ARTIFICIAL TURF WITH TRACTION CONTROL AGENT FOR HOCKEY FIELDS

Abstract

An artificial turf fiber comprising a polymer material and a traction control agent disposed within the polymer, wherein the traction control agent (404) is a grafted polymer (404) comprising a slip agent (302) grafted on a backbone (304) of the grafted polymer (404).

Claims

1-16. (canceled)

17. An artificial turf fiber for a hockey artificial turf, the fiber comprising: a base polymer, and a traction control agent in the base polymer, wherein the traction control agent is a grafted polymer comprising a slip agent grafted on a backbone of the grafted polymer.

18. The artificial turf fiber of claim 17, wherein the traction control agent is incorporated in the base polymer in an amount effective to reduce the friction coefficient of the artificial turf fiber from 5% to 50% compared to the friction coefficient of the artificial turf fiber without the traction control agent.

19. The artificial turf fiber of claim 17, wherein the base polymer comprises polyolefin, polyester or a polyamide or a combination thereof, and wherein the backbone of the traction control agent is made of the same type polymer as a main part of the base polymer, wherein the main part of the base polymer is a polymer making up at least 50% by weight of the base polymer.

20. The artificial turf fiber of claim 17, wherein the backbone of the grafted polymer is selected from the group consisting of polyolefins, polyesters, and polyamides, and wherein the slip agent grafted on the backbone of the grafted polymer is one or more siloxanes.

21. The artificial turf fiber of claim 17, wherein the traction control agent stays dispersed homogeneously within the base polymer for at least one year, preferably for at least 2 years, more preferably for at least 5 years, and most preferably for at least 10 years.

22. The artificial turf fiber of claim 17, wherein the base polymer is selected from a group consisting of polyolefins, polyesters, and polyamides, wherein a main part of the base polymer of at least 50%, by weight of the base polymer consists of a polyolefin and wherein the backbone of the grafted polymer is made of the same polymer type as the main part of the base polymer.

23. The artificial turf fiber of claim 17, wherein the base polymer is ULDPE, LDPE, LLDPE, HDPE, or mixtures thereof.

24. The artificial turf of claim 17, wherein the base polymer is a mixture of LDPE and LLDPE.

25. The artificial turf fiber of claim 17, wherein 0.01% to 0.25% by weight of the artificial turf fiber, consists of the grafted polyolefin grafted with the one or more siloxanes.

26. The artificial turf fiber of claim 17, wherein the grafted polymer is polyolefin grafted with one or more siloxanes and wherein the molecular weight of the polyolefin grafted with the one or more siloxanes is at least 2,000 Dalton and less than 1,000,000 Dalton.

27. The artificial turf fiber of claim 17, wherein the base polymer comprises: LLDPE-C6: 80-84 wt %, with at least 85 wt % of the LLDPE-C6 being biobased, HDPE: 8.0-12.0 wt %, with at least 90 wt % of the HDPE being biobased, masterbatch 6-10 wt %, process aid 0.1-0.5 wt %, and the traction control agent is a siloxane grafted polyolefin present in an amount of from 0.01 wt % to 0.25 wt %, and wherein the masterbatch includes color pigments and a UV stabilizer.

28. The artificial turf fiber of claim 17, wherein the grafted polymer is a polyolefin grafted with one or more siloxanes, and the amount of the one or more siloxanes grafted on the polyolefin is chosen so that the one or more siloxanes are solid or have a wax-consistency at room temperature.

29. The artificial turf fiber of claim 17, 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 wherein the first polymer forms threadlike regions surrounded by the compatibilizer within the second polymer.

30. The artificial turf fiber of claim 17, further comprising reflective particles and or reflective pigments for preventing overheating of the fiber, and wherein the fiber is texturized with at least 30% of the part of the fiber length which extends above the infill material having at least one of curl, or wave shape for enhanced softness and coverage.

31. An artificial turf comprising a plurality of the artificial turf fibers according to claim 17 which are securely attached to a backing material forming closed loops extending above a top surface of the backing.

32. A hockey field playing surface comprising the artificial turf of 31.

33. The artificial turf fiber of claim 17, wherein the base polymer is a mixture of LLDPE and HDPE with the amount of LLDPE in the polymer mixture being greater than the amount of the LDPE or the amount of HDPE in the mixture.

34. The artificial turf fiber of claim 17, wherein the base polymer is a mixture of LDPE and LLDPE, the LLDPE is from 10 to 70 wt % of the base polymer.

35. The artificial turf of claim 17, wherein the base polymer is a mixture of HDPE and LLDPE, wherein the HDPE has a density of 0.952 to 0.957 g/cm.sup.3 and is in an amount of 5.0 to 18 wt % of the total amount of HDPE and LLDPE.

36. The artificial turf fiber of claim 30, wherein the first polymer is a polyamide, and the second polymer is polyethylene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0114] In the following, embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

[0115] FIG. 1 is a flowchart of a method of manufacturing an artificial turf;

[0116] FIG. 2 is a flowchart of a method of manufacturing an artificial turf fiber;

[0117] FIG. 3 is a simplified schematic illustration of a polyolefin grafted with siloxanes;

[0118] FIG. 4 is a simplified schematic illustration of a base polymer comprising polyolefin grafted with one or more siloxanes and other additives;

[0119] FIG. 5 is a simplified schematic illustration of a polymer mixture comprising two polymers, a compatibilizer and a polyolefin grafted with one or more siloxanes;

[0120] FIG. 6 is a simplified schematic illustration of the process of extruding a polymer monofilament through an extrusion nozzle;

[0121] FIGS. 7A and 7B are a simplified schematic illustration of an artificial turf and its manufacturing;

[0122] FIGS. 8A and 8B are a simplified schematic illustration of an artificial turf and its manufacturing;

[0123] FIG. 9 shows a cross-section of a granular polymer mixture 900 comprising LLDPE and HDPE according to one example implementation;

[0124] FIG. 10 is a simplified block diagram of a system for synthesizing a grafted polyolefin.

DETAILED DESCRIPTION

[0125] Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent.

[0126] The present invention provides an artificial turf fiber comprising a base or matrix polymer forming a base or continuous matrix and a traction control agent incorporated/contained in the polymer material in an amount adequate to reduce the coefficient of friction of the turf fiber and keep it within a desired range for optimum traction between the turf surface and the user's shoes. The traction control agent is a grafted polymer comprising a slip agent polymer, preferably a siloxane, that is grafted on a backbone of an additive polymer.

