WO2023072876A1

WO2023072876A1 - Artificial grass fibre for artificial turf

Info

Publication number: WO2023072876A1
Application number: PCT/EP2022/079664
Authority: WO
Inventors: Fabien TAILLIEU; Cowdy SAMYN; Nuria Villena LERIN
Original assignee: Beaulieu International Group Nv
Priority date: 2021-10-25
Filing date: 2022-10-24
Publication date: 2023-05-04

Abstract

The present invention in general relates to artificial grass fibres for an artificial turf having an asymmetrical cross-sectional shape. The present invention also relates to an artificial turf comprising artificial grass fibres having an asymmetrical cross-sectional shape. The present invention also relates to methods for producing such artificial grass fibres and for producing such artificial turfs. The present invention also relates to a spinneret cavity having an asymmetrical cross-sectional shape, and to spinnerets comprising such spinneret cavities.

Description

ARTIFICIAL GRASS FIBRE FOR ARTIFICIAL TURF

TECHNICAL FIELD

The present invention in general relates to artificial grass fibres for artificial turf having a specific cross-sectional shape, and methods for producing such artificial grass fibres.

BACKGROUND

Artificial turf is a fabric of artificial (synthetic) fibres made to look like natural grass. It is often used as a sports field, a playground, a residential lawn, or for landscaping purposes. Artificial turf comes in various qualities, from low-end mats with limited quality to high-end mats with a more natural look or improved comfort and quality for sports. Artificial turfs such as artificial sports fields and artificial lawns are typically composed of artificial grass fibres tufted together. These individual fibres typically have a specific cross-sectional shape, and various shapes exist in the prior art. While each of these shapes may have their specific advantages, they still have several drawbacks

For example for sports, the mats are configured to provide sufficient comfort (shockabsorption), resiliency and elasticity (e.g., for good ball bouncing effect) and may comprise infills. Professional sports turf is moreover bound to specific requirements, set by sports federations such as FIFA. The dimensional stability of the artificial turf is important when installing the artificial turf and will improve longevity. Professional sport turfs often comprise infill material to improve the overall performance. One issue is outflow of infill by drainage of rainwater. Better retention of the infill particles, or the possibility to omit them is desired. For residential lawns and landscape, which typically do not comprise infill but thatch yarns, the requirements are somewhat different, with the biggest requirement that they look and feel like natural grass. Despite continual efforts to make artificial turf look more natural, there is still a need for further improvement.

Therefore, there is mainly a need for a more random orientation of the fibres, whereby filaments of the same bundle are oriented into different directions. There is also still a need for artificial grass fibres that have improved resilience. There is also still a need for artificial grass fibres that allow for more natural looking grass. There is also still a need for artificial grass fibres that show improved strength. There is also still a need for artificial grass fibres that allow for less injuries, such as skin burns. There is also still a need for artificial grass fibres that are more shock absorbing. There is also still a need for artificial grass fibres that feel softer to the touch. There is also still a need for artificial grass fibres that show improved water retention since this helps to keep the artificial turf cool and prevents electrostatic charging of the turf. Specifically in sports turf, there is also still a need for artificial grass fibres that properly contain and hold any granular infill that may be added (e.g., rubber particles or sand), or even renders

RECTIFIED SHEET (RULE 91) ISA/EP the infill no longer necessary. There is also still a need for artificial grass fibres that are less susceptible to wear and tear, particularly after intensive use, for example as a sports field. There is also still a need for artificial grass fibres that can withstand heavy objects for an extended time, for example as an artificial lawn. There is also still a need for artificial grass fibres that are less susceptible to adverse and/or variable weather conditions. There is also still a need for artificial grass fibres that do not lie flat down together and form bare patches. There is also still a need for artificial grass fibres that obtain desired properties with less use of material. There is also still a need for an artificial turf that is more environmentally friendly. There is also a need for methods to produce artificial grass fibres with the desired properties, that are efficient and easy to implement.

It is also an objective of the present invention to combine the above objectives by providing natural-looking grass with improved mechanical properties. Preferably, such an artificial turf can also be made in an economical way.

