 to 100 bar. The polymer mixture can be prepared by adding polymer granules to the solid polymer composition, mixing and heating it until all the polymer is melted. For example, the polymer mixture can be heated to reach a temperature of 190 to 260°C, more preferentially 210 to 250°C during extrusion.

[0112] According to an embodiment, the drawing comprises drawing the reheated monofilament according to a draw factor ranging from 1.1 to 8, more preferentially ranging from 3 to 7.

[0113] According to an embodiment, the quenching is carried out in a quenching solution having a temperature between 10 and 60°C, more preferentially between 25°C and 45°C.

[0114] According to an embodiment, in the marbled pattern of the monofilament, the appearance of the two different colors changes preferentially every 50 to 1000 μm, more preferentially every 100 to 700 μm. According to an embodiment, the marbled pattern of the monofilament reproduces the color pattern of natural grass.

[0115] In a further aspect, the present invention relates to an artificial turf comprising artificial turf fibers according to any one of the embodiments and examples described herein.

[0116] According to embodiments, the artificial turf comprises a carrier, for example a carrier fabric made from synthetic and / or natural fibers, whereby the artificial turf fibers are incorporated into the carrier. For example, the fibers may be tufted, knitted, or woven into the carrier.

[0117] According to some embodiments, the artificial turf further comprises a backing, also referred to as a "secondary backing," that surrounds at least a portion of the artificial turf fibers. For example, the secondary backing may be a polyurethane backing or a latex backing. According to embodiments, the backing comprises or consists of a material that is applied in liquid form to at least one surface of the carrier to contact and wet at least a portion of the artificial turf fibers, and then solidifies to form a solid secondary backing.

[0118] In a further aspect, the present invention relates to a method for producing an artificial turf fiber, the method comprising: providing a base polymer; - mixing said base polymer with one or more siloxane-grafted polymers, wherein said one or more siloxane-grafted polymers are polyolefins or polyamides; - extruding the mixture of the base polymer and the polymer grafted with one or more siloxanes into a monofilament to provide the artificial turf fiber, or extruding the mixture of the base polymer and the polymer grafted with one or more siloxanes into a film and cutting the film into slit film strands to provide the artificial turf fiber. For example, one of the extruded monofilaments or slit film strands can be used as an artificial turf fiber directly or after a post-processing step.

[0119] According to an embodiment, the post-treatment step comprises: - quenching the monofilament; - reheating the monofilament; - drawing the reheated monofilaments to form the monofilaments into the artificial turf fibers.

[0120] According to some embodiments, the post-treatment step comprises: - reheating the slit film strand; - stretching the reheated slit film strands into the artificial turf fibers.

[0121] In some embodiments, the base polymer is a blend of two or more immiscible polymers. The first polymer forms beads surrounded by the second polymer. Extrusion stretches the beads of the first polymer into threadlike regions contained in monofilaments or extruded films.

[0122] According to some embodiments, the mixture of base polymer and one or more siloxane-grafted polymers comprises one or more siloxane-grafted polymers in an amount selected such that no more than 0.25% by weight of the artificial turf fibers consists of one or more siloxane-grafted polymers.

[0123] According to some embodiments, the base polymer is a mixture of two or more polymers that are coextruded. For example, the coextruded polymers can be essentially identical but contain different compositions of additives, such as pigments. For example, it can be beneficial to use a coextrusion nozzle shaped so that the extruded monofilament has a core-clad structure, as shown in Figures 1B-1D. This allows for the selective addition of additives, such as pigments, to one of the coextruded polymers that is particularly useful or required. For example, the core and clad polymers can both be the same PE polymer type, but the pigment can be selectively added to the clad polymer rather than the core polymer, since the pigment in the core would not be visible anyway. In other embodiments, the core and clad polymers can be different. For example, the core polymer can comprise or consist of a polymer that is more rigid than the clad polymer.

[0124] In a further aspect, the present invention provides a method of producing artificial turf, comprising the steps of: - incorporating a plurality of artificial turf fibers according to any one of the embodiments and examples described herein into a liquid backing; - solidifying the liquid backing into a film, wherein the film surrounds and thereby mechanically secures at least a portion of the artificial turf fibers, and the solid film acts as an artificial turf backing.

[0125] For example, the liquid backing can be a liquid polyurethane mass or a liquid latex mass.

[0126] Incorporating artificial turf fibers into an artificial turf backing may include incorporating a plurality of artificial turf fibers into a carrier, with a first portion of the fibers exposed on a bottom side of the carrier and a second portion of the fibers exposed on a top side of the carrier, and adding a fluid backing to the bottom side of the carrier such that at least a first portion of the fibers are embedded in the fluid backing. When the fluid backing solidifies into a film, it securely secures the artificial turf fibers in the carrier, at least a first portion of the fibers.

[0127] In a further aspect, the present invention relates to the use of one or more siloxane-grafted polymers as a processing aid to prevent clogging of extrusion nozzles when a base polymer is extruded through the nozzle to form artificial turf fibers or to form a film that is cut into strands for use as artificial turf fibers. The one or more siloxane-grafted polymers are polyolefins or polyamides. In particular, the base polymer may be a mixture of two or more immiscible polymers, whereby one polymer forms beads and is surrounded by the other polymer, thereby forming beads into thread-like regions when the base polymer is pressed through the extrusion nozzle. Additionally or alternatively, the extrusion is co-extrusion of two or more polymers through the same extrusion nozzle.

[0128] In the context of polymer blends with multiple immiscible polymers, the use of one or more siloxane-grafted polymers can be beneficial because it prevents phase separation and clogging of the extrusion nozzle due to large bubbles formed by fused beads of one of the polymers, which can not only clog the extrusion nozzle but also lead to undesirable structural inhomogeneity in the extruded monofilament or breakage of the monofilament during extrusion.

[0129] Similarly, in situations where two or more polymers are coextruded (different types of polymers, such as PE or PA, or the same type of polymer but with different additive compositions, e.g., pigments), the use of one or more siloxane-grafted polymers can be beneficial because it prevents distortion of the desired distribution of the coextruded polymers. For example, it has been observed that siloxane-grafted polymers prevent the accumulation of polymer on the inner walls of the coextrusion nozzle, thereby imparting a desired cross-sectional profile to the interface of the coextruded polymers. For example, a desired polymer distribution profile may be a core-clad structure, created by an inner cylindrical duct made of metal walls, which forces the polymer mass inside the duct (the "core polymer") and the polymer mass outside the inner duct (the "clad polymer") to move in the same direction and in parallel before being extruded.

