WRAPPING YARN FOR ARTIFICIAL TURF

Abstract

An artificial turf wrapping yarn made of polyethylene or polyethylene-polyamide polymer mixture with a compatibilizer. The wrapping yarn is adapted for wrapping around a plurality of turf fiber monofilaments to form a bundle of the turf fiber monofilaments and protect their integrity during securing the bundle of the turf fiber monofilaments to a carrier of the artificial turf.

Claims

1. An artificial turf wrapping yarn made of polyethylene or a polyethylene-polyamide polymer mixture with a compatibilizer.

2. The wrapping yarn of claim 1, wherein the wrapping yarn is adapted for wrapping a plurality of turf fiber monofilaments to form a bundle of the turf fiber monofilaments and protect their integrity during securing the bundle of the turf fiber monofilaments to a carrier of the artificial turf.

3. The wrapping yarn of claim 2, wherein the plurality of the turf fiber monofilaments are made of the same type of material like the wrapping yarn, in particular polyethylene, or a polyethylene-polyamide polymer mixture with a compatibilizer.

4. The wrapping yarn of claim 1, wherein the polyethylene in the polyethylene wrapping yarn comprises HDPE or HMPE or a combination thereof, wherein in particular the polyethylene-polyamide polymer mixture in the wrapping yarn or in the turf fiber monofilaments comprises 70% to 95%, or 80% to 90% PE by weight, 0.1% to 2% by weight of a compatibilizing agent, and the balance of the polymer mixture is polyamide.

5. The wrapping yarn of claim 1, wherein the wrapping yarn comprises a bundle of individual wrapping yarn monofilaments, preferably from about 20 to 50 individual wrapping yarn monofilaments, more preferably 30 to 40 individual wrapping yarn monofilaments.

6. The wrapping yarn of claim 5, wherein each of the individual wrapping yarn monofilaments has a cross section with a diameter of less than 50 micrometer, in particular 20 to 30 micrometers.

7. The wrapping yarn of claim 1, wherein the wrapping yarn is texturized, wherein in particular the wrapping yarn is texturized so that it shrinks upon being cut and temperature treatedstarting from a maximum expanded stateto less than 60% of its original length when wrapping the fiber bundle, in particular to less than 50% of its original length, for example to less than 30% or less than 20% of its original length.

8. The wrapping yarn of claim 1, wherein the wrapping yarn is a bundle of multiple wrapping yarn monofilaments, the said monofilaments being formed by extruding the individual wrapping yarn monofilaments from an extruder through a plurality of extrusion nozzle openings and bundling the extruded individual wrapping yarn monofilaments to form the wrapping yarn.

9. The wrapping yarn of claim 1, wherein the wrapping yarn has a weight of less than 50 g, preferably less than 40 g per 10.000 m of the wrapping yarn.

10. The wrapping yarn of claim 1, wherein the wrapping yarn is made of polyethylene which has an MFI (Melt flow index/melt flow rate) of at least 1.0 g/min, in particular from 1.0 g/min to 200 g/min, in particular from 3.0 g/min to 50 g/min, in particular from 5.0 g/min to 30 g/min, in particular from 15.0 g/min to 30 g/min measured according to the ISO standard 1133-1 at 190 C. and a weight of 2.16 kg, and/or has a density below 0.925 g/cm.sup.3.

11. The wrapping yarn of claim 1, wherein the wrapping yarn comprises a nucleating agent, in particular sorbic acid.

12. The wrapping yarn of claim 1, wherein the wrapping yarn comprises a radically crosslinked polyethylene.

13. An artificial turf fiber bundle, comprising: a plurality of turf fiber monofilaments, the plurality of artificial turf fiber preferably comprising at least 3, more preferably 5 to 10, and most preferably 6 to 8 turf fiber monofilaments, and the wrapping yarn of claim 1, wherein the wrapping yarn is wrapped around the plurality of the turf fiber monofilaments such that a bundle of artificial turf fiber is formed, wherein the turf fiber monofilaments comprise polyethylene or a polyethylene-polyamide mixture with a compatibilizer.