SUMMARY OF THE INVENTION

The present invention, and embodiments thereof, provides a solution to one or more of these needs. (Preferred) embodiments of one aspect of the invention are also (preferred) embodiments of the other aspects of the invention.

In a first aspect, the present invention provides an artificial grass fibre for artificial turf, characterized in that the cross-sectional shape of the artificial grass fibre is asymmetrical with regards to reflection symmetry and is asymmetrical with regards to rotational symmetry.

In some preferred embodiments, the artificial grass fibre is a monofilament.

In some preferred embodiments, the artificial grass fibre has a helical shape. Preferably the helical shape has an average distance between each 180° rotation of at least 0.4 cm and at most 10.0 cm.

In some preferred embodiments, the fibre consists of two lengthwise sections, wherein one lengthwise section of the artificial grass fibre comprises a different shape and/or dimensions compared to the other lengthwise section of the artificial grass fibre.

In some preferred embodiments, the fibre comprises two lengthwise sections with essentially the same geometric shape, but wherein each lengthwise section has one or more different parameters for said same geometric shape.

In some preferred embodiments, at least one parameter differs in at least 10% between each lengthwise section.

In some preferred embodiments, one lengthwise section of the artificial grass fibre comprises one or more grooves and/or ribs, while the other lengthwise section comprises no grooves nor ribs. In some preferred embodiments, the artificial grass fibre has an asymmetrical double V shape, wherein one V differs from the other V in at least one, preferably two, more preferably all three aspects below: the inner angle between the legs for each of the V’s is different; the length of the legs for each of the V’s is different; and, one V is ribbed, while the other is not.

In some preferred embodiments, the artificial grass fibre has an asymmetrical double C shape, wherein one C differs from the other C in at least one, preferably two, more preferably all three aspects below: the inner radius of each of the C’s is different; the arc length of each of the C’s is different; and, one C is ribbed, while the other is not.

In a second aspect, the present invention relates to an artificial turf comprising artificial grass fibres according to the first aspect, and (preferred) embodiments thereof.

In some preferred embodiments, the artificial turf also comprises artificial grass fibres having a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry. Preferably, the artificial turf comprises bundles of twined artificial grass fibres, wherein the bundles comprise artificial grass fibres according to the invention, as well as optionally artificial grass fibres having a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry.

In a third aspect, the present invention relates to a method for producing an artificial grass fibre, preferably according to the first aspect, and (preferred) embodiments thereof. The method preferably comprises the steps of: melting a polymer or polymer blend, thereby forming a polymer melt; and, extruding the polymer melt through a spinneret comprising one or more cavities, whereby at least one cavity has a cross-section that is asymmetric with regards to reflection symmetry and is asymmetric with regards to rotational symmetry; thereby obtaining an extruded artificial grass fibre.

In some preferred embodiments, the method comprises the step of: heating the extruded artificial grass fibre, preferably for at least 30 seconds at a temperature of at least 50°C.

In a fourth aspect, the present invention relates to a spinneret cavity, preferably configured to perform the method according to the third aspect, and (preferred) embodiments thereof. The spinneret cavity is preferably characterized in that the cross-sectional shape of the spinneret cavity is asymmetric with regards to reflection symmetry and is asymmetric with regards to rotational symmetry.

In a fifth aspect, the present invention relates to a spinneret comprising one or more spinneret cavities according to the fourth aspect, and (preferred) embodiments thereof. The spinneret preferably also comprises one or more spinneret cavities comprising a symmetrical cross- sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry.

In a sixth aspect, the present invention relates to a method for producing an artificial turf according to the second aspect, and (preferred) embodiments thereof.

The independent and dependent claims set out particular and preferred features of the invention. Features from the dependent claims may be combined with features of the independent or other dependent claims as appropriate.

The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 , FIG. 2, and FIG. 3 illustrate microscope images and cross-sectional views of artificial grass fibres not according to the invention since they have reflection symmetry. FIG. 1 illustrates a (symmetrical) unu shape. FIG. 2 illustrates a partially ribbed (symmetrical) trigonal Y shape. FIG. 3 illustrates a fully ribbed (symmetrical) double V or VV shape.