[0130] The use of immiscible polymers to form thread-like regions and / or the use of coextrusion to create complex polymer distribution patterns are particularly useful in the context of artificial turf fibers, as these fibers must meet multiple requirements regarding their appearance and feel to provide a natural-looking, soft, and elastic fiber that is simultaneously durable and resilient. The complexity of these polymer patterns, especially when combined with complex filigree fiber profiles with undulating and / or concave edges, can cause various problems during extrusion: the extrusion nozzle may become completely or partially clogged, and some polymer fractions or fused polymer beads may adhere to the inner wall of the extrusion nozzle, distorting the desired polymer distribution. This can be prevented by adding one or more siloxane-grafted polymers to at least one or all of the polymers included in the base polymer being extruded.

[0131] As used herein, the term "base polymer" refers to a polymer or polymer mixture that, in its simplest case, can consist of a single polymer, optionally containing one or more additives, such as pigments or flame retardants. However, a "base polymer" can also be a mixture of one or more polymers of different types, such as a mixture of polyethylene and polyamide, or a mixture of HDPE and LDPE, or a mixture of LLDPE and LDPE, optionally containing one or more additives. The polymer mixture can be a single-phase system (such as a mixture of HDPE and LDPE) or a multiphase system (such as a liquid PE polymer containing beads of immiscible PA polymers embedded therein).

[0132] As used herein, the term "coextrusion" refers to the simultaneous extrusion of multiple streams of polymeric material. This type of extrusion utilizes two or more molten polymer masses delivered at a steady volumetric throughput to a single extrusion head (die), which extrudes the material in the desired form. The distribution of the coextruded polymer masses in the extruded monofilament is controlled by the relative speeds and amounts of the polymer mass streams and the size and shape of the extrusion nozzle. Often, a single polymer cannot meet all the requirements of an application. Composite extrusion allows blended materials to be extruded, allowing for the appropriate placement of materials with different properties such as composition (additive content), strength, stiffness, and wear resistance.

[0133] As used herein, the term "low density polyethylene" (LDPE) refers to polyethylene having a density of 0.910-0.940 g / cm 3 According to an embodiment, the base polymer is or includes LDPE having a density range within the specified subranges above.

[0134] The term "linear low-density polyethylene" (LLDPE) as used herein refers to a substantially linear polymer (polyethylene) with a significant number of short branches. LLDPE is structurally different from conventional LDPE due to the absence of long-chain branching. The linearity of LLDPE results from the different manufacturing processes for LLDPE and LDPE. Generally, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene with α-olefins. [Brief explanation of the drawings]

[0135] In the following, embodiments of the invention will be described in more detail, by way of example only, with reference to the drawings, in which:

[0136] [Figure 1A] 1 illustrates various artificial turf fibers and their cross-sectional profiles. [Figure 1B] 1 illustrates various artificial turf fibers and their cross-sectional profiles. [Figure 1C] 1 illustrates various artificial turf fibers and their cross-sectional profiles. [Figure 1D] 1 illustrates various artificial turf fibers and their cross-sectional profiles. [Figure 2] 1 is a flow chart of a method for producing artificial turf fibers. [Figure 3] FIG. 1 is a diagram of a siloxane-grafted polymer. [Figure 4] FIG. 1 is a diagram of a base polymer comprising a polymer grafted with one or more siloxanes and other additives. [Figure 5] FIG. 1 is a diagram of a polymer mixture comprising two polymers, a compatibilizer, and one or more siloxane-grafted polymers. [Figure 6] FIG. 1 is a diagram of a process for extruding a polymer monofilament through an extrusion nozzle. [Figure 7] 1 is a diagram of artificial turf and its production. [Figure 8] FIG. 1 shows a cross section through a region within a cylindrical extrusion nozzle. [Figure 9]FIG. 9 shows a cross section of a granular polymer mixture 900 including LLDPE and LDPE according to one embodiment. [Figure 10] FIG. 1 shows a co-extrusion nozzle. [Figure 11] FIG. 1 is a block diagram of a system for synthesizing maleic acid grafted polyolefins or polyamides. DETAILED DESCRIPTION OF THE INVENTION

[0137] Like numbered elements in these figures are either equivalent elements or perform the same function. An element that is previously described is not necessarily described in a later figure if the function is equivalent.

[0138] Figures 1A-D show various artificial turf fibers and their cross-sectional profiles.

[0139] Artificial turf fibres according to embodiments of the present invention may vary greatly in terms of their composition and / or in terms of their internal structure and / or in terms of their cross-sectional profile.

[0140] For example, artificial turf fibers may be composed solely or primarily of a single polymer, such as the same type of polyethylene, or may be composed of a homogeneous single-phase blend of different polymers (e.g., LLDP and HDPE, or LLDP and LDPE), or may be composed of a combination of several different polymers forming a single-phase or multi-phase system.

[0141] For example, the artificial turf fiber 100 shown in FIG. 1A may have a cross-sectional profile 102 that is circular or oval.

[0142] According to another example, the artificial turf fiber 120 may include one or more protrusions, as shown, for example, in FIG. 1B. The artificial turf fiber 120 includes two protrusions 104. The protrusions may include an angle of 100 to 180 degrees. In the non-limiting example shown, the protrusions face in opposite directions. The fiber 120 has a rounded bulge in the center and two protrusions 104 with rounded tips. The core 103 and cladding 110 may be joined together by a contact layer 108 in which the core polymer and cladding polymer are mixed.

[0143] As seen in FIG. 1B, the fiber core includes thread-like regions 106, which may include a first polymer, e.g., a polar polymer such as polyamide. The thread-like regions are formed in an extrusion process from beads of the first polymer surrounded by a compatibilizer and embedded in a second polymer, e.g., a non-polar polymer such as polyethylene. The polymer in the core surrounded by thread-like regions 106, and the cladding polymer, may be a non-polar polymer, e.g., polyethylene, also referred to herein as the "second polymer." However, it is also possible for the core polymer and cladding polymer to be different, e.g., polyethylene in the cladding and polypropylene in the core.