[0127] Additive polymer refers to the polymer that serves as the backbone on which the slip agent, e.g., the siloxane is grafted. The additive polymer and the base polymer may preferably be the same type or the same to allow for better more homogeneous mixing of the traction control agent within the base polymer and as a result within the fiber. The slip agent polymer is added in the fiber in an effective amount designed to provide an effective reduction of the friction coefficient. Also, because the slip agent polymer is grafted on the backbone of the additive polymer it can last reducing the friction coefficient of the fibers preferably for a period of at least 5 years, more preferably at least 10 years, and most preferably at least 15 years.

[0128] Although we do not wish to be bound by theory, key factors which are believed to prevent the diffusion of the traction control agent to the surface of the fiber and out of the fiber include the type of the additive polymer, the type of the base polymer, the molecular weights of the base polymer, the additive polymer and the slip agent polymer, the hydrophilicity of the slip agent. Through extensive research and consideration of the above factors, the base polymer material for the fiber, the traction control agent (e.g., the siloxane grafted polyethylene) agent polymer and the additive polymer were selected.

[0129] In some specific embodiments the slip agent polymer is a siloxane and is used in an amount of 0.5 wt %, 1.0 wt % and 1.5 wt % based on the total weight of the turf fiber wherein the base polymer that forms the matrix of the fiber and the additive polymer which forms the backbone on which the siloxane chains are grafted may each be a mixture of 10 wt % LDPE and 90 wt % LLDPE of the holistic polymer weight. In yet other embodiments the siloxane is used in an amount of 0.5 wt %, 1.0 wt %, and 1.5 wt % based on the total weight of the turf fiber wherein the base polymer that forms the matrix of the fiber and the additive polymer which forms the backbone on which the siloxane chains are grafted may each be a mixture of 15 wt % HDPE (density of 0.955 g/cm3) and 85 wt % LLDPE (density of 0.920 g/cm3).

[0130] In some preferred embodiments, the fiber may also include a reflective agent such as reflective particles, and/or reflective pigments for preventing overheating of the fiber.

[0131] An example of a method for manufacturing the artificial turf comprises incorporating the artificial turf fiber into a carrier, and adding a viscous thermoset resin reaction mixture onto a back side of the carrier to form a thermoset resin backing. Various additives may be added in the thermoset reaction mixture including, for example, a biocide agent having antimicrobial, antibacterial and antifungal properties. Once the thermoset resin reaction mixture is placed on the back side of the carrier, hardening of the thermoset reaction mixture is performed to form a solid thermoset resin backing with a portion of the turf fiber which protrudes out of the back side of the carrier being securely embedded inside the solid mass of the thermoset resin backing. The thermoset resin may be any suitable resin. Preferably, the thermoset resin may be a polyurethane resin. In an embodiment, the polyurethane is the reaction product of first and second polyols with an isocyanate, wherein the first polyol is polyether polyol and/or polyester polyol having at least two (2) hydroxyl groups per molecule, wherein the second polyol is polybutadiene diol, wherein the isocyanate comprises isocyanate monomers, isocyanate polymers or isocyanate prepolymers or a mixture thereof, and wherein the isocyanate monomers, the isocyanate polymers and the isocyanate prepolymers have two or more isocyanate groups per molecule. The polybutadiene diol may be used in an amount of 0.5-10% by weight of a combination of the first polyol and the isocyanate, and may have a number average molecular weight in the range of 500 to 6000 g/mol, more preferably in the range of 1.500 to 4.500 g/mol. The polyurethane reaction mixture may further comprise a surfactant and other additives and fillers. The hardening of the fluid polyurethane mass can be performed, for example, by heating the polyurethane reaction mixture on the back side of the carrier to a temperature of 70-140 C.

[0132] The making of the turf fiber includes forming a polymer material mixture inside a first container, preparing an additive mixture including the traction control agent (e.g., the siloxane grafted polyethylene), and preferably also the reflective agent and optionally various other additives for the fiber in a separate or a plurality of separate smaller containers, mixing the polymer material mixture with the additive mixture to form an extrusion feed mixture that is fed to an extruder to form a monofilament (in actuality, typically a plurality of monofilaments). The monofilament exiting from the extruder is quenched, for example, by passing it through a water bath, and upon exiting from the water bath the monofilament is reheated, for example, in an air oven. The reheated monofilament is oriented by stretching the reheated monofilament to form an oriented monofilament which is used as the artificial turf fiber either individually or after being combined with other monofilaments. For example, through a well-known process multiple monofilaments may be combined to form an artificial turf fiber which can be rolled into a yarn. The traction control agent (e.g., the siloxane grafted polyethylene) and preferably also the reflective agent may be added in the additive mixture inside the smaller container. However, this is just an example, and it should be understood that the traction control agent (e.g., the siloxane grafted polyethylene) agent can be added also in the larger container directly with the polymer material mixture or as a separate feed to the extruder feed. The polymer mixture may further comprise a nucleating agent for crystallizing the polymer within and at the surface of the monofilament anti UV agents, anti-flame agents and other optional additives. The artificial turf fiber is typically a bundle of at least 5 monofilaments.

[0133] The reflective agent (e.g., reflective particles and/or a reflective pigments) may be used for counteracting the overheating of the turf. These reflective particles and reflective pigment have the advantage of cooling the artificial turf field, thereby compensating the missing cooling effect of the water when water is absent. Also, applicant has found that the type and amount of the reflective agent may affect the effective rate of migration of the traction control agent (e.g., the siloxane grafted polyethylene) agent in the polymer material matrix of the fiber.

[0134] The polymer material mixture and the additive mixture including the traction control agent (e.g., the siloxane grafted polyethylene) agent, preferably also the reflective agent may be blended using a blender or mixing device prior to add them to the extruder.

[0135] The term tufting as used herein refers to a method of incorporating a fiber into an existing carrier. Short U-shaped loops of fibers are introduced through the carrier from one side so that their ends point outside of the carrier in the other direction. Usually, the tuft yarns form a regular array of dots on the other side. On the one side of the carrier where the U-shaped loops are located, the tuft fibers may be tied for security, although they need not be. The ends of the tuft yarns can then optionally be frayed or otherwise processed, so that they will subsequently create a dense layer of fibers protruding from the carrier.

[0136] The term weaving as used herein is a method of incorporating an artificial turf fiber (which can be a monofilament or a bundle of monofilaments) into an existing carrier, whereby the artificial turf fiber and the fiber(s) that built the carrier are interlaced. The interlaced fibers and the mesh form a fabric like or cloth like structure. When an artificial tuft fiber is incorporated by weaving, the fiber interlaces a series of mesh fibers at least three times. Thus, when a fiber is incorporated by weaving rather than tufting, a higher fraction of the artificial turf fiber is interlaced in the carrier material. This may increase the resistance to wear and tear of the artificial turf.