FIG. 4 illustrates cross-sectional views of artificial grass fibres of the propeller type, not according to the invention since they have rotational symmetry of 180° around a rotational axis perpendicular to the page.

FIG. 5, FIG. 6, and FIG. 7 illustrate microscope images and cross-sectional views of artificial grass fibres according to embodiments of the invention, which lack both reflection and rotational symmetry. On the right side of each microscope image, a technical drawing of the shape of spinneret cavity is illustrated. FIG. 5 illustrates a partially ribbed (asymmetrical) double V or Vv shape. FIG. 6 illustrates a fully ribbed (asymmetrical) double C or Cc shape. FIG. 7 illustrates a partially ribbed (asymmetrical) double C or Cc shape.

FIG. 8 illustrates a 3D render of the partially ribbed (asymmetrical) double V or Vv shape illustrated in FIG. 5.

FIG. 9 illustrates a 3D render of the helical shape caused by the natural twisting of the partially ribbed (asymmetrical) double V or Vv shape illustrated in FIG. 5 and FIG.8. FIG. 10 illustrates how a twisted artificial grass fibre illustrated in FIG. 5 and FIG.8 will switch from a wide look (thick side) to a narrow look (thin side) for every 90° twist.

FIG. 11 illustrate how the number of twists may be measured by counting the number of 180° twists.

FIG. 12 illustrates a 3D render of a combination of fibres according to an embodiment of the invention, showing how the cross section at the top of the artificial grass fibres will have a different angle for each blade.

FIG. 13 to FIG. 16 provide microscopic images of an artificial turf according to an embodiment of the invention, showing how the cross section at the top of the artificial grass fibres will have a different angle for each blade.

FIG. 17 illustrates the measured width (in pm) of several artificial grass fibres, compared to the DPF (dtex per filament); comparing asymmetrical fibres according to embodiments of the invention to symmetrical fibres not according to the invention.

FIG. 18 illustrates the measured maximum bending force using a Zwick test (Fmax in N) of several artificial grass fibres, compared to the DPF (dtex per filament); comparing asymmetrical fibres according to embodiments of the invention to symmetrical fibres not according to the invention.

FIG. 19 illustrates the same measured maximum bending force using a Zwick test (Fmax in N) of several artificial grass fibres, compared to the DPF (dtex per filament); showing the effect of asymmetry and ribs.

FIG. 20 illustrates a technical drawing of a spinneret according to an embodiment of the invention.

FIG. 21 illustrates a technical drawing of the shape of a spinneret cavity of the spinneret illustrated in FIG. 20.

FIG. 22 illustrates a technical drawing of a spinneret according to an embodiment of the invention.

FIG. 23 illustrates a technical drawing of the shape of a spinneret cavity of the spinneret illustrated in FIG. 22.

FIG. 24 illustrates a technical drawing of a spinneret according to an embodiment of the invention.

FIG. 25 illustrates a technical drawing of the different shapes of spinneret cavities of the spinneret illustrated in FIG. 24.

DETAILED DESCRIPTION OF THE INVENTION

When describing the invention, the terms used are to be construed in accordance with the following definitions, unless the context dictates otherwise. As used herein, the singular forms "a”, "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a fibre" means one fibre or more than one fibre.

The terms "comprising", "comprises" and "comprised of' as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements, or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of", "consists" and "consists of", which are closed-ended.

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g., 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g., from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

All references cited in the present specification are hereby incorporated by reference in their entirety. In particular, the teachings of all references herein specifically referred to are incorporated by reference.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other, features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art.

The terms described herein, and others used in the specification are well understood to those skilled in the art.

Preferred statements (features) and embodiments, fibres, methods, turfs, spinnerets, and uses of this invention are set herein below. Each statement and embodiment of the invention so defined may be combined with any other statement and/or embodiment unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features or statements indicated as being preferred or advantageous. Hereto, the present invention is in particular captured by any one or any combination of one or more of the below embodiments, with any other statement and/or embodiment.

In a first aspect, the present invention thereto provides an artificial grass fibre for artificial turf, characterized in that the cross-sectional shape of the artificial grass fibre is asymmetric with regards to reflection symmetry and is asymmetric with regards to rotational symmetry.