14. An artificial turf comprising: a plurality of artificial turf fibers which are integrated in bundles at puncture points in a carrier, and the wrapping yarn according to claim 1, wherein the wrapping yarn is integrated into the carrier at the puncture points.

15. The artificial turf of claim 14, wherein the length of the wrapping yarn between the puncture points and the ends of the wrapping yarn comprises a plurality of texturized wrapping yarn fibers, and/or wherein in particular the wrapping yarn fibers have a length of less than 60% of the length of the artificial turf fibers, in particular of 30% of the length of the artificial turf fibers, preferably to less than 20% of the length of the artificial turf fibers, and more preferably to less than 10% of the length of the artificial turf fibers.

16. A method for manufacturing a wrapping yarn for artificial turf, the method comprising: extruding polyethylene or a polyethylene-polyamide mixture with a compatibilizer, into a plurality of monofilaments; and bundling the plurality of monofilaments together to form the wrapping yarn.

17. The method of claim 16, wherein the extrusion of the wrapping yarn monofilaments is performed at a temperature of at least 190 C., in particular at least 230 C., in particular 240 C. to 260 C.

18. A method of manufacturing artificial turf by using the wrapping yarn of claim 1 or the artificial turf fiber bundle of claim 13, the method comprising: providing a plurality of turf fiber monofilaments; using the wrapping yarn to wrap around a plurality of turf fiber monofilaments to form a continuous turf fiber bundle of turf fiber monofilaments wrapped with the wrapping yarn; tufting the continuous turf fiber bundle through a carrier to form loops of the turf fiber bundle on a front side of the carrier; and cutting the loops to form a plurality of free end fibers per loop pointing out from the carrier to form a grass-like artificial turf surface, wherein in particular the wrapping yarn that is wrapped around each bundle upon being cut shrinks to less than 30% of its original length when wrapping the fiber bundle, preferably to less than 20% of its original length, and more preferably to less than 10% of its original length.

19. The method of claim 18, further comprising: after the tufting, applying a liquid backing onto a lower side of the carrier for fixing portions of the artificial turf fibers and portions of the wrapping yarn in the carrier, the lower side being the side opposed to the side to which the cut artificial turf fibers emerge; and applying heat for letting the applied liquid backing solidify.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0108] In the following, embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

[0109] FIG. 1A is a flowchart of a method of manufacturing a wrapping yarn;

[0110] FIG. 1B is a flowchart illustrating a method of manufacturing a wrapping yarn made from a PE/PA polymer;

[0111] FIG. 1C is a flowchart illustrating a method of manufacturing a PE/PA polymer mixture;

[0112] FIG. 1D is a simplified cross-sectional view of a PE/PA polymer mixture;

[0113] FIG. 1E illustrates the extrusion of the polymer mixture into a monofilament;

[0114] FIG. 1F shows a cross-section of a small segment of the monofilament;

[0115] FIG. 1G illustrates the effect of stretching the monofilament;

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

[0117] FIG. 3A is a simplified schematic illustration of an artificial turf with the artificial turf fiber loops and the polyethylene wrapping yarn in its extended form wrapped around the turf fiber bundle;

[0118] FIG. 3B is a simplified schematic illustration of the artificial turf of FIG. 3A after the loops are cut and the polyethylene wrapping yarn has shrunk;

[0119] FIG. 4 is an image of a wrapping yarn made of polyethylene;

[0120] FIG. 5 is an image of a wrapping yarn made of polyester;

[0121] FIGS. 6, and 7 are DSC analysis graphs of the polyethylene wrapping yarn of FIG. 4, and the polyester wrapping yarn of FIG. 5, respectively.

DETAILED DESCRIPTION

[0122] 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 their function is equivalent.