[0144] Preferably, the thread polymer or "first polymer" in the thread region 106 will be no more than 30% by weight of the core, so that the cohesion provided by the contact layer 108 remains equal to or stronger than a conventional tri-component artificial turf fiber having a compatibilizing layer joining the core and cladding, even when the thread polymer and cladding polymer are not miscible with each other. The contact layer 108 may extend radially up to 50 percent of the minimum thickness of the cladding 110 in all directions extending radially from the core 103.

[0145] FIG. 1C shows a cross section of an artificial turf fiber 130 having a core-clad structure and two protrusions 104. In the example shown, the two protrusions encircle an angle of approximately 135 degrees toward the wavy side 112 of the profile. Both protrusions have a radial extension of approximately three times the thickness of the ridge 114. The profile extends over the entire thickness t between the front central ridge 114 and the rear tip of the protrusion. The distance between the two tips is the entire width w of the fiber. Both protrusions have a profile with one straight side 116 and, opposite the straight side 116, one wavy side 112 with four notches along a straight baseline. Considering the axial extension of the fiber, this profile corresponds to a protrusion with one flat surface and one grooved surface.

[0146] For illustrative purposes only, assuming an exemplary overall profile width w=1.35 mm and overall thickness t=0.45 mm, the profile of FIG. 1C will have a width of 0.216 mm. 2 The cross-sectional area is 0.92g / mm 2 At an exemplary average density of 1000 dtex, this corresponds to a yarn weight of about 2000 dtex.

[0147] FIG. 1D shows a cross section of an artificial turf fiber 140 having a core-clad structure and two protrusions 104. The fiber shown in FIG. 1C is similar to the fiber shown in FIG. 1A, with the difference being that the straight side 116 of the profile is replaced by a concave side 118, which corresponds to a protrusion with one concave surface and one grooved surface. The curvature is designed so that the thickness of the protrusions (measured between the concave side 118 and the baseline of the wavy side 112) gradually decreases towards their respective tips. In comparison with the non-limiting example above, with an overall width w=1.35 mm and an overall thickness t=0.45 mm as described above, the profile of FIG. 1D has a thickness of 0.180 mm. 2 The cross-sectional area is 0.92g / mm 2At an assumed average density of 0.05, this corresponds to a yarn weight of about 1650 dtex. The fiber with the concave profile of Figure 1D has a weight reduction of about 17% compared to the fiber with the straight profile of Figure 1C. Because the concave profile has a slightly larger circumference than the straight profile, the fiber with the concave profile also has an increased surface-to-mass ratio compared to the fiber with the straight profile.

[0148] Various other types and configurations of artificial turf fibers are possible. The structures shown herein having a core-clad structure can also be formed as fibers containing only a single homogenous mass of a single polymer or homogenous polymer blend. It is also possible for a core-clad structure to be present, but for the core of the structure to not include a beaded region.

[0149] However, based on some of the examples shown here, it is clear that some profiles and shapes of artificial turf fibers are very delicate and therefore susceptible to shear forces at the opening of the extrusion head. If the velocities of the polymer mass at the core and periphery (e.g., especially at the tips of the protrusions) are too different due to excessive viscosity or excessive adhesion of the polymer mass to the wall of the extrusion head, such filigree profiles may clog the extrusion nozzle, blur or cause defects in the profile, or even tear the monofilament during extrusion. By adding one or more siloxane-grafted additive polyolefins or one or more siloxane-grafted polyamides to the polymer, these drawbacks can be avoided and even very delicate synthetic fiber profiles can be formed.

[0150] When a core-clad structure is present, it is also possible to add one or more siloxane-grafted polymers only to the clad polymer and not to the core polymer, since the risk of polymer mass adhering to the die walls is particularly high.

[0151] Therefore, the use of polymers grafted with one or more siloxanes makes it possible to produce artificial turf fibers with very fine profiles, thereby more closely mimicking natural turf in its visual appearance and physical properties. The use of polymers grafted with one or more siloxanes can make it possible to produce high-quality artificial turf fibers that faithfully replicate the properties of natural turf (e.g., appearance, wet behavior, flexibility, etc.).

[0152] 2 is a flowchart illustrating an example of a method for producing artificial turf fibers. First, in step 202, a base polymer is provided. For example, the base polymer can include or consist of a molten polymer or a polymer blend. The base polymer may include one or more additives, such as flame retardants, pigments, UV stabilizers, nucleating agents, delustering agents, antioxidants, or fillers.

[0153] Next, in step 204, one or more siloxane-grafted polymers (polyolefins or polyamides grafted with one or more siloxanes) are mixed with the base polymer. For example, mixing step 202 may be performed in an extruder by uniformly mixing one or more siloxane-grafted polymers with the molten base polymer. Mixing may be performed using one or more agitators. In some implementation variations, it is also possible to add one or more siloxane-grafted polymers to the base polymer before it enters the extruder, for example, while the base polymer is still in solid form. For example, the base polymer may have the form of polymer granules of a single type of polymer or two or more different types of polymers. Optionally, the base polymer may include a polymer granule fraction called a "masterbatch" that contains pigments and / or additional additives.

[0154] In some implementation variations, the base polymer is a polymer mixture having two or more distinct phases. For example, the base polymer may be a polymer mixture as shown in FIG.

[0155] In the next step 206, the mixture of base polymer and one or more siloxane-grafted polymers is extruded into monofilaments.

[0156] According to a preferred embodiment, the extruded monofilament undergoes several post-processing steps. For example, the monofilament is quenched, i.e., rapidly cooled, for example, by immersing the monofilament in cold water. The monofilament can then be reheated and stretched to form the monofilament into an artificial turf fiber. If the base polymer is a multiphase polymer mixture in which a first polymer forms beads within a second polymer, the stretching step transforms the polymer beads into threadlike regions, which provides additional rigidity to the fiber.

[0157] According to another embodiment, the polymer mixture is not extruded into monofilaments, but rather extruded into a film in step 205. The film is sliced into a plurality of thin polymer stripes in step 207 and then used as artificial turf fibers or further processed for use as artificial turf fibers. This approach is also known as the "slit film" manufacturing technique.