An artificial grass fibre that is asymmetric with regards to reflection symmetry has a crosssection with essentially no reflection axes. When reflection symmetry is present, it can present for one reflection axis, two reflection axes, three reflection axes, four reflection axes, or more. Typically, at least one reflection axis is perpendicular to the width of the fibre or at least one reflection axis is along the width of the fibre.

An artificial grass fibre that is asymmetric with regards to rotational symmetry has a crosssection with essentially no rotational axes. When rotational symmetry is present, it is typically present for one rotational axis, typically perpendicular to the cross-section and typically at the centre of the cross-section. Typically, the rotational axis is symmetrical with regards to a rotation of 60°, 90°, 120°, or 180°.

The asymmetry that is created this way, results in a different look depending on the viewpoint of the observer, adding much more variation to the overall turf. In addition, the asymmetry that is created this way, results in twisting of the artificial grass fibre, providing a combination of improved strength against wear and tear and adding a further layer of resilience and shock absorption. It has been found that an asymmetrical blade of grass balances both rigidity, flexibility, softness, and look.

In some preferred embodiments, the artificial grass fibre is a monofilament. A monofilament is a single filament of artificial fibre, made by melting (and optionally mixing) polymers, which is extruded through a die, for example a spinneret, to form a long single strand or a bundle of single strands to be tufted together.

The artificial grass fibre, preferably a monofilament, is suitable for use as a grass blade in an artificial turf. The artificial grass fibre is typically tufted and cut into artificial grass blades. The present invention also relates to artificial grass blades made from the artificial grass fibre as described herein. The present invention also relates to the monofilament wound on a bobbin. The term “artificial grass fibres” of an “artificial turf”, herein also sometimes referred to as “synthetic grass fibres”, “artificial yarns”, or synthetic “yarns”, refers to elongated objects which are preferably attached to a primary backing forming an artificial grass field. When tufted through the primary backing, the artificial grass fibres protrude from the upper surface of the primary backing and form the grass surface. The upper surface of the primary backing corresponds to the use side of the artificial turf. Preferably, the artificial grass fibres are arranged in bundles, preferably in bundles of monofilaments. The artificial grass fibres preferably have a dtex from 200-3000, and one bundle may contain 4 to 20 fibres. The artificial grass fibres preferably comprise a polymer or a polymer blend. The artificial grass fibre can be manufactured from materials chosen from the list comprising: polypropylene (PP); any variant of polyethylene (PE) including low density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE)); any variant of co-polymers of PP and PE; polyester (PET); and polyamide (PA); or combinations thereof. Preferably, the artificial grass fibres are manufactured from LLDPE to provide more softness and improved resiliency. In some embodiments, the fibre comprises recycled polymers or has recyclable content.

The artificial grass fibres used in the artificial turf of the present invention may further comprise additives selected from, but not limited to, the group comprising: infrared reflectants, UV stabilisers, fire-retardants, matting agents, luminescent compounds (phosphorescent or fluorescent compounds), fillers (e.g., chalk, talc), colour pigments, processing aid additives (PPA, antioxidants, slip and/or anti-block agents), and/or combinations thereof.

The thickness of the artificial grass fibre preferably ranges from 0.05 mm to 0.50 mm, preferably from 0.7 mm to 0.20 mm, preferably from 0.10 mm to 0.15 mm, for example about 0.13 mm. Furthermore, the width of the artificial grass fibre preferably ranges from 0.5 mm to 2.0 mm, preferably from 0.7 mm to 1.8 mm, preferably from 1.0 mm to 1.5 mm, for example 1.2 mm. The thickness may also vary along the width of the fibre. Due to the low thickness and high width, the fibre provides a very soft touch.

The asymmetrical shape typically causes the artificial grass fibre to twist, creating natural torsion. The torsion is typically visible on a strand of artificial grass fibre, either free-dangling or when wound on a bobbin. In some preferred embodiments, the artificial grass fibre has a helical shape, i.e. forms a single-stranded helix. The helix may be a right-handed helix or a left-handed helix when the turf is viewed from above. Preferably the artificial turf according to the invention comprises a combination of right-handed and left-handed helices.