[0123] The present invention provides a polyethylene wrapping yarn for an artificial turf for wrapping around a plurality of polyethylene turf fiber monofilaments to form a turf fiber that is a bundle of the polyethylene turf fiber monofilaments and protect the integrity of the turf fiber bundle during the tufting process of stitching the turf fiber bundle through a carrier of the artificial turf.

[0124] The polyethylene wrapping yarn comprises a bundle of individual polyethylene yarn monofilaments, preferably from about 20 to 50 individual polyethylene yarn monofilaments, more preferably 30 to 40 individual polyethylene yarn monofilaments.

[0125] Each of the individual polyethylene yarn monofilaments may have a very thin cross-section, for example, a circular cross section with a diameter of 20 to 30 micrometers. The polyethylene wrapping yarn is heavily texturized so that it shrinks upon being cut to less than 30% of its original length when it is extended and wrapping the turf fiber bundle, preferably to less than 20% of its original length, and more preferably to less than 10% of its original length. It has been found that compared to existing wrapping yarn made from polyester, the polyethylene wrapping yarn according to the present invention can be readily texturized to a greater degree than the polyester wrapping yarn. This is advantageous because it reduces the footprint of the polyethylene wrapping yarn that remains in the final artificial turf structure and makes it less visible to the user of the artificial turf. This is particularly useful for artificial turf structures that do not use infill material.

[0126] In addition, the higher shrinkage may allow wider opening of the turf fiber monofilaments that make up each turf fiber bundle once the turf fiber loops are cut which results in a more homogeneous and more dense turf fiber surface for the artificial turf.

Making the Polyethylene Wrapping Yarn

[0127] Referring to FIG. 1A, a method of making the polyethylene wrapping yarn includes forming polyethylene, preferably high density polyethylene HDPE, into a plurality of wrapping yarn monofilaments according to step 102. For example, forming the plurality of the turf fiber monofilaments may include extruding the individual wrapping yarn monofilaments from an extruder through a plurality of nozzle openings of an extrusion apparatus. An example of extruding a monofilament from a polymer mixture is shown in FIG. 1E for a PE/PA polymer mixture, however, the same extrusion apparatus may also be used for extruding a polyethylene monofilament.

[0128] Alternatively, the turf fiber monofilaments may be formed by first forming a film shape filament, e.g., also by extrusion but using a different nozzle opening, and then splitting the film into a plurality of polyethylene wrapping yarn monofilaments.

[0129] The method for making the polyethylene wrapping yarn may further include bundling the plurality of the polyethylene wrapping yarn monofilaments together to form the polyethylene wrapping yarn according to step 104.

[0130] The extrusion nozzle or plate of the extrusion apparatus may preferably have from 20 to 50 openings (or holes), preferably from 30 to 40 openings. In FIG. 1E a one hole plate is shown as an example. In a more specific example, the plate of the extrusion nozzle may have 36 openings allowing extruding 36 monofilaments at the same time. Hence, during the extrusion, melted polyethylene exits in the form of a plurality of wrapping yarn monofilaments, each monofilament having a cross-sectional diameter of preferably from 20 to 30 micrometers. The extrusion apparatus used for the making of the very thin monofilaments that form the polyethylene wrapping yarn by bundling them together needs to be fitted with an outlet plate having a plurality of very small openings, i.e., preferably 20 to 50 openings, or more preferably 30 to 40 openings. In a specific embodiment the plate may have 36 openings.

[0131] FIG. 18 is a flowchart illustrating a method of manufacturing wrapping yarn monofilaments from a PE/PA polymer mixture. Adding PA in the PE polymer mixture increases the rigidity and tensile strength of the produced wrapping yarn monofilaments which forms after the bundling of the monofilaments a more rigid, higher tensile wrapping yarn.