[0158] Next, in step 208, the extruded monofilament or the polymer slits (also referred to herein as "monofilaments") obtained in the slit film yarn manufacturing process are used as artificial turf fibers. For example, the monofilament or a bundle of monofilaments can be incorporated into a carrier to form artificial turf. Additional steps may be performed on the monofilament to form the artificial turf fiber. For example, the monofilament can be spun or woven into a yarn with desired properties, and this yarn can be incorporated into the carrier instead of the monofilament. This incorporation can be done, for example, by tufting or weaving the artificial turf fiber into an artificial turf backing. Then, in a further optional step, the incorporated artificial turf fiber can be fixed in the desired position in the carrier by adding a secondary backing on at least one side of the carrier. For example, the secondary backing can be polyurethane or latex. The relatively low concentration of the polymer grafted with one or more siloxanes can ensure that the surface roughness of the fiber is high enough to allow the secondary backing to firmly secure the fiber.

[0159] 3 is a diagram of a polymer grafted with one or more siloxanes 300. Grafting is a statistical process. Preferably, the polymer grafted with one or more siloxanes has multiple siloxanes 302 grafted to a polymer backbone 304.

[0160] 4 is a diagram of a base polymer 400 including a polymer grafted with one or more siloxanes 404, and other additives 406 dispersed in the base polymer. The siloxane-grafted polymers 404 may be dispersed in the base polymer and mixed with the base polymer by a stirrer or screw. The base polymer includes at least one polymer 402, such as polyethylene. The other additives 406 may include nucleating agents, such as phthalocyanine green or phthalocyanine blue, and / or UV stabilizers.

[0161] FIG. 5 shows a base polymer 500 that is a polymer blend. The polymer blend includes a first polymer 502, e.g., a polar polymer such as polyamide, and a second polymer 506. The second polymer may be a non-polar polymer such as polyethylene. The polymer blend may further include a compatibilizer 504. The first and second polymers are immiscible. In other examples, there may be an additional polymer, such as a third, fourth, or even fifth polymer, that is also immiscible with the second polymer. There may also be an additional compatibilizer used in combination with either the first polymer or the additional third, fourth, or fifth polymer. The first polymer forms polymer beads surrounded by the compatibilizer. The polymer beads may be formed by an additional polymer (e.g., a third, fourth, etc. polymer) that is not miscible with the second polymer and is surrounded by the compatibilizer 504 or a different compatibilizer.

[0162] The polymer beads are surrounded by a compatibilizer and are within or mixed into a second polymer.

[0163] The base polymer 500 may also include other additives such as additives for coloring, for providing flame or UV resistance, or for improving the flow properties of the polymer blend. In particular, the base polymer 500 includes a polyolefin or polyamide grafted with one or more siloxanes 508.

[0164] FIG. 6 is a diagram of a process for extruding a base polymer into a monofilament 606 that can be used as an artificial turf fiber. A quantity of base polymer in the form of a polymer mixture 600 is shown. Within the polymer mixture 600 are numerous polymer beads 610. The polymer beads 610 may be made from one or more polymers that are not miscible with the second polymer 602 and are separated from the second polymer 602 by a compatibilizer (not shown). A screw, piston, or other device is used to force the polymer mixture 600 through holes 603 in a plate 604. This extrudes the polymer mixture 600 into the monofilament 606 and stretches the polymer beads 610 into the thread-like region 106. The second polymer 602 and the polymer beads 610 are extruded together. In some instances, the second polymer 602 is less viscous than the polymer beads 610, which tend to concentrate at the center of the monofilament 606. This may result in a concentration of thread-like regions 106 in the core region of the monofilament 606, which may result in desirable properties in the final artificial turf fiber.

[0165] The one or more siloxane-grafted polymers 608 can be uniformly dispersed throughout the base polymer 600, reducing the viscosity and adhesiveness of the base polymer. In examples where the base polymer includes multiple immiscible polymers, the one or more siloxane-grafted polymers can be primarily or solely contained in one of the polymers with the highest occupancy of the base polymer, e.g., a second polymer 602 in which other immiscible polymers are embedded as polymer beads 610. This can ensure that the polymer beads 610 do not fuse and separate into polymer compartments in the extrusion nozzle, which could clog the nozzle or generate shear forces that could tear the monofilament 606. These shear forces can result from the first polymer adhering to the metal walls of the opening 603 in the plate 604 during extrusion.

[0166] It should be noted that Figure 6 does not depict the sizes of the polymer beads 610 and the one or more siloxane-grafted polymers 608 to scale. According to examples, the additives are dispersed in the base polymer in a much finer particulate manner, e.g., at the level of individual molecules or molecular aggregates, while the polymer beads in some examples typically have a size of about 0.1 to 3 micrometers, preferably 1 to 2 micrometers, in diameter. In other examples, the polymer beads are larger. They may have a size, e.g., up to 50 micrometers in diameter.

[0167] In some embodiments, the polymer beads contain crystalline and amorphous portions. The polymer mixture is heated during the extrusion process, and portions of the first polymer and portions of the second polymer may have a more amorphous or more crystalline structure in various regions. Stretching the polymer beads into threadlike regions can increase the size of the crystalline portions relative to the amorphous portions in the first polymer. This can result in, for example, the first polymer becoming stiffer than if it had an amorphous structure. This can result in artificial turf with greater stiffness and the ability to bounce back when pressed down. Stretching the monofilament can also, in some cases, cause the second polymer or other additional polymers to become more crystalline in larger portions of their structure.

[0168] In this particular example, the first polymer is a polyamide and the second polymer is polyethylene. Stretching a polyamide increases the crystalline regions, making the polyamide more rigid. This is also true for other plastic polymers.

[0169] In another embodiment, the step 600 of providing a base polymer includes a step of producing a polymer mixture to be used as the base polymer. The step of producing the polymer mixture includes mixing a first polymer with a compatibilizer to form a first mixture. The step of producing the polymer mixture further includes heating the first mixture. Then, extruding the first mixture into granules to create granules. The step of producing the polymer mixture further includes mixing the first mixture with a second polymer. The step of producing the polymer mixture further includes heating the granulated first mixture with the second polymer to form a polymer mixture. Then, for example, during or after heating, one or more siloxane-grafted polymers are added to the polymer mixture and mixed with the polymer mixture. For example, adding one or more siloxane-grafted polymers to the polymer mixture may be performed in an extruder. This particular method of making the polymer blend can be advantageous because it allows for very precise control over how the first polymer and compatibilizer are distributed within the second polymer, and allows for the one or more siloxane-grafted polymers to be uniformly mixed into the resulting polymer blend before it is extruded. For example, the size or shape of the extruded first blend can determine the size of the polymer beads in the polymer blend.