The naturally twisted fibre results in an improved realistic look of the artificial grass fibre when tufted in an artificial turf. Furthermore, it adds to the resilience, while still feeling soft and bouncy, since the twist provides increased shock absorbing properties and spring. A sports turf made with these artificial grass fibres may thus allow for less injuries. The artificial turf also feels softer to the touch. The fact that the edges are somewhat curved inward by the torsion may also create more softness. The existing haptics/softness mainly due to shape may be further improved by the helix structure as a secondary structure. The helix structure also causes additional variation in the light reflection along the strand, whereby dissipation of light at different angles reduces possible shining effects. The helix also creates bulkiness, meaning that will take more space than a straight fibre. This results in a more open structure. Curved shapes also tend to retain water more easily. The water-retaining curvature may be present on the level of the fibre’s cross-section (CC, VV) as well as on the level of the helix. The helix may also allow to reduce or omit infill.

The twist can be defined by the average distance between each rotation of 180°. The average distance is preferably calculated over 14 measurements on bundles of 8 filaments, cut into pieces of 20 cm length.

In some embodiments, the average distance between each 180° rotation is at least 0.4 cm, for example at least 0.6 cm, for example at least 0.8 cm, for example at least 1.0 cm, for example at least 1.2 cm, for example at least 1 .4 cm.

In some embodiments, the average distance between each 180° rotation is at most 10.0 cm, for example at most 8.0 cm, for example at most 6.0 cm, for example at most 4.0 cm, for example at most 2.0 cm, for example at most 1 .6 cm.

In some embodiments, the average distance between each 180° rotation is at least 0.4 cm and at most 10.0 cm, for example at least 0.6 cm and at most 8.0 cm, for example at least 0.8 cm and at most 6.0 cm, for example at least 1.0 cm and at most 4.0 cm, for example at least 1 .2 cm and at most 2.0 cm, for example at least 1.4 cm and at most 1.6 cm, for example about 1.5 cm.

Width is a measure for the look. Wider artificial grass fibres typically have a more natural look, while too wide looks fake. As demonstrated in the examples, the present invention allows to have wider, realistically looking artificial grass fibres, while simultaneously using less material. Wider fibres allow for more coverage in the tufted end-product. As demonstrated in the examples, the present invention allows to have thinner, realistically looking artificial grass fibres, while simultaneously using less material. Thinner fibres or thinner parts of the fibre become translucent, like natural grass, creating an improved optical effect compared to existing, thicker blades. Furthermore, thinner blades feel softer.

This also results in a more environmentally friendly turf.

The maximal bending force Fmax is a measure of the resilience. The higher the Fmax, the higher the resilience. However, an Fmax that is too high results in a hard feel of the turf. As demonstrated in the examples, the present invention allows to have a combination of strength against wear and tear and improved resilience, without feeling too hard.

As used herein, the term “lengthwise section” refers to a section of the cross-sectional shape, that has a specific geometric shape, which is present over the entire length of the fibre. For example, in a double V shaped fibre, each V may be considered a lengthwise section. Having two lengthwise sections that are different, results in an asymmetrical fibre. Typically each lengthwise section is defined by a conventional geometric shape, such as a V, a C, an S, a Y, a straight element (such as a flange), etc. In some preferred embodiments, the fibre comprises two lengthwise sections with essentially the same geometric shape, but wherein each lengthwise section has one or more different parameters for said same geometric shape. In some preferred embodiments, the fibre comprises two lengthwise sections with a different geometric shape, for example wherein a V and a C are combined.

In some preferred embodiments, at least one parameter differs in at least 10% between each lengthwise section. In some embodiments, the at least one parameter differs in at least 15%, preferably in at least 20%, preferably in at least 25%, preferably in at least 30%, preferably in at least 35%, preferably in at least 40%, preferably in at least 45%, for example in at least 50%. In some embodiments, the at least one parameter differs in at most 100%, preferably in at most 90%, preferably in at most 80%, preferably in at most 70%, preferably in at most 60%, for example in at most 50%.