[0132] The method comprises forming a polymer mixture comprising a three-phase system of PA, PE and a compatibilizer (also referred to as a compatibilizing agent) according to step 105. The PA and PE polymers are immiscible and the PA forms polymer beads surrounded by the compatibilizer within the second polymer. In the next step 106, the PE/PA polymer mixture is extruded into a monofilament. Next in step 107 the monofilament is quenched or rapidly cooled down. Next in step 108 the monofilament is reheated and, according to step 109 the reheated monofilament is stretched to deform the PA polymer beads into thread-like regions and to form the monofilament into a wrapping yarn monofilament with a desired diameter, crystallinity, and tensile strength.

[0133] According to step 110 a plurality of wrapping yarn monofilaments are bundled together and texturized to form the polyethylene wrapping yarn.

[0134] FIG. 1C is a flowchart illustrating a method of creating the PE/PA polymer mixture. The PE/PA polymer mixture is a three-phase system comprising PA polymer, PE polymer and the compatibilizer. The PE/PA polymer mixture may also comprise other additives such as color or flow agents for improving the flowing properties of the polymer mixture during extrusion.

[0135] Accordingly, a method for forming the PE/PA polymer mixture may comprise first, in step 120 forming a PA polymer mixture by mixing the PA polymer with the compatibilizer. Additional additives may also be added during this step. Next in step 121 the first mixture is heated. Next in step 122 the PA mixture is extruded. Then in step 123 the extruded PA mixture is granulated or chopped into small pieces. Next in step 124 the granulated PA mixture is mixed with the PE polymer. Additional additives may also be added to the polymer mixture at this time. Finally in step 125 the granulated PA mixture is heated with the PE polymer to form the PE/PA polymer mixture. The heating and mixing may occur at the same time.

[0136] FIG. 1D shows a diagram which illustrates a cross-section of a PE/PA polymer mixture 400. The PA/PE polymer mixture 400 comprises a PA polymer 402, a PE polymer 404, and a compatibilizer 406. The PA polymer 402 and the PE polymer 404 are immiscible. The PA polymer 402 is less abundant than the PE polymer 404. The PA polymer 402 is shown surrounded by the compatibilizer 406 and dispersed within the PE polymer 404. The PA polymer 402 surrounded by the compatibilizer 406 forms several polymer beads 408. The polymer beads 408 may be spherical or oval in shape or they may also be irregularly-shaped depending up on how well the polymer mixture is mixed and the extrusion conditions such as the temperature of the heated polymer mixture. The PE/PA polymer mixture 400 is a three-phase system. The first phase is made of the regions of the PA polymer 402, the second phase is the compatibilizer 406 and the third phase region is the PE polymer 404. The compatibilizer 406 separates the PA polymer 402 from the PE polymer 406.

[0137] FIG. 1D illustrates the extrusion of the PE/PA polymer mixture into a monofilament, Shown is an amount of a PE/PA polymer mixture 600. Within the PE/PA polymer mixture 600 there are many PA polymer beads 408 separated from the PE polymer 404 by the compatibilizer. A screw, piston or other device is used to force the polymer mixture 600 through a hole 604 in a plate 602. This causes the PE/PA polymer mixture 600 to be extruded into a monofilament 606. The monofilament 606 is shown as containing the PA polymer beads 408. The PE polymer 404 and the PA polymer beads 408 are extruded together. In some examples the PE polymer 404 will be less viscous than the PA polymer beads 408 and the PA polymer beads 408 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 in the core region of the monofilament 606 endowing the monofilament with a softer outside surface and a more rigid core.

[0138] FIG. 1E shows a cross-section of a small segment of a wrapping yarn monofilament 606 comprising the PA polymer beads 408 mixed inside the PE polymer and separated from the second polymer 404 by the compatibilizer 406 (not shown). To form the threadlike structures a section of the monofilament 606 is heated and then stretched along the length of the monofilament 606. This is illustrated by the arrows 700 which show the direction of the stretching.