[0170] In the method for preparing the above-mentioned polymer mixture, for example, the so-called single-screw extrusion method can be used. Alternatively, the polymer mixture can be prepared by combining all of its constituent components at once without an intermediate extrusion step. For example, the first polymer, the second polymer, the compatibilizer, and optionally one or more siloxane-grafted polymers can all be added together simultaneously or subsequently while the mixture is continuously stirred. Other components, such as additional polymers or other additives, can also be added simultaneously and / or continuously during constant stirring. However, it is also possible to add one or more siloxane-grafted polymers later, for example, after the polymer mixture has been transferred to an extruder. The amount of mixing of the polymer mixture can be increased, for example, by using a twin-screw feed for extrusion. In this case, the desired distribution of polymer beads can be achieved by using an appropriate speed or amount of mixing.

[0171] In some exemplary embodiments, the polymer mixture is at least a four-phase system. The polymer mixture includes at least a third polymer. The third polymer is immiscible with the second polymer. The third polymer further forms polymer beads surrounded by a compatibilizer within the second polymer. In some examples, creating the polymer mixture includes forming a first mixture by mixing the first polymer and the third polymer with a compatibilizer. Producing the polymer mixture further includes heating the first mixture. Producing the polymer mixture includes first extruding the first mixture. Producing the polymer mixture further includes granulating the extruded first mixture. Producing the polymer mixture further includes mixing the first mixture with a second polymer. Producing the polymer mixture further includes heating the first mixture with the second polymer to form a polymer mixture and uniformly mixing a siloxane-grafted polymer into the polymer mixture. This method can provide a precise means of creating polymer mixtures using two different polymers and controlling the size and distribution of the polymer beads. Alternatively, a first polymer can be used to make granules with a compatibilizer, separately from making a third polymer with the same or a different compatibilizer, and the granules can then be mixed with a second polymer to make a polymer mixture.

[0172] Alternatively, the first polymer, the second polymer, the third polymer, the compatibilizer, and optionally the siloxane-grafted polymer can all be added together at the same time, and then mixed more vigorously to create the polymer mixture. For example, a twin-screw feeder can be used in the extruder. In some examples, the siloxane-grafted polymer is added later, for example, to the polymer mixture already transferred to the extruder.

[0173] In some examples, the third polymer is a polar polymer, such as a polyamide. In some examples, the third polymer is polyethylene terephthalate, also commonly abbreviated as PET. In some examples, the third polymer is polybutylene terephthalate, also commonly abbreviated as PBT.

[0174] According to some examples, the polymer blend comprises 1% to 30% by weight of the first polymer and the third polymer combined, in which case the remainder of the weight may be made up of components such as the second polymer, the compatibilizer, and any other additional additives added to the polymer blend.

[0175] In some examples, the thread-like region has a diameter of less than 20 micrometers. In some examples, the thread-like region has a diameter of less than 10 micrometers. In some examples, the thread-like region has a diameter of 1 to 3 micrometers.

[0176] In some examples, the artificial turf fibers extend beyond the artificial turf substrate a predetermined length, and the thread regions have a length that is less than half of the predetermined length. In some examples, the thread regions have a length that is less than 2 mm.

[0177] According to some examples, the polymer blend comprises 1-20 wt.% of the first polymer and the third polymer combined, again in this example the remainder of the weight of the polymer blend may be made up of the second polymer, the compatibilizer, and any other additional additives.

[0178] According to some examples, the polymer blend comprises 5% to 10% by weight of the first polymer and the third polymer combined, again in this example the remainder of the weight of the polymer blend may be made up of the second polymer, the compatibilizer, and any other additional additives.

[0179] According to some examples, the polymer mixture includes 1% to 30% by weight of the first polymer, in which case the remainder of the weight may be made up of, for example, the second polymer, the compatibilizer, and any other additional additives.

[0180] According to some examples, the polymer blend comprises 1% to 20% by weight of the first polymer, in which case the remainder of the weight may be made up of the second polymer, the compatibilizer, and any other additional additives mixed into the polymer blend.

[0181] According to some examples, the polymer blend comprises 5% to 10% by weight of the first polymer, with the balance of the weight being made up of the second polymer, the compatibilizer, and any other additional additives blended into the polymer blend.

[0182] According to some examples, the first polymer is a polyamide or polyethylene terephthalate (PET) or polybutylene terephthalate (PBT).

[0183] According to some examples, the second polymer is a non-polar polymer, such as polyethylene or polypropylene, or a mixture of the aforementioned polymers.

[0184] According to some examples, the polymer blend comprises 80-90% by weight of the second polymer, in which case the balance of the weight may be made up of the first polymer, optionally the second polymer if present in the polymer blend, the compatibilizer, and any other chemicals or additives added to the polymer blend.

[0185] According to some examples, the polymer mixture further comprises any one of the following: waxes, matting agents, UV stabilizers, flame retardants, antioxidants, pigments, and combinations thereof. These listed additional ingredients can be added to the polymer mixture to impart other desirable properties to the artificial turf fibers, such as flame retardancy, a green color so that the artificial turf resembles grass more, and greater stability in sunlight.

[0186] Artificial turf containing fibers made from one or more monofilaments containing the aforementioned threadlike regions may have the advantage of being extremely durable because the threadlike regions are embedded within a second polymer via a compatibilizer. Therefore, they do not have the ability to delaminate. Having a second polymer surrounding a first polymer can provide a firm artificial turf with a soft, natural feel. Artificial turf containing these threadlike regions differs from coextruded artificial turf. In coextrusion, a core, typically 50-60 micrometers in diameter, may be surrounded by an outer cover or sheath material with a diameter of approximately 200-300 micrometers. This artificial turf contains multiple threadlike regions of the first polymer. The threadlike regions may not be continuous along the entire length of the monofilament. Artificial turf may also have properties or characteristics provided by any of the aforementioned process steps. Nevertheless, a combination of coextrusion and threadlike regions is possible, as shown in Figure 1B.

[0187] The addition of one or more siloxane-grafted polyolefins or one or more siloxane-grafted polyamides can be very useful when fibers are made by co-extruding two or more different polymers, for example to achieve a core-shell structure, because the one or more siloxane-grafted polymers prevent distortion of the desired polymer pattern (e.g., core-shell pattern) caused by one of the co-extruded polymers adhering too strongly to the walls of the extrusion nozzle.