[0137] According to embodiments, incorporating the artificial turf fiber into the carrier comprises: tufting the artificial turf fiber into the carrier. According to alternative embodiments, incorporating the artificial turf fiber into the carrier comprises weaving the artificial turf fiber into the carrier.

[0138] Referring now to FIG. 1 a flowchart is provided which illustrates an example of a method of manufacturing artificial turf. First in step 102 a polymer mixture such as the mixture 400 depicted in FIG. 4 is created. The polymer mixture 400 comprises at least one base polymer 402 (also referred to as a matrix polymer), a traction control agent (e.g., the siloxane grafted polyethylene) 404, and preferably a reflective agent 406 (e.g., reflective particles or pigment 406).

[0139] The polymer mixture may be created by putting all of the components that make it up together at once. For instance, the at least one base polymer 402, the traction control agent (e.g., the siloxane grafted polyethylene) 404, the reflective agent 408, the optional reflective agent 406 and any other additives (not shown) could be all added together at the same time. The polymer mixture could be thoroughly mixed for instance by using a mixer device. The desired distribution of the components can be achieved by using the proper rate or amount of mixing. The generated mixture could be forwarded to a one-screw feed or a two-screw feed for the extrusion. Additional optional substances may be added.

[0140] In step 104, the polymer mixture is extruded into a monofilament 506 as illustrated in FIG. 6. Next in step 106 the monofilament is quenched or rapidly cooled down. In step 108 the monofilament is reheated and in step 110 the reheated monofilament is stretched to form a monofilament that can directly be used as an artificial turf fiber or that can be bundled with additional monofilaments into an artificial turf fiber. Additional steps may also be performed on the monofilament to form the artificial turf fiber. For instance, the monofilament may be spun or woven into a yarn with desired properties. Next in step 112 the artificial turf fiber is incorporated into an artificial turf backing. The incorporation comprises a step 114 of arranging a plurality of the artificial turf fibers on a carrier 704 (see FIGS. 7 and 8). The carrier may be a textile plane, for example. The artificial turf fibers are arranged such that first parts 706 of the monofilaments are exposed to a bottom side of the carrier 704 and second parts 702 of said monofilaments are exposed to a top side of the carrier 704. The arranging could be accomplished by tufting or weaving the artificial turf fiber into the carrier 704, but other methods of arranging the fibers within the carrier 704 are also possible.

[0141] Then, in step 116 a resin reaction fluid mixture is added on the bottom side of the carrier such that at least the first parts become embedded in the fluid. Finally, in step 118, the fluid mixture is caused to solidify into a film. The film surrounds and thereby mechanically fixes at least the first parts 706 (and optionally also some portions 804 of the second parts 702 as shown in FIG. 8B) of the monofilaments in the film. The film, i.e., the solidified fluid, constitutes the backing 802.

[0142] FIG. 2 shows a flowchart which illustrates an example of a method of manufacturing an artificial turf fiber. First in step 202 a base polymer is provided. For example, the base polymer can comprise or consist of a molten polymer or polymer mixture. The base polymer may comprise one or more additives such as flame retardants, pigments, UV stabilizers, nucleating agents, dulling agents, anti-oxidants, or fillers.

[0143] Next in step 204, the polyolefin grafted with one or more siloxanes is mixed with the base polymer. For example, the mixing step 202 may be performed in the extruder by homogeneously mixing the polyolefin grafted with one or more siloxanes with the molten base polymer. The mixing may be performed with one or more stirrers. In some implementation variants, it is also possible to add the polyolefin grafted with one or more siloxanes to the base polymer before the base polymer enters the extrusion machine, e.g., when the base polymer still is in solid form. For example, the base polymer may have the form of polymer granules of a single type of polymer or of two or more different types of polymers. Optionally, the base polymer may comprise a polymer granulate fraction referred to as master batch which comprises pigments and/or further additives.

[0144] In some implementation variants, the base polymer is a polymer mixture having two or more different phases. For example, the base polymer may be a polymer mixture as illustrated in FIG. 5.

[0145] In the next step 206 the base polymer is extruded into a monofilament.

[0146] According to a preferred embodiment, several post-processing steps are performed on the extruded monofilament. For example, the monofilament is quenched, i.e., rapidly cooled down, e.g., by immersing the monofilament in cool water. Then, the monofilament can be reheated and the reheated monofilament can be stretched to form the monofilament into the artificial turf fiber. In case the base polymer is a multi-phase polymer mixture wherein the first polymer forms beads within the second polymer, the stretching step deforms the polymer beads into thread-like regions which provides additional rigidity to the fibers.

[0147] Next in step 208, the extruded monofilament is used as an artificial turf fiber. For example, the monofilament or a bundle of multiple monofilaments can be incorporated into a carrier to form an artificial turf. Additional steps may also be performed on the monofilament to form the artificial turf fiber. For instance, the monofilament may be spun or woven into a yarn with desired properties and the yarn could be incorporated into the carrier instead of the monofilament. The incorporation can be performed, for example, by tufting or weaving the artificial turf fiber into the artificial turf backing. Then in a further, optional step the incorporated artificial turf fibers may be fixed at a desired position in the carrier by adding a secondary backing at least onto one side of the carrier. For example, the secondary backing can be polyurethane or latex. A comparatively low concentration of the polyolefin grafted with the one or more siloxanes may ensure that the surface roughness of the fibers is still high enough to allow the secondary backing to firmly fix the fibers while at the same time provide and effective reduction in the friction coefficient of the turf.

[0148] FIG. 3 is an illustration of a polyolefin grafted with one or more siloxanes 300. The grafting is a statistical process. Preferably, the polyolefin grafted with one or more siloxanes has multiple siloxanes 302 grafted to the polyolefin backbone 304.

[0149] FIG. 4 is an illustration of a polymer mixture 400 comprising a polyolefin grafted with one or more siloxanes 404 and optionally a reflective agent 406 and other additives which are dispersed in the base polymer 400. The polyolefin grafted with siloxanes 404 may have been distributed in and mixed with the base polymer by a stirrer or screw. The base polymer comprises at least one polymer 402 such as polyethylene. The other additives may comprise a nucleating agent such as phthalocyanine green, or phthalocyanine blue, and/or UV stabilizers.

[0150] FIG. 5 depicts a base polymer 500 which is a polymer mixture. The polymer mixture comprises 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 mixture may further comprise a compatibilizer 504. The first polymer and the second polymer are immiscible. In other examples there may be additional polymers such as a third, fourth, or even fifth polymer that are also immiscible with the second polymer. There also may be additional compatibilizers which are used either in combination with 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 also be formed by additional polymers (e.g., the third, fourth, . . . , etc., polymer) which are not miscible in the second polymer and may be surrounded by the compatibilizer 504 or a different compatibilizer.