[0139] FIG. 1F illustrates the effect of stretching the monofilament 606. In FIG. 1F an example of a cross-section of a stretched monofilament 606 is shown. The PA beads 408 in FIG. 1G have been stretched into thread-like structures 800. The amount of deformation of the PA polymer beads 408 depends upon how much the monofilament 606 has been stretched.

Bundling of the Polyethylene Wrapping Yarn Monofilaments

[0140] Bundling the individual wrapping yarn monofilaments together to form the polyethylene wrapping yarn may be done using any suitable method. For example, bundling may be performed via twisting or via a jet-knot process.

[0141] The bundling of the individual wrapping yarn monofilaments together allows creating a polyethylene yarn filament that has adequate tensile strength to withstand the tufting process forces and protect the turf fiber bundle during tufting.

[0142] According some embodiment, a twisting method may be used for forming the bundle of the polyethylene wrapping yarn monofilaments. Accordingly, wrapping yarn monofilaments after being formed via the extrusion process (or via the film and splitting process) may be fed into a twisting machine that twists the monofilaments together to form the polyethylene wrapping yarn bundle. By selecting the size and number of the individual wrapping yarn monofilaments the twisting provides a bundle that has an adequate tensile strength.

[0143] Multiple wrapping yarn monofilaments may be fed in the twisting machine to create an adequately strong wrapping yarn bundle. In the twisting machine, the polyethylene wrapping yarn monofilaments are subjected to a twisting action which involves rotating the polyethylene wrapping yarn monofilaments in the opposite direction to their natural twist (known as S-twist or Z-twist) to create a balanced wrapping yarn. Tension is carefully controlled during the twisting process to ensure uniformity and prevent yarn breakage. Too much tension can weaken the yarn, while too little tension can result in uneven twisting. The direction of twist (S-twist or Z-twist) can vary. S-twist involves twisting to the left, while Z-twist involves twisting to the right. As the polyethylene wrapping yarn monofilaments are twisted together, the resulting twisted wrapping yarn is wound onto a bobbin or spool to form a yarn bundle.

[0144] According to some embodiments, a jet knot process (also known as air jet knotting or air knotting) may also be used for bunding the polyethylene wrapping yarn monofilaments to form a yarn bundle during the winding or stretching of the polyethylene wrapping yarn monofilaments following the extrusion of the polyethylene wrapping yarn monofilaments from the extrusion.

[0145] For example, the jet knot process may, for example, use compressed air to bundle the individual yarn monofilaments. As the yarn monofilaments exit the extrusion openings a high-pressure air nozzle is used to blow a jet of air onto the plurality of the yarn monofilaments causing them to come into contact temporarily. The yarn monofilaments are then twisted together, and the air jet helps to secure them in place temporarily. While the yarn monofilaments are twisted together, knots may be formed due to the twisting action at predetermined intervals. The number of knots may differ. In an embodiment a knot may be formed every some centimeters, for example every 2 to 3 centimeters. In an embodiment the knots may be formed temporarily and may be later undone during further processing.

Texturizing the Polyethylene Wrapping Yarn

[0146] Texturizing the polyethylene wrapping yarn may be performed using any suitable method. For example, the polyethylene wrapping yarn may first be heated to soften before introducing crimps, or waves in the yarn by passing the polyethylene wrapping yarn through a series of rollers, plates, or gears that introduce tension, twists, or random undulations into the polyethylene wrapping yarn.

[0147] In an embodiment, air jet texturing may be used. Accordingly, high-speed air jets may be used to create turbulence and cause the monofilaments to crimp or curl as they cool down.

[0148] Another method that may be used is twist texturing by twisting in one direction and then untwisting in the opposite direction. After texturing, the polyethylene wrapping yarn is rapidly cooled to set the new textured structure. This ensures that the polyethylene wrapping yarn maintains its desired shape and characteristics. The textured wrapping yarn is cut into a desired length and can be used for wrapping the polyethylene turf fiber bundles to protect the polyethylene turf fibers as they are tufted through the carrier of the artificial turf.