[0188] FIG. 7 is a diagram of artificial turf 700 and its manufacture. After the base polymer is extruded into monofilaments, the monofilaments may be further processed to convert one or more monofilaments into artificial turf fibers. The artificial turf fibers 701 are incorporated into a carrier 704, also referred to as a "primary backing," such as a carrier fabric. In some examples, the carrier 704 is a woven fabric or woven mat.

[0189] Incorporation of the artificial turf fibers into the artificial turf substrate may be performed, for example, by tufting the artificial turf fibers into the artificial turf substrate, as shown in the left portion of Figure 7. This forms loops that are cut by one or more knives 708. This produces artificial turf 700, which includes a plurality of synthetic fibers 701 incorporated into a carrier 704. Optionally, a further secondary backing, such as a latex- or polyurethane-based backing, may be applied to the underside of the artificial turf to securely fasten the tuft loops 706 on the underside of the carrier and the fibers contained therein to the carrier. The incorporated artificial turf fibers protrude a specified height 702 above the top side of the carrier.

[0190] According to some examples, integrating the artificial turf fibers in the carrier includes weaving, bundling, or spinning multiple monofilaments together to create the artificial turf fibers. The incorporation of the artificial turf fibers into the artificial turf substrate can alternatively be performed by weaving the artificial turf fibers into the artificial turf substrate (or fiber mat), for example, during the production of an artificial turf carpet. This technique for producing artificial turf is known from U.S. Patent Application Publication No. 20120125474.

[0191] In some examples, the artificial turf fiber is not a single monofilament, but a combination of several fibers. In some examples, the artificial turf fiber is a yarn. In some examples, multiple stretched monofilaments are bundled together to create the artificial turf fiber. Multiple monofilaments, for example, 4 to 8, can be formed or finished into a yarn.

[0192] Figure 8 shows a cross section through regions within a funnel-shaped extrusion nozzle. In a first region 802, the polymers of the liquefied polymer mixture are mostly amorphous, i.e., there are few or no crystalline regions, and the polymer molecules do not exhibit a preferred orientation in one dimension. In a second region 804, corresponding to a region of increased shear, the polymer molecules are sheared and pulled at least partially toward the nozzle opening 810. In a region 806, corresponding to high shear, the LLDPE and partially LDPE molecules are also at least partially unraveled and oriented, forming crystalline portions 808. However, according to a preferred embodiment, the majority of the crystalline portions are generated late in the drawing process.

[0193] The use of an LLDPE-LDPE blend in combination with one or more siloxane-grafted polymers in accordance with embodiments of the present invention can be beneficial because the additive helps prevent the formation of crystalline moieties in region 808, thereby preventing fiber breakage and preventing delamination and splicing of the artificial turf fiber during use. By adding an appropriate amount of LDPE, particularly LDPE of a specific density, to the polymer blend, splicing can be prevented, even in fibers that have been stretched during manufacturing. While not wishing to be bound by any theory, Applicant believes that LDPE ensures a sufficient degree of entanglement of the polymer side chains, and that the one or more siloxane-grafted polymers support this entanglement by preventing the formation of crystalline moieties in regions 804 and 808.

[0194] 9 shows a cross section of a granular polymer mixture 900 including LLDPE and LDPE according to one embodiment. The polymer mixture may include the following components, for example in the form of polymer granules that are subsequently melted: -Density 0.919g / cm 3 and a "pure" first LLDPE polymer 908 in an amount of 73% by weight of the polymer blend. The first LLDPE polymer preferably does not contain any additives. -Density 0.919g / cm 3and a "masterbatch" 902 comprising the first LLDPE polymer in an amount of 10% by weight of the polymer mixture. The masterbatch may include additives. -Density 0.920g / cm 3 and LDPE polymer 904 in an amount of 7% by weight of the polymer mixture. -Density 0.916g / cm 3 and a second low density LLDPE polymer 906 in an amount of 10% by weight of the polymer mixture.

[0195] Depending on the embodiment, the amounts of filler material, masterbatch, LDPE, and first and second LLDPE polymers may vary. Preferentially, the amount of additive-free first LLDPE polymer 902 is adapted in this case so that all components of the polymer mixture add up to 100%.

[0196] In the illustrated example, the LLDPE polymer in fraction 908 and in masterbatch 902, as well as the additives contained in the master mix, may comprise 83% by weight of polymer mixture 900. In other embodiments (not shown), polymer mixture 900 may contain up to 39% filler material. If the polymer mixture contains 1% LDPE polymer and 99% LLDPE polymer (no fillers or additives), a 1:99 LDPE / LLDPE weight ratio is used. If the polymer mixture contains 15% LDPE polymer and 60% LLDPE polymer (large amounts of fillers and additives may be used), a 15:60 LDPE / LLDPE weight ratio is used. Preferentially, the LDPE / LLDPE weight ratio is between 5:95 and 8:60, i.e., between 5.3% and 13.3%.

[0197] In the illustrated example, 0.05% by weight of the polymer mixture consists of one or more siloxane-grafted polymers.

[0198] In some examples, polymer components 902, 904, 906, 908 together form a first liquid phase (corresponding to a "second polymer") that may further include an additional polymer, also referred to as a "first polymer," e.g., PA, that may form a separate phase that forms beads within the first phase. In this case, the amount of the first LLDPE is reduced according to the amount of the additional polymer.

[0199] FIG. 10 shows a co-extrusion nozzle 920 for producing artificial turf fibers with a core-clad polymer distribution pattern.

[0200] The nozzle includes a bonding path 940 located upstream of the coextrusion opening 938. This mechanism includes a cavity 936 that receives the free end of the capillary tube 935. Opposite the inserted capillary tube 935, the cavity 936 terminates at the coextrusion opening 938. A gap between the capillary tube 935 and the wall of the hole 936 hydraulically connects the hole to the second channel system 934. The capillary tube 935 is hydraulically connected to the first channel system 932 and is not fully inserted into the hole 936 such that a portion 940 of the hole 936 is hydraulically connected to both the first channel system 932 and the second channel system 934. This cavity 936 defines the bonding path 940 of the illustrated coextrusion setup. The bonding path 940 extends from the capillary tube 935 to the extrusion opening 938, as indicated by the dotted line.