As an example, the inner angle of one V in a double V-shaped fibre might be 50% larger than the inner angle of the other V. As another example, the arc length of one C in a double C- shaped fibre might be 25% larger than the arc length of the other C.

In some embodiments, one lengthwise section of the artificial grass fibre comprises a larger width compared to the other lengthwise section. In some embodiments, one lengthwise section of the artificial grass fibre comprises a larger thickness compared to the other lengthwise section. In some embodiments, one lengthwise section of the artificial grass fibre comprises a different variation in thickness compared to the other lengthwise section. In some embodiments, one lengthwise section of the artificial grass fibre comprises a larger length compared to the other lengthwise section. In some embodiments, one lengthwise section of the artificial grass fibre comprises a larger inner angle or inner radius compared to the other lengthwise section. This improves water drainage, since for the same total width, a much larger section can be used to drain excess water, for example after rain. This results in an artificial turf that dries more quickly. For example, in an asymmetrical Vv-shaped artificial grass fibre (or a Cc-shaped artificial grass fibre), the larger V lengthwise section (or larger C lengthwise section) will provide improved drainage compared to a symmetrical VV-shaped artificial grass fibre (or CC-shaped artificial grass fibre) with the same overall width. A smaller angled section will provide improved stiffness.

The artificial grass fibres according to the invention may further comprise a backbone nerve, and/or a micro-textured surface (such as grooves and/or ribs) to resemble grass blade nerves to further improve the resemblance to natural grass blades. The artificial grass fibres according to the invention are typically in a green colour, e.g., a unicolour or mixed shades of green and/or other colours (preferably colours that can be found in natural gras, such as yellow, brown, but preferably green). In some embodiments, the artificial grass fibre comprises one or more grooves and/or ribs. As used herein, the term “grooves” refers to lengthwise indentations in the artificial grass fibre. As used herein, the term “ribs” refers to lengthwise raised ridges in the artificial grass fibre. Typically, a succession of grooves will create ribs in between, and vice versa. The grooves and/or ribs preferably extend over the full length of the fibre.

In some embodiments, one lengthwise section of the artificial grass fibre comprises a different number of grooves and/or ribs compared to the other lengthwise section. In some preferred embodiments, one lengthwise section of the artificial grass fibre comprises one or more grooves and/or ribs, while the other lengthwise section comprises no grooves nor ribs. This closely resembles natural grass.

The presence of grooves and/or ribs allows for a different type of light scattering, resulting in an optical effect that resembles real grass. However, the grooves and/or ribs may have an effect on the mechanical properties of the artificial grass fibre, for instance, by improving mechanical stability and wear and tear resistance. By having one or more grooves and/or ribs in one lengthwise section of the artificial grass fibre, and no grooves and/or ribs in the other, an optimum is obtained between optical properties and mechanical properties.

Furthermore, the asymmetry that is created this way, results in a different look depending on the viewpoint of the observer, adding much more variation to the overall turf. In addition, the asymmetry that is created this way, results in twisting of the artificial grass fibre, providing a combination of improved strength against wear and tear and improved resilience.

Preferably, one lengthwise section comprises at least 1 groove and/or rib, preferably at least 2 grooves and/or ribs, preferably at least 3 grooves and/or ribs. Too many ribs however may affect the overall cross-sectional shape of the fibre and may therefore not be desirable. Preferably, one lengthwise section comprises at most 7 grooves and/or ribs, preferably at most 5 grooves and/or ribs, preferably at most 3 grooves and/or ribs. This was found to provide an optimal balance between strength and optical/twisting properties.

The grooves and/or ribs are preferably applied on the highly reflective areas of the fibre, i.e. the parts having a relatively large flat/curved surface area. Therefore, in a Vv-shaped fibre, the grooves and/or ribs are preferably provided on the larger V and/or the V with the widest inner angle. Similarly, in a Cc-shaped fibre, the grooves and/or ribs are preferably provided on the larger C and/or the C with the largest inner radius.