[0151] The polymer beads are surrounded by the compatibilizer and are within the second polymer or mixed into the second polymer. The base polymer 500 may also comprise other things such as additives to color or provide flame or UV-resistance or improve the flowing properties of the polymer mixture. In particular, the base polymer 500 comprises polyolefin grafted with one or more siloxanes 508.

[0152] FIG. 6 is an illustration of the process of extruding a polymer mixture into a monofilament 606 which can be used as artificial turf fiber. Shown is an amount of a base polymer in the form of a polymer mixture 600. Within the polymer mixture 600 there is a large number of polymer beads 610. The polymer beads 610 may be made of one or more polymers that is not miscible with the second polymer 602 and is also 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 a hole 603 in a plate 604. This causes the polymer mixture 600 to be extruded into a monofilament 606 and the polymer beads 610 to be stretched into thread-like regions 106. The second polymer 602 and the polymer beads 610 are extruded together. In some examples the second polymer 602 will be less viscous than the polymer beads 610 and the polymer beads 610 will tend to concentrate in the center of the monofilament 606. This may lead to desirable properties for the final artificial turf fiber as this may lead to a concentration of the thread-like regions 106 in the core region of the monofilament 606.

[0153] The polyolefin grafted with one or more siloxanes 608 is homogeneously dispersed in the base polymer 600 and may decrease the viscosity and adhesiveness of the base polymer. In examples where the base polymer comprises multiple immiscible polymers, the polyolefin grafted with one or more siloxanes may predominantly or solely be comprised in the one of the polymer having the highest share of the base polymer, e.g., the second polymer 602 into which the other, immiscible polymers are embedded as polymer beads 610. This may ensure that the polymer beads 610 do not fuse and separate into a polymer compartment at the extrusion nozzle which clogs the nozzle or generates shear forces which would tear the monofilament 606 apart. These shear forces could result from adhesion of the first polymer to the metal walls of the opening 603 in the plate 406 during the extrusion.

[0154] It should be noted that FIG. 6 does not represent the sizes of the polymer beads 610 and the polyolefin grafted with one or more siloxanes 608 to scale. According to examples, the additive is dispersed in the base polymer in a much more fine-grained manner, e.g., on the level of individual molecules or molecular aggregates, while the polymer bead in some examples will typically have a size of approximately 0.1 to 3 micrometer, preferably 1 to 2 micrometer in diameter. In other examples the polymer beads will be larger. They may for instance have a size with a diameter of a maximum of 50 micrometer.

[0155] In some embodiment the polymer beads comprise crystalline portions and amorphous portions. The polymer mixture is heated during the extrusion process and portions of the first polymer and also the second polymer may have a more amorphous structure or a more crystalline structure in various regions. Stretching the polymer beads into the thread-like regions may cause an increase in the size of the crystalline portions relative to the amorphous portions in the first polymer. This may lead for instance to the first polymer to become more rigid than when it has an amorphous structure. This may lead to an artificial turf with more rigidity and ability to spring back when pressed down. The stretching of the monofilament may also cause in some cases the second polymer or other additional polymers also to have a larger portion of their structure become more crystalline.

[0156] In a specific example of this the first polymer could be polyamide and the second polymer could be polyethylene. Stretching the polyamide will cause an increase in the crystalline regions making the polyamide stiffer. This is also true for other plastic polymers.

[0157] In another embodiment the step of providing a base polymer 600 comprises the step of creating of a polymer mixture used as the base polymer. The creation of the polymer mixture comprises forming a first mixture by mixing the first polymer with the compatibilizer. The creation of the polymer mixture further comprises the step of heating the first mixture. Then, a granulate is created by extruding the first mixture into a granulate. The creation of the polymer mixture further comprises the steps of mixing the first mixture with the second polymer. The creation of the polymer mixture further comprises the step of heating the granulated first mixture with the second polymer to form the polymer mixture. Then, e.g., during or after the heating, the polyolefin grafted with one or more siloxanes is added to the polymer mixture and mixed with the polymer mixture. For example, the adding the polyolefin grafted with one or more siloxanes to the polymer mixture may be performed in the extruder. This particular method of creating the polymer mixture may be advantageous because it enables very precise control over how the first polymer and the compatibilizer are distributed within the second polymer and enables a homogeneous mixing of the polyolefin grafted with one or more siloxanes into the resulting polymer mixture before it is extruded. For instance, the size or shape of the extruded first mixture may determine the size of the polymer beads in the polymer mixture.

[0158] In the aforementioned method of creating the polymer mixture for instance a so called one-screw extrusion method may be used. As an alternative to this the polymer mixture may also be created by putting all of the components that make it up together at once without an intermediate extrusion step. For instance, the first polymer, the second polymer and the compatibilizer and optionally also the polyolefin grafted with one or more siloxanes could be all added together at the same time, or subsequently, while the mixture is continuously agitated. Other ingredients such as additional polymers or other additives could also be put together at the same time and/or successively during constant agitation. However, it is also possible to add the polyolefin grafted with one or more siloxanes later, e.g., after having transferred the polymer mixture into the extruder. The amount of mixing of the polymer mixture could then be increased for instance by using a two-screw feed for the extrusion. In this case the desired distribution of the polymer beads can be achieved by using the proper rate or amount of mixing.

[0159] In some example implementations, the polymer mixture is at least a four-phase system. The polymer mixture comprises at least a third polymer. The third polymer is immiscible with the second polymer. The third polymer further forms the polymer beads surrounded by the compatibilizer within the second polymer. In some examples, the creating of the polymer mixture comprises the step of forming a first mixture by mixing the first polymer and the third polymer with the compatibilizer. The creating of the polymer mixture further comprises the step of heating the first mixture. The creating of the polymer mixture first comprises the step of extruding the first mixture. The creating of the polymer mixture further comprises the step of granulating the extruded first mixture. The creating of the polymer mixture further comprises mixing the first mixture with the second polymer. The creating of the polymer mixture further comprises the step of heating the first mixture with the second polymer to form the polymer mixture, and homogeneously mixing the polyolefin grafted with the siloxanes into the polymer mixture. This method may provide for a precise means of making the polymer mixture and controlling the size and distribution of the polymer beads using two different polymers. As an alternative the first polymer could be used to make a granulate with the compatibilizer separately from making the third polymer with the same or a different compatibilizer. The granulates could then be mixed with the second polymer to make the polymer mixture.