[0201] During the coextrusion operation, capillary tube 935 receives the molten core polymer component from first channel system 932, and cavity 936 receives the molten cladding polymer component from second channel system 934. The transport direction of each of the polymer components is indicated by an arrow. The two polymer components flow separately from each other until they meet at a converging path 940. The two joined polymer components pass through joining path 940, which narrows toward the cross section of coextrusion opening 938, and exit coextrusion opening 938 as a bicomponent monofilament.

[0202] When the core and cladding are joined together with a contact layer containing a mixture of the core polymer blend and the cladding polymer component, the dimensions of the joining path are appropriately selected to form a stable contact layer of uniform thickness. In one example, the contact layer is formed within an axial length of the joining path that is 3 to 7 times the diameter of the liquid core polymer blend at the upstream end of the joining path. In a more specific example, the diameter of the liquid core polymer blend at the upstream end of the joining path is 0.5 to 1.5 mm, the axial length of the joining path is 1.5 to 10.5 mm, and the molten core polymer blend is mixed with the cladding polymer component in a contact layer having a radial thickness of 10 to 150 μm.

[0203] FIG. 11 shows a block diagram of a system for synthesizing maleic acid-grafted polyolefin (PO-g-MA). The PO-g-MA can then be used in further processing steps to synthesize polyolefins grafted with one or more siloxanes (PO-g-Si). A twin-screw extruder 956 including a die head 960 is shown. The extruder includes a first opening 950 through which polyolefin (e.g., PP, EVA (ethylene-vinyl acetate copolymer), and / or LLDPE), a reactive monomer such as maleic anhydride (MAH), and an initiator (peroxide) are fed into the extruder. Alternatively, the extruder may include one or more separate openings 952 for adding the MAH and initiator separately from the polymer. The polyolefin is typically provided in the form of granules or pellets. The reactive monomer may be provided, for example, as a vinyl monomer such as maleic anhydride (MA). Instead of MA, glycidyl methacrylate (GMA) may be used. A vacuum pump 958 is configured to transport the mixture of polymer, reactive monomer, and peroxide to a die head 960. The mixture of polyolefin, initiator, and reactive monomer is melt-extruded to produce MA-grafted polyolefin (PO-g-MA). According to some examples, as a result of this synthesis step, 0.1% to 0.5% of the polyolefin's monomers (e.g., ethylene monomers in the case of polyethylene) are functionalized with MA, thereby providing functional groups that allow for the covalent attachment of siloxanes to the polyolefin backbone in subsequent synthesis steps. This process is also referred to as "reactive extrusion," since a free-radical initiator attaches functional groups to the polyolefin chain by linking the reactive monomer to the polyolefin chain. For example, the PO-g-MA can be a maleic anhydride-grafted polyolefin having a weight fraction of the acid anhydride ranging from 0.01 to 10%, particularly 0.15 to 10%, based on the total molecule.

[0204] In some examples, the PO-g-MA is MA-HDPE. In other examples, the PO-g-MA is MA-LLDPE, MA-PP, or MA-PA. In each of these examples, the Ma content is preferably in the range of 0.5% to 2% by weight of the PO-g-MA molecule, particularly about 1.0% by weight.

[0205] In the second synthesis step (not shown), PO-g-MA is stirred with a hydroxy-functionalized siloxane in a batch reactor at 180 °C to produce polyolefin (PO) grafted with one or more siloxanes (PO-g-Si). For example, PO-g-Si can be synthesized by reacting an anhydride-containing polyolefin in a solvent with a hydroxy-functional linear organically modified siloxane. For example, the siloxane can be a polyester-modified siloxane, such as an α,ω-dihydroxy polyester siloxane. The reaction is initiated at elevated temperatures of 165–195 °C under vigorous stirring. This allows one or more organopolysiloxanes to be attached to the polyolefin backbone via ester bonds. Condensation between the hydroxyl and anhydride groups results in permanent chemical bonding of the siloxane chain to the polymer matrix. As an alternative to the solvent-based approach, PO-g-Si can also be prepared under shear, for example, during incorporation into a polymer on an extruder. Instead of the hydroxy-functionalized siloxanes, other types of chemically equivalent siloxanes may be used, such as amino-functionalized siloxanes.

[0206] Siloxane-grafted polyamides can be synthesized similarly using, for example, anhydride-group-containing polyamines.

[0207] According to some implementation variations, polyolefin-grafted siloxanes are synthesized as described in European Patent Application EP 1211277 B1, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0208] 100 Artificial Grass Fiber 102 Circular or elliptical cross-section fiber profiles 103 cores 104 Protrusion 106 filamentous region 110 Clad 112 Wavy side 114 Core-clad interface 115 Bulge 116 Straight Side 118 concave side 120 Artificial Grass Fiber 130 Artificial turf fiber, cross section 140 Cross section of artificial turf fiber 202-208 Process 300 Siloxane-grafted polyolefin 302 Siloxane 304 Polyolefin 400 Polymer Mixture 402 Base Polymer 404 Polyolefins grafted with one or more siloxanes 406 Further Additives 408 Polymer Beads 500 Polymer Mixture 502 First Polymer 504 Compatibilizer 506 Second Polymer 508 Polyolefins grafted with one or more siloxanes 600 Polymer Mixture 602 Second Polymer 603 holes 604 Plate 606 Monofilament 608 Polyolefins grafted with one or more siloxanes 610 First polymer (beads) 700 artificial grass 701 Artificial turf fiber 702 Fiber Height 704 Carrier 706 Tufted loop on the underside of the carrier 708 Knife cut fiber loop on top of carrier 802 Regions with mainly amorphous state 804 Regions of enhanced shear in polymer mixtures 806 High shear area 808 Crystal part 810 Nozzle opening 900 Polymer Mixture 902 Masterbatch LLDPE Fraction 904 LDPE polymer fraction 906 Second LLDPE polymer fraction 908 (primary / main) LLDPE fraction 920 Co-extrusion nozzle 932 First Channel System 934 Second Channel System 935 Capillary 936 Cavity 938 Co-extrusion opening 940 Conjugation Pathways 950 First opening 952 Second Opening 956 Twin Screw Extruder 958 Vacuum Pump 960 die head

Claims

1. 1. An artificial turf fiber comprising one or more siloxane-grafted polymers, wherein the polymer is a polyolefin or a polyamide.

2. 10. The artificial turf fiber of claim 1, wherein the artificial turf fiber is free of halogen compounds.

3. 10. The artificial turf fiber of claim 1, wherein the artificial turf fiber is free of free siloxanes.