The location (e.g., a slight shift) and number (e.g., 3 vs 2) grooves and/or ribs may be symmetrical while comparing one side of the fibre to the other side or may be asymmetrical while comparing one side of the fibre to the other side. For example, the large C in FIG. 7 shows 3 grooves on the outer side and 2 grooves on the inner side. The large V in FIG. 5 shows the same number of grooves in the same location as either side. In some embodiments, the artificial grass fibre comprises an asymmetrical double V-shaped cross-section, herein referred to as a Vv artificial grass fibre. The cross-section is asymmetric, because one V is different from the other V.

In some preferred embodiments, the artificial grass fibre has an asymmetrical double V shape, wherein one V differs from the other V in at least one, preferably two, more preferably all three aspects below: the inner angle between the legs for each of the V’s is different; the length of the legs for each of the V’s is different; and, one V is ribbed, while the other is not.

The inner angle between the legs for each of the V’s preferably ranges between 90° and 120°. Smaller V legs preferably have a length of from 0.10 mm to 0.50 mm, preferably from 0.15 mm to 0.40mm, preferably from 0.20 mm to 0.30 mm, for example about 0.25 mm.

Larger V legs preferably have a length (LL) of from 0.30 mm to 0.90 mm, preferably from 0.40 mm to 0.80 mm, preferably from 0.50 mm to 0.70 mm, for example about 0.60 mm.

For example, when the legs of the smaller V have a length of 0.25 mm each, and the legs of the larger V have a length of 0.60 mm each, the total length of all sections in the double V will be 1.70 mm. Due to the inner angles, the total width of the cross-section on the other hand will be 1.20 mm.

In some embodiments, the inner angle between the legs for each of the V’s is different. In some embodiments, the angle difference is at least 15%, preferably at least 20%, preferably at least 25%, preferably at least 30%, preferably at least 35%, preferably at least 40%, preferably at least 45%, for example at least 50%. In some embodiments, the angle difference is at most 100%, preferably at most 90%, preferably at most 80%, preferably at most 70%, preferably at most 60%, for example at most 50%. In some embodiments, the inner angle of one V is at least 10° larger than the inner angle of the other V, preferably at least 15° larger, preferably at least 20° larger, preferably at least 25° larger, preferably at least 30° larger, preferably at least 35° larger, preferably at least 40° larger, preferably at least 45° larger.

In some embodiments, the length of the legs (LL) for each of the V’s is different. In some embodiments, the length difference is at least 15%, preferably at least 20%, preferably at least 25%, preferably at least 30%, preferably at least 35%, preferably at least 40%, preferably at least 45%, for example in at least 50%. In some embodiments, the length difference is at most 100%, preferably at most 90%, preferably at most 80%, preferably at most 70%, preferably at most 60%, for example at most 50%.

In some embodiments, one V is ribbed, while the other is not.

In some embodiments, the inner angle between the legs for each of the V’s is different, and the length of the legs for each of the V’s is different, with preferred differences as stated above. In some embodiments, the inner angle between the legs for each of the V’s is different, and one V is ribbed, while the other is not, with preferred differences as stated above.

In some embodiments, the length of the legs for each of the V’s is different, and one V is ribbed, while the other is not, with preferred differences as stated above.

In some embodiments, both V’s are ribbed.

These shapes are typically smoother and wider than those known in the art and increase resilience. V shapes are also typically found in actual grass. The angles/corners provide a clearer visual effect.

In some embodiments, the artificial grass fibre comprises an asymmetrical double C-shaped cross-section, herein referred to as a Cc artificial grass fibre. One C is different from the other C.

The inner angle (IA) for each of the C sections preferably ranges from 90° to 120°.

Smaller C sections typically have an inner radius of from 0.20 mm to 0.80 mm, preferably from 0.30 to 0.70, preferably from 0.40 to 0.60, preferably from 0.45 to 0.65, for example about 0.50 mm.

Larger C sections typically have an inner radius of from 1.50 mm to 3.50 mm, preferably from 2.00 to 3.00, preferably from 2.20 to 2.80, preferably from 2.40 to 2.60, for example about 2.50 mm.

Smaller C sections preferably have an arc length (AL) of from 0.20 mm to 0.80 mm, preferably from 0.30 to 0.70, preferably from 0.40 to 0.60, preferably from 0.45 to 0.65, for example about 0.50 mm.