[0160] As an alternative to this, the polymer mixture could be made by adding the first polymer, a second polymer, the third polymer and the compatibilizer and optionally also the polyolefin grafted with the siloxanes all together at the same time and then mixing them more vigorously. For instance, a two-screw feed could be used for the extruder. According to some examples, the polyolefin grafted with the siloxanes are added later, e.g., are added to the polymer mixture having already been transferred into the extruder.

[0161] According to some examples, the third polymer is a polar polymer, e.g., polyamide. In some examples, the third polymer is polyethylene terephthalate, which is also commonly abbreviated as PET. In some examples, the third polymer is polybutylene terephthalate, which is also commonly abbreviated as PBT.

[0162] According to some examples, the polymer mixture comprises between 1% and 30% by weight the first polymer and the third polymer combined. In this example the balance of the weight may be made up by such components as the second polymer, the compatibilizer, and any other additional additives put into the polymer mixture. According to some examples, the thread-like regions have a diameter of less than 20 micrometer. According to some examples, the thread-like regions have a diameter of less than 10 micrometers. According to some examples the thread-like regions have a diameter of between 1 and 3 micrometers.

[0163] According to some examples the artificial turf fiber extends a predetermined length beyond the artificial turf backing. The thread-like regions have a length less than one half of the predetermined length. According to some examples the thread-like regions have a length of less than 2 mm.

[0164] According to some examples the polymer mixture comprises between 1 and 20% by weight of the first polymer and the third polymer combined. Again, in this example the balance of the weight of the polymer mixture may be made up by the second polymer, the compatibilizer, and any other additional additives.

[0165] According to some examples the polymer mixture comprises between 5% and 10% by weight of the first polymer and the third polymer combined. Again, in this example the balance of the weight of the polymer mixture may be made up by the second polymer, the compatibilizer, and any other additional additives.

[0166] According to some examples the polymer mixture comprises between 1% and 30% by weight the first polymer. In this example the balance of the weight may be made up for example by the second polymer, the compatibilizer, and any other additional additives.

[0167] According to some examples the polymer mixture comprises between 1% and 20% by weight of the first polymer. In this example the balance of the weight may be made up by the second polymer, the compatibilizer, and any other additional additives mixed into the polymer mixture.

[0168] According to some examples the polymer mixture comprises between 5% and 10% by weight of the first polymer. This example may have the balance of the weight made up by the second polymer, the compatibilizer, and any other additional additives mixed into the polymer mixture.

[0169] According to some examples the first polymer is polyamide or polyethylene terephthalate (PET) or polybutylene terephthalate (PBT).

[0170] According to some examples the second polymer is a non-polar polymer, e.g., polyethylene or polypropylene or a mixture of the aforementioned polymers. According to some examples the polymer mixture comprises between 80-90% by weight of the second polymer. In this example the balance of the weight may be made up by the first polymer, possibly the second polymer if it is present in the polymer mixture, the compatibilizer, and any other chemicals or additives added to the polymer mixture.

[0171] According to some examples the polymer mixture further comprises any one of the following: a wax, a dulling agent, an ultraviolet stabilizer, a flame retardant, an anti-oxidant, a pigment, and combinations thereof. These listed additional components may be added to the polymer mixture to give the artificial turf fibers other desired properties such as being flame retardant, having a green color so that the artificial turf more closely resembles grass and greater stability in sunlight.

[0172] Artificial turf comprising fibers made of one or more monofilaments comprising the above-mentioned thread-like regions may have the advantage of being extremely durable because the thread-like regions are embedded within the second polymer via a compatibilizer. They therefore do not have the ability to delaminate. Having the second polymer surrounding the first polymer may provide for a stiff artificial turf that is soft and feels similar to real turf. The artificial turf comprising these thread-like regions is distinct from artificial turf which is coextruded. In coextrusion a core of typically 50 to 60 micrometers may be surrounded by an outer cover or sheathing material which has a diameter of approximately 200 to 300 micrometers in diameter. In this artificial turf there is a large number of thread-like regions of the first polymer. The thread-like regions may not continue along the entire length of the monofilament. The artificial turf may also have properties or features which are provided for by any of the aforementioned method steps. Nevertheless, a combination of coextrusion and thread-like regions is possible, as is depicted in FIG. 1B.

[0173] FIGS. 7A and 7B show how a plurality of artificial turf fibers can be arranged in a carrier 704, e.g., a textile plane, by means of tufting. Tufting is a type of textile weaving in which an artificial turf fiber 701 (that may be a monofilament 506 or a bundle of multiple monofilaments) is inserted on a carrier 704. After the inserting is done, as depicted in FIG. 7A, short U-shaped loops of the fiber point outside of the carrier's surface. Then, one or more blades cut 602 through the loops. As a result of the cutting step, two artificial turf fiber ends per loop and monofilament point out from the carrier and a grass-like artificial turf surface is generated. Thereby, first parts 706 of the monofilaments of the artificial turf fibers having been inserted in the carrier 704 are exposed to a bottom side of the carrier and second parts 702 of said monofilaments are exposed to a top side of the carrier.

[0174] In a preferred embodiment for artificial turf for hockey fields the cutting step 602 is omitted and the artificial turf is made with the U-shaped loops forming the top surface of the turf.

[0175] FIG. 8 depicts the carrier 704 with the inserted filaments having been embedded within (FIG. 8A) or next to a surface of (FIG. 8B) an artificial turf backing 802. This is performed by adding a fluid in step 116 (see FIG. 1) on the carrier 704 such that the first parts 706 of the monofilaments become embedded in the fluid (FIG. 8A) or the first parts and some portions 804 of the second parts 702 of the monofilaments (FIG. 8B) become embedded in the fluid. The carrier may be a textile mesh or may comprise perforations that allow the fluid 802.2 at the bottom side of the carrier to flow to the upper side of the carrier and vice versa, thereby creating a portion 802.1 of the backing on top of the carrier. Thus, the carrier and parts of the fibers inserted in the carrier may become embedded in the backing 802. The artificial turf fibers 701 are shown as extending a distance 806 above the carrier 704. The distance 806 is essentially the height of the pile of the artificial turf fibers 701.

[0176] For example, the fluid may be a styrene-butadiene suspension that solidifies into a latex backing or, preferably, may be a mixture of polyols and polyisocyanates that solidifies into a polyurethane backing or any other kind of fluid that is capable of solidifying after a defined time period into a solid film. The fluid solidifies into a film 802, e.g., by a drying process or by a chemical reaction resulting in a solidification of the fluid. Such a chemical reaction can be, for example, a polymerization. The film surrounds and thereby mechanically fixes at least the first parts of the monofilaments of the arranged artificial turf fibers. The solid film acts as the artificial turf backing. In some examples, additional coating layers may be added on the bottom of the artificial turf backing.