[0149] It has been found that the polyethylene wrapping yarn can be readily texturized at a greater degree than polyester wrapping yarn that is currently used for wrapping polyethylene turf fiber bundles.

[0150] Texturizing may be performed on the individual filaments before they are bundled or may be performed to the polyethylene wrapping yarn bundle. According to some embodiments, texturizing includes air texturizing. For example, the polyethylene wrapping yarn may pass through a texturizing jet of compressed air which disrupts the smooth surface of the polyethylene wrapping yarn and creates crimps, loops, or other desired textures. The air jet parameters such as air pressure, temperature, and nozzle design may be adjusted to achieve different textures and degree of texturization. The textured wrapping yarn may then be cooled to set the new texture in place, for example, by passing the polyethylene wrapping yarn through a cooling chamber or over cooling rollers. The final textured (or texturized) wrapping yarn is wound onto bobbins or spools before use.

Making the Artificial Turf

[0151] Referring now to FIG. 2, a method for making an artificial turf comprises providing a plurality of turf fiber monofilaments according to step 202, using a polyethylene wrapping yarn to form a turf fiber bundle by wrapping the polyethylene wrapping yarn around the plurality of the turf fiber monofilaments according to step 204, tufting the turf fiber bundle through a carrier to form loops on a front side of the carrier according to step 206, and cutting the loops to form free end fibers according to step 208. The cutting of the loops also cuts the polyethylene wrapping yarn which retracts and shrinks to its textured shape. The polyethylene wrapping yarn may shrink to less than 30%, preferably less than 20%, and more preferably less than 10% of its original length when it is wrapped around the turf fiber loop according to step 210. Once the loops are cut, each loop forms two sets of free end turf fiber bundles and the polyethylene wrapping yarn retracts in its shrank, textured state.

[0152] FIGS. 3A and 3B show how a bundle of a plurality of artificial turf fibers can be secured to a carrier 308, e.g., a textile plane, by means of tufting. Accordingly, the artificial turf fiber bundle 310 wrapped with the polyethylene wrapping yarn 507 can be pierced through the carrier 308 multiple times to form loops of the fiber on a front side of the carrier according to a tufting method. After the tufting is competed, as depicted in FIG. 3A, there is a plurality of short U-shaped loops of the fiber pointing outside of the carrier's surface. Then, one or more blades cut 502 through the loops. As a result of the cutting step, two artificial turf fiber bundles per loop are created with each turf fiber bundle having a plurality of free end fibers 501 pointing out from the carrier and a grass-like artificial turf surface is generated.

[0153] As a result of the cutting step, the polyethylene wrapping yarn 507 is also cut and shrinks in one or more wrapping yarn filaments in their textured shrank state 508. The tufting process forms, first parts 506 of the artificial turf fiber bundle exposed to a bottom side of the carrier 308, second parts 302 exposed to a top side of the carrier 308 and intermediate parts 504 being inside the carrier 308.

[0154] In an embodiment the tufting process may include loading the carrier material in a machine equipped with rows of needles or tufting heads. The turf fiber bundle wrapped with the polyethylene wrapping yarn is fed into the tufting machine and as the carrier material moves through the tufting machine, the needles push the turf fiber bundle through the carrier creating loops of the turf fiber bundle on the surface of the carrier. For example, the portions of the continuous turf fiber bundle that pierces through the carrier may include 180 stitches per meter of tuft row and form 52 tuft rows per meter. Each tuft bundle/stitch after loop cutting may correspond to 6 open fiber ends, resulting in 180526 open fiber ends per square meter. During this stitching process the wrapper yarn helps to keep the monofilaments making the turf fiber bundle together. See FIG. 3A. After the loops are cut the polyethylene wrapping yarn (which is highly texturized) shrinks to its textured state as it gets also cut when the loops are cut.