4. 2. The artificial turf fiber of claim 1, wherein the polyolefin is polyethylene or polypropylene.

5. 2. The artificial turf fiber of claim 1, wherein no more than 0.25% by weight of the artificial turf fiber consists of the polymer grafted with the one or more siloxanes, in particular at least 0.01% by weight of the artificial turf fiber, in particular 0.01% to 0.25% by weight of the artificial turf fiber, in particular 0.01% to 0.09% by weight of the artificial turf fiber, in particular 0.02 to 0.03% by weight of the artificial turf fiber consists of the polymer grafted with the one or more siloxanes.

6. 2. The artificial turf fiber according to claim 1, wherein the molecular weight of the polymer grafted with one or more siloxanes is greater than 500 Daltons, in particular at least 50% of the molecules of the polymer grafted with one or more siloxanes have a molecular weight of at least 2000 Daltons, in particular at least 10,000 Daltons, in particular at least 100,000 Daltons.

7. 2. The artificial turf fiber of claim 1, wherein the polymer grafted with the one or more siloxanes is a graft copolymer in which multiple siloxane side blocks are grafted onto the polyolefin backbone.

8. 10. The artificial turf fiber of claim 1, wherein in the polymer grafted with one or more siloxanes, the polyolefin:siloxane ratio is selected such that the polymer grafted with one or more siloxanes is solid or has a waxy consistency at room temperature.

9. 10. The artificial turf fiber of claim 1, comprising two or more protrusions extending in different directions from a center of the artificial turf fiber.

10. 10. The artificial turf fiber of claim 9, wherein the profile of at least one of the protrusions comprises a concave side and / or a wavy section that extends over at least 60% of one side of at least one protrusion.

11. 10. The artificial turf fiber of claim 1, wherein the artificial turf fiber comprises a base polymer, and the one or more siloxane-grafted polymers are dispersed in the base polymer.

12. 12. The artificial turf fiber of claim 11, wherein a major portion of the base polymer is selected from the group consisting of polyethylene, polypropylene, polyamide, polyethylene terephthalate (PET), and polybutylene terephthalate (PBT).

13. 12. The artificial turf fiber of claim 11, wherein the base polymer comprises a first polymer, a second polymer, and a compatibilizer, wherein the first polymer and the second polymer are immiscible, and the first polymer forms thread-like regions within the second polymer surrounded by the compatibilizer.

14. 14. The artificial turf fiber of claim 13, wherein the first polymer is any one of polyamide, polyethylene terephthalate (PET), and polybutylene terephthalate (PBT), and / or the second polymer is any one of polyethylene, polypropylene, and mixtures thereof.

15. 14. The artificial turf fiber of claim 13, wherein the first polymer is a polar polymer and the second polymer is a non-polar polymer.

16. 14. The artificial turf fiber of claim 13, wherein the compatibilizer is any one of maleic acid grafted to polyethylene or polyamide; maleic anhydride grafted to a free radical initiated graft copolymer of polyethylene, SEBS, EVA, EPD, or polypropylene with an unsaturated acid or its anhydride, such as maleic acid, glycidyl methacrylate, ricinolol oxazoline maleinate; a graft copolymer of SEBS and glycidyl methacrylate; a graft copolymer of EVA with mercaptoacetic acid and maleic anhydride; a graft copolymer of EPDM and maleic anhydride; a graft copolymer of polypropylene and maleic anhydride; a polyolefin-graft-polyamide, polyethylene or polyamide; and a polyacrylic acid type compatibilizer.

17. An artificial turf fiber, The artificial turf fibre is an artificial turf fibre according to any one of claims 1 to 12, wherein the artificial turf fibre comprises 60 to 99% by weight of the artificial turf fibre of an LLDPE polymer and 1 to 15% by weight of the artificial turf fibre of an LDPE polymer, or 17. The artificial turf fiber of any one of claims 13 to 16, wherein the second polymer comprises 60 to 99% by weight of the second polymer of an LLDPE polymer and 1 to 15% by weight of the second polymer of an LDPE polymer.

18. 0.918 g / cm ３ ~0.920g / cm ３ the LLDPE polymer having a density in the range of 0.919 g / cm ３ ~0.921g / cm ３ and the LDPE polymer having a density in the range of

19. 17. Artificial turf fibres according to any one of the preceding claims, wherein the siloxanes grafted to the polymer each have a molecular weight of more than 3000 Daltons, in particular between 4000 and 6000 Daltons.

20. An artificial turf comprising the artificial turf fiber according to any one of claims 1 to 16.

21. 1. A method of producing an artificial turf fiber, the method comprising: Providing a base polymer; blending the base polymer with one or more siloxane-grafted polymers, wherein the one or more siloxane-grafted polymers are polyolefins or polyamides; extruding the mixture of the base polymer and the polymer grafted with one or more siloxanes into monofilaments to provide the artificial turf fiber, or extruding the mixture of the base polymer and the polymer grafted with one or more siloxanes into a film and cutting the film into slit film strands to provide the artificial turf fiber.

22. 22. The method of claim 21, wherein the base polymer is a mixture of two or more immiscible polymers, a first polymer forming beads surrounded by a second polymer, and the extrusion stretches the beads of the first polymer into thread-like regions comprised in the monofilament or film.

23. 22. The method of claim 21, wherein the base polymer is a mixture of two or more polymers that are coextruded.

24. 24. The method of any one of claims 21 to 23, wherein the mixture of the base polymer and the one or more siloxane-grafted polymers comprises the one or more siloxane-grafted polymers in an amount selected such that no more than 0.25% by weight of the artificial turf fibers consist of the one or more siloxane-grafted polymers.

25. 1. A method for producing artificial turf, comprising: Incorporating a plurality of artificial turf fibers according to any one of claims 1 to 16 into a liquid backing; allowing the liquid backing to solidify into a film, wherein the film surrounds and thereby mechanically secures at least a portion of the artificial turf fibers, with the solid film acting as an artificial turf backing.

26. 1. Use of one or more siloxane-grafted polymers as a processing aid to prevent clogging of an extrusion nozzle when a base polymer is extruded through a nozzle to form artificial turf fibers or to form a film that is cut into strands for use as artificial turf fibers, wherein the one or more siloxane-grafted polymers are polyolefins or polyamides, particularly when the base polymer is a blend of two or more immiscible polymers and / or the extrusion is a co-extrusion of two or more polymers through the same extrusion nozzle.

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