[0177] According to some examples the integration of the artificial turf fibers in the carrier comprises weaving, bundling, or spinning multiple monofilaments together to create the artificial turf fiber. The incorporation of the artificial turf fiber into the artificial turf backing could for example be performed alternatively by weaving the artificial turf fiber into artificial turf backing (or fiber mat) during manufacture of the artificial turf carpet. This technique of manufacturing artificial turf is known from United States patent application US20120125474 A1.

[0178] According to some examples the artificial turf fiber is not a single monofilament but a combination of a number of fibers. According to some examples the artificial turf fiber is a yarn formed by spinning or twisting together individual strands of fiber. According to some examples multiple stretched monofilaments are bundled together to create the artificial turf fiber. Multiple, for example 4 to 8 monofilaments, could be formed or finished into a yarn.

[0179] FIG. 9 shows a cross-section of a granular polymer mixture 900 comprising LLDPE and HDPE according to one example implementation. The polymer mixture comprises the following components e.g., in the form of polymer granules that are molten later: [0180] a pure first LLDPE polymer 908 of a density of 0.919 g/cm3 and at an amount of 73% by weight of the polymer mixture. The first LLDPE polymer preferentially does not have any additives; [0181] a master batch 902 comprising the first LLDPE polymer having a density of 0.919 g/cm3 and at an amount of 10% by weight of the polymer mixture. The master batch may include additives; [0182] an LDPE polymer 904 of a density of 0.920 g/cm.sup.3 and at an amount of 7% by weight of the polymer mixture; and [0183] a second, low density LLDPE polymer 906 of a density of 0.916 g/cm.sup.3 and at an amount of 10% by weight of the polymer mixture.

[0184] Depending on the embodiments, the amount of the filler material, the master batch, the LDPE and the first and second LLDPE polymer may vary. Preferentially, the amount of the first LLDPE polymer 902 lacking the additives is in this case adapted such that all components of the polymer mixture add up to 100%. In the depicted example, the LLDPE polymer in fraction 908 and in the master batch 902 and the additives contained in the master mix may constitute 83% by weight of the polymer mixture 900. In other embodiments (not shown), the polymer mixture 900 may comprise up to 39% filler material. In case the polymer mixture comprises 1% LDPE polymer and 99% LLDPE polymer (no filler or additives), an LDPE/LLDPE weight ratio of 1:99 is used. In case the polymer mixture comprises 15% LDPE polymer and 60% LLDPE polymer (a large amount of filler and additives may be used), an LDPE/LLDPE weight ratio of 15:60 is used. Preferentially, the LDPE/LLDPE weight ratio is between 5:95 and 8:60, i.e., between 5.3% and 13.3%.

[0185] In the depicted example of FIG. 9, 0.05% by weight of the polymer mixture consists of the polyolefin grafted with the one or more siloxanes, preferably polyethylene grafted with the one or more siloxanes. The polyolefin grafted with the one or more siloxanes may for example be added in the master batch 902, but the present invention may not be limited in this way.

[0186] In some examples, the polymer components 902, 904, 906, 908 together form a first liquid phase (corresponding to the second polymer) that may in addition comprise an additional polymer, also referred to as 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 may be reduced in accordance with the amount of the additional polymer.

[0187] FIG. 10 shows a block diagram of a system for synthesizing maleic acid-grafted polyolefins (PO-g-MA). The PO-g-MA can then be used in further processing steps for synthesizing polyolefins grafted with one or more siloxanes (PO-g-Si). Shown is a twin screw extruder 956 comprising a die head 960. The extruder comprises a first opening 950 where a polyolefin (e.g., PP, PE, EVA (Ethylene-Vinylacetate-Copolymer), LLDPE, HDPE, LDPE etc.), a reactive monomer such as maleic acid anhydride (MA) having the chemical formula C.sub.4H.sub.2O.sub.3, and an initiator are fed into the extruder. The initiator may be, for example, a peroxide. In some embodiments, the extruder may comprise one or more separate openings 952 for adding the MA and the initiator separate from the polymer. The polyolefin is typically provided in the form of granulate or pellets. The reactive monomer may be provided e.g., as vinylic monomers such as maleic acid anhydride (MA). As an alternative to MA, glycidyl methacrylate (GMA) may also be used. A vacuum pump 958 is configured to transport the mixture of polymer, the reactive monomer and peroxide to the die head 960. The mixture of the polyolefin, the initiator and the reactive monomer are melt-extruded in order to generate a polyolefin grafted with MA (PO-g-MA). According to some examples, as a result of this synthesis step, 0.1% to 0.5% of the monomers of the polyolefin (e.g., ethylene monomers in case of a polyethylene) are functionalized with MA, thereby providing functionalized groups which allow to covalently link the siloxanes to the polyolefin backbone in a subsequent synthesis step. This process is also referred to as reactive extrusion, as a free-radical initiator attaches functional groups to a polyolefin chain by attaching the reactive monomers to the polyolefin chain. For example, the PO-g-MA can be maleic anhydride-grafted polyolefins with weight fractions of acid anhydride based on the total molecule in the range of 0.01-10 wt %, in particular 0.15-10 wt %.

[0188] The PO backbone may be any of the described PO homopolymers, or copolymers described in this application. According to some examples, the PO in the PO-g-MA is HDPE, or LLDPE. In some examples, instead of PO the backbone may be PA, or mixtures of PO and PA.

[0189] In some embodiments, the PO in the PO-g-MA may be any of ULDPE, LDPE, LLDPE, HDPE, or mixtures thereof. In some embodiments, the PO In some embodiments, the PO is a mixture of LDPE and LLDPE, or a mixture of LLDPE and HDPE, wherein the amount of the LLDPE in the polymer mixture is greater than the amount of the LDPE or the amount of HDPE in the mixture. In some embodiments, the PO is a mixture of LDPE and LLDPE, wherein the LLDPE is preferably from 10 to 70 wt % of the polymer material, more preferably from 15 to 50 wt %, and even more preferably from 25 to 45% of the total amount of LDPE and LLDPE. In some embodiments, the PO is a mixture of HDPE and LLDPE, wherein the HDPE has a density of 0.952 to 0.957 g/cm.sup.3 and is in an amount of 5.0 to 18 wt %, preferably 12 to 17 wt % of the total amount of HDPE and LLDPE.

[0190] In some embodiments the PO-g-MA may be PP-g-MA, or PP/PE-g-MA, wherein PP/PE refers to copolymers of polypropylene and polyethylene.