[0155] The shrinkage may be further increased by heating the artificial turf after loop cutting and, in some instances, after applying a backing on the back of the carrier. For example, some artificial turfs, following the tufting process, may have an artificial turf backing applied on the back side of the carrier 308 to cover the parts 506 of the turf fiber bundle. The backing may be, for example, a polyurethane backing and may be applied by adding a viscous polyurethane reaction mixture on the back side of the carrier 308 to cover the parts 506. The carrier may be a textile mesh or may comprise perforations that allow the fluid polyurethane mixture at the bottom side of the carrier to flow in the carrier and maybe even slightly above the front side of the carrier. Thus, the carrier and parts of the fibers inserted in the carrier may become embedded in the polyurethane backing.

[0156] For example, the polyurethane fluid mixture may be a mixture of polyols and polyisocyanates that solidifies into a polyurethane backing, however, any other type of backing may also be used. Also, the present invention is not limited to artificial turfs with a backing. Many artificial turf structures may not have a backing and may be securely placed on a flat substrate structure other than a backing.

EXAMPLES

[0157] In example 1, a polyethylene (PE) wrapping yarn comprising a bundle of 18 filaments (see FIG. 4) was formed and analyzed in comparison to comparative example 1, i.e., a wrapping yarn made from polyester (PES) comprising a bundle of 35 PES filaments (see FIG. 5). The PE wrapping yarn was made of 18 filaments and had a thickness of 12 dtex and a combined linear density of 214 dtex. (12 dtex, bobbin 214 dtex 18 filaments).

[0158] The PES wrapping yarn was made of 35 filaments had a thickness of 5 dtex and a combined linear density of 180 dtex (5 dtex, bobbin 180 dtex/35 Filaments).

[0159] Shrinkage and tensile strength analysis data for example 1 and comparative example 1 are presented in Table 1.

TABLE-US-00001 TABLE 1 EXAMPLE 1 (PE) C. EXAMPLE 1 (PES) Shrinkage 10% 5% Tensile strength 1.1 N/m.sup.2 3.4 N/m.sup.2

[0160] DSC analysis for the PE and PES wrapping yarns are shown in FIGS. 6 and 7 respectively.

[0161] Importantly, the wrapping yarn made of polyethylene of example 1 exhibits adequate tensile strength, and shrinkage and provides excellent protection of polyethylene turf fiber bundle (made of polyethylene, or a PE/PA mixture with compatibilizer) during tufting to a variety of carriers. The artificial turf backing may for instance be a textile or other flat structure which is able to have fibers tufted into it.

[0162] 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.

[0163] For example, although the description of the composition and formation of the polyethylene-polyamide mixture with the compatibilizer in reference to the figures refers primarily to the use of the polyethylene-polyamide mixture in making the wrapping yarn, it should be understood that the same apply equally to the formation of turf fiber monofilaments from a polyethylene-polyamide polymer mixture with a compatibilizer such as, for example, a maleic anhydride grafted on polyethylene or polyamide. Use of the polyethylene-polyamide in making artificial turf fiber monofilaments is described in WO2015/144223A1 to Sick et al. entitled artificial turf and production method and which is incorporated herein by reference.

LIST OF REFERENCE NUMERALS

[0164] 102 to 210 process steps [0165] 302 tuft fibers on top side of carrier [0166] 308 carrier [0167] 400 PE/PA polymer mixture [0168] 402 PA polymer [0169] 404 PE polymer [0170] 406 compatibilizer [0171] 408 PA polymer beads [0172] 501 free end turf fibers [0173] 502 blades [0174] 503 turf fiber bundle [0175] 504 turf fiber inside the carrier [0176] 506 turf fiber loops on lower side of carrier [0177] 507 wrapping yarn wrapped around turf fiber bundle [0178] 508 wrapping yarn in shrank state [0179] 600 PE/PA polymer mixture [0180] 602 extrusion plate [0181] 604 hole of extrusion plate [0182] 606 monofilament [0183] 700 direction of stretching