[0191] It is further noted that instead of a polyolefin (PO), another polymer material as any of the polymer materials described here may be added in the first opening 950, including for example, polyamides, polyesters, or mixtures thereof or any mixtures of polyamides, polyesters, and polyolefins. Preferably, a main part of the base polymer of these mixtures may be a polyolefin, and in particular, PP and/or PE, more in particular PE, and even more in particular ULDPE, LDPE, LLDPE, HDPE and mixtures thereof.

[0192] The MA content may be in the range of 0.5% to 2%, in particular about 1.0% by weight of the of the PO-g-MA molecule.

[0193] In a second synthesis step (not shown), the PO-g-MA is stirred in a batch reactor at 180 C. with hydroxy-functionalized siloxane to generate the polyolefins (PO) grafted with one or more siloxanes (PO-g-Si). For example, a PO-g-Si may be synthesized by reacting an anhydride group-containing polyolefin in a solvent with a hydroxy-functional, linear, organically modified siloxane. For example, the siloxanes can be polyester-modified siloxanes, for example ,-dihydroxypolyestersiloxanes. The reaction is commenced under vigorous stirring and elevated temperatures of 165-195 C. One or more organo-polysiloxanes can thereby be attached to a polyolefin backbone via ester linkages. Condensation between hydroxyl and anhydride groups results in a permanent chemical bond of the siloxane chains to the polymer matrix. As an alternative to the solvent-based approach, PO-g-Si can also be prepared, for example, under the action of shear forces, for example during incorporation into the polymer on an extruder. Instead of a hydroxy-functionalized siloxane, other types of chemically equivalent siloxanes may be used, e.g., amino-functionalized siloxanes.

[0194] The polyamides grafted with siloxanes may be synthesized analogously using e.g., anhydride group-containing polyamines.

[0195] According to some implementation variants, the polyolefin grafted siloxanes are synthesized as specified in the European patent application EP1211277 B1 which is included herein by reference in its entirety.

[0196] According to some embodiments, the molecular weights specified herein can be determined e.g., by measuring the melt flow rate in accordance with standard ASTM D1238 or ISO 1133.

[0197] According to embodiments, the polymer in the polymer grafted with one or more siloxanes is a non-polar polyolefin such as polyethylene. This may be beneficial as this may cause the polymer grafted with the one or more siloxanes to be basically apolar (non-polar), which may ease the integration in a largely non-polar base polymer matrix of the fiber, e.g., PE-based fibers. Currently, there are siloxane graft polymers commercially available which have an A-B block format, whereby the A block is a silicone, e.g., PDMS, and the B block is either a polyamide or a polyacrylate. The A:B ratio of these siloxane block polymers may be 1:1, for example. Both B-block variants are polar blocks and yield polar polymers, because the dipole moments between C and N or O atoms in the polyamide or polyacrylate blocks are very large. The A block (e.g., PDMS) is also polar. Hence, these polar graft polymers are less suited for use in a non-polar fiber base polymer, as the polar and non-polar polymers may not be miscible and may yield artificial turf fibers having a tendency to delaminate.

[0198] In some embodiments, the one or more siloxanes may include a modified siloxane that contains amide based or acrylic-based hydrophobic groups. The aforementioned functional groups may introduce hydrophobicity to the one or more siloxanes. The modified siloxane may be prepared and then grafted on the backbone (e.g., the polyolefin backbone) as described above. Preparing the modified siloxane may be done by any suitable method. For example, an aminopropyl-terminated siloxane compound may be used to introduce amine groups into the one or more siloxanes followed by reaction with a carboxylic acid to form the amide groups.

[0199] Suitable examples of modified siloxanes with acrylic-based functional groups may include (meth)acrylic-modified siloxane compounds modified at one end or both ends thereof with at least one (meth)acrylic group.

Examples

[0200] In Example 1 an amount of 0.2 wt %, of a siloxane grafted polyethylene (SGPE or PE-g-Si) was added in a base polymer which was a mixture of 60 wt % LDPE and 40 wt % LLDPE. The LDPE had a density of 0.905 g/cm.sup.3. The LLDPE had a density of 0.918 g/cm.sup.3 and was a copolymer of polyethylene and butene. No reflective agent was added. The polyethylene backbone of the SGPE was made of the same type polymer as the base polymer and had a molecular weight of 2 k Dalton. The siloxane was polydimethylsiloxane (PDMS) and had molecular weight of 1000 Dalton.

[0201] Additives such as color pigments, flame retardants were also added and the mixture was extruded in a conventional extrusion equipment to form an artificial turf fiber which was then added in an artificial turf structure having a polyurethane backing as described above with reference to the figures.

[0202] In examples 2-5 the same process was repeated with the key parameters shown in Table 1. For each of the examples 2-5, the polymer backbone of the SGPE was the same type polymer as the base polymer. In examples, 4-5 the fiber was texturized to have a top at least about 30% of its length which extends above the backing and any infill material in the shape of a wave. Compared to example 1 which comprised straight fibers, the turf made with the texturized fibers of examples 2 and 5 showed significant improvement in overall smoothness and coverage. The same process was repeated in total 5 times with the key compounds added each time shown in the Table 1 below.

TABLE-US-00001 TABLE 1 Ex. 1 EX. 2 Ex. 3 Ex. 4 Ex. 5 Polymer 1 LDPE LLDPE HDPE LLDPE LLDPE Polymer 1 0.905 0.918 0.94 0.918 0.918 density Polymer 1 60 20 100 70 30 WT % Polymer 2 LLDPE LLDPE HDPE HDPE Polymer 2 0.920 0.920 0.94 0.94 density Polymer 2 40 80 30 70 Wt % traction control SGPE SGPE SGPE SGPE SGPE agent (TCA) TCA amount 0.2 0.01 0.1 0.15 0.25 wt % Siloxane type PDMS PDMS PDMS PDMS PDMS Siloxane MW 1000 1000 1000 1000 1000 (Dalton) Backbone 2000 5000 5000 10000 30000 polymer MW (Dalton) Reflective NO Titanium Titanium Mixed Mixed Agent dioxide dioxide metal metal oxide oxide Reflective 1.0 1.0 1.0 1.0 agent amount wt % Fiber NO NO NO Yes, type Yes, type texturization waves waves 30% 30%

[0203] The above formed fibers in examples 1-5 were tested and compared with comparative examples 6-10. In comparative examples 6-10 the same fiber compositions as in examples 1-5 were used respectively, except that no traction control agent was used in the polymer mixtures as shown in Table 2.

TABLE-US-00002 TABLE 2 C.E. 6 C.E. 7 C.E. 8 C.E. 9 C.E. 10 Polymer 1 LDPE LLDPE HDPE LLDPE LLDPE Polymer 1 0.905 0.918 0.94 0.918 0.918 density Polymer 1 60 20 100 70 30 WT % Polymer 2 LLDPE LLDPE HDPE HDPE Polymer 2 0.920 0.920 0.94 0.94 density Polymer 2 40 80 30 70 Wt % traction control NO NO NO NO NO agent (TCA) Reflective NO Titanium Titanium Mixed Mixed Agent dioxide dioxide metal metal oxide oxide Reflective 1.0 1.0 1.0 1.0 agent amount wt % Fiber NO NO NO Yes, type Yes, type texturization waves waves 30% 30%

[0204] Significant improvement in the overall smoothness and tribological characteristics was observed between the examples 1-5 and their corresponding comparative examples 6-10. A significant reduction in the friction coefficient was observed in the examples 1-5 compared to their corresponding comparative examples 6-10 of at least 10%. In addition, it has been found, rather unexpectedly, that the above formed fibers with the SGPE prevent excessive slippage in rain/wet conditions while providing a sufficiently smooth surface in dry/sunny conditions. Thus, not only the need for watering the artificial turf is eliminated but also excessive slippage is prevented even in rain/wet conditions. Surprisingly slippage is not or not substantially increased with respect to dry conditions when the artificial turf becomes wet such as due to rainy weather, possibly because the SGPE also acts as a water repellant.

[0205] In example 11, LLDPE and HDPE together with an effective amount of a SGPE were used according to the following composition:

Base Polymer:

[0206] LLDPE-C6: 81.75 wt %; [0207] HDPE: 10 wt %; [0208] masterbatch 8 wt %, [0209] calcium stearate as process aid 0.25 wt %, and [0210] SGPE in an amount of from 0.01 wt % to 0.25 wt %.

[0211] The LLDPE-C6 was 85 wt % biobased, and the HDPE was 90 wt % biobased. The LLDPE-C6 had a density of 0.925 g/cm.sup.3. The HDPE had a density of 0.97 g/10 min. The density was measured by ASTM D4883-18 standard test method for measuring the density of polyethylene using ultrasound.

[0212] The SGPE had a backbone polymer of the same type as the base polymer grafted with the same siloxane as the one used in example 1.

[0213] In examples 12-16, the same formulation as in example 11 was used except that the SGPE was varied using 0.30 wt % in example 12, 0.35 wt % in example 13, 0.40 wt % in example 14, 0.45 wt % in example 15, and 0.5 wt % in example 16. The amount of the masterbatch was respectively adjusted. The SGPE was mixed in the masterbatch and added in the polymer together as part of the masterbatch.

[0214] The bio-based polyethylene materials were made from ethylene derived from bioethanol based on sugar cane and are fully recyclable. The biobased materials had some impurities and calcium stearate which was added by the manufacturer of the material as a process aid. The biobased LLDPE and HDPE are therefore chemically different from petrol-based LLDPE and HDPE, respectively.

[0215] The master batch was 50% color pigments with a polyethylene based carrier and 50% UV stabilizer comprising 1, 6 Hexane-diamine, octadecyl-3-(3,5-di-tertbutyl-4-hydroxyphenyl)-propionate, and pentaerythritol tetrakis(3-(3,5-di-ter-butyl-4-hydroxyphenyl) propionate).

[0216] Comparative example 17 used same composition as for example 11 except that no SGPE was used. Significant improvement in the overall smoothness and tribological characteristics was observed between the examples 11-16 and comparative example 17. A significant reduction in the friction coefficient was observed in the examples 11-16 compared to the comparative example 10 of at least 10% for an extended period of time. In addition, the above formed fibers with the SGPE in the above amounts prevent excessive slippage in rain/wet conditions while providing a sufficiently smooth surface in dry/sunny conditions. Thus, not only the need for watering the artificial turf is eliminated but also excessive slippage is prevented even in rain/wet conditions. Surprisingly slippage is not or not substantially increased with respect to dry conditions when the artificial turf becomes wet such as due to rainy weather.

[0217] In comparative examples 18, 19, and 20 the same base polymer compositions were used as in examples 1, 2, and 3, but instead of SGPE, free siloxanes were used in the same amount. Unlike the grafted siloxane the free siloxanes may migrate to the surface of the fiber and out of the fiber in a period of few months.

[0218] Although the invention has been described in reference to specific embodiments, it should be understood that the invention is not limited to these examples only and that many variations of these embodiments may be readily envisioned by the skilled person after having read the present disclosure which do not fall outside the scope of the invention as defined by the claims.

LIST OF REFERENCE NUMERALS

[0219] 100 artificial turf fiber [0220] 102 circular or ellipsoid cross section fiber profile [0221] 103 core [0222] 104 protrusion [0223] 106 thread-like region [0224] 110 cladding [0225] 112 undulated side [0226] 114 core-cladding-contact surface [0227] 115 bulge [0228] 116 straight side [0229] 118 concave side [0230] 120 artificial turf fiber [0231] 130 artificial turf fiber, cross section [0232] 140 cross section of artificial turf fiber [0233] 202-208 steps [0234] 300 polyolefin grafted with siloxanes [0235] 302 siloxane [0236] 304 polyolefin backbone polymer [0237] 400 polymer mixture or base polymer [0238] 402 base polymer [0239] 404 polyolefin grafted with one or more siloxanes [0240] 406 further additives [0241] 408 polymer bead [0242] 500 polymer mixture, base polymer [0243] 502 first polymer [0244] 504 compatibilizer [0245] 506 second polymer or main part of the base polymer [0246] 508 polyolefin grafted with one or more siloxanes [0247] 600 polymer mixture or base polymer [0248] 602 second polymer or main part of the base polymer [0249] 603 hole [0250] 604 plate [0251] 606 monofilament [0252] 608 polyolefin grafted with one or more siloxanes [0253] 610 first polymer (beads) [0254] 700 artificial turf [0255] 702 fiber height [0256] 704 carrier [0257] 706 tuft loops on lower side of carrier [0258] 708 knife cutting fiber loops on upper side of carrier [0259] 802 area with predominantly amorphous state [0260] 804 area of increased shear forces in polymer mixture [0261] 806 area of high shear forces [0262] 808 crystalline portions [0263] 810 opening of the nozzle [0264] 900 polymer mixture [0265] 902 master batch LLDPE fraction [0266] 904 LDPE polymer fraction [0267] 906 second LLDPE polymer fraction [0268] 908 (first/main) LLDPE fraction [0269] 956 twin screw extruder [0270] 958 vacuum pump [0271] 960 die head