Larger C sections preferably have an arc length (AL) of from 0.80 mm to 2.00 mm, preferably from 0.90 to 1.70, preferably from 1.00 to 1.50, preferably from 1.10 to 1.30, for example about 1.20 mm.

In some embodiments, the inner radius of each of the C’s is different. In some embodiments, the radius difference is at least 15%, preferably at least 20%, preferably at least 25%, preferably at least 30%, preferably at least 35%, preferably at least 40%, preferably at least 45%, for example at least 50%. In some embodiments, the radius difference is at most 100%, preferably at most 90%, preferably at most 80%, preferably at most 70%, preferably at most 60%, for example at most 50%. In some embodiments, the inner radius of one C is at least 10° larger than the inner radius of the other C, preferably at least 15° larger, preferably at least 20° larger, preferably at least 25° larger, preferably at least 30° larger, preferably at least 35° larger, preferably at least 40° larger, preferably at least 45° larger.

In some embodiments, the arc length of each of the C’s is different. In some embodiments, the length difference is at least 15%, preferably at least 20%, preferably at least 25%, preferably at least 30%, preferably at least 35%, preferably at least 40%, preferably at least 45%, for example at least 50%. In some embodiments, the length difference is at most 100%, preferably at most 90%, preferably at most 80%, preferably at most 70%, preferably at most 60%, for example at most 50%.

In some embodiments, one C is ribbed, while the other is not.

In some embodiments, the inner radius of each of the C’s is different, and the arc length of each of the C’s is different, with preferred differences as stated above.

In some embodiments, the inner radius of each of the C’s is different, and one C is ribbed, while the other is not, with preferred differences as stated above.

In some embodiments, the arc length of each of the C’s is different, and one C is ribbed, while the other is not, with preferred differences as stated above.

In some embodiments, both C’s are ribbed.

These shapes are typically smoother and wider than those known in the art and increase resilience. These shapes also result in improved scattering of light. These shapes also result in improved water retention.

Preferably a Vv shaped yarn is used instead of a Cc shaped yarn. During the extrusion process, the yarns may pass over different sets of godet rolls, whereby some rolls are heated at different temperatures and other rolls are cold. When the yarns enter in contact with the surface of the rolls, a Cc shaped yarn is expected to be in contact in a single point of the surface, or at least in a smaller area compared to the Vv shaped yarns. The sharper angles will lead the Vv shape to lay on one of the legs, which will create a difference in temperature between the two legs (the one that is in direct contact with the roll and the one that is in the air). Since this will be always be either one of the side legs (one leg or the other), the contact with the godet roll remains more or less constant. With the Cc shaped yarn, it was found that the point of contact may vary over the curvature of the shape, and that the area of contact may also be different depending on small variations of tension on the process itself that will push the C shape more or less against the roll, thereby changing its contact area. Therefore, the chances to have a non-controlled variability on the contact of a C-shaped godet roll surface may lead to quality problems. When some bobbins of the complete creel (with C shape yarn) presented this variability, a stripy turf was obtained as a result.

In a second aspect, the present invention relates to an artificial turf, such as an artificial sports field or an artificial lawn, comprising artificial grass fibres according to the first aspect, and (preferred) embodiments thereof. An artificial turf comprises at least a substrate to which one or more fibres according to the invention are tufted. The extruded artificial grass fibres may be provided on the substrate either individually, or in the form of a bundle of fibres which are twined together. The artificial grass fibre according to the invention may be a monofilament. In this embodiment, too, several monofilaments may be combined into bundles by twining, after which each bundle is attached to the substrate.

Artificial turf according to the present invention typically comprises a primary backing. The term “primary backing” as used herein refers to a substrate, preferably a thermoplastic substrate, which can be woven or nonwoven. Preferably, the primary backing is a woven polypropylene backing. The primary backing has an upper and a lower surface, and the primary backing is configured for supporting artificial grass fibres. It is also possible to use a primary backing with a nonwoven layer provided to its upper surface or lower surface. In some embodiments, the fibres are tufted in a double primary backing, with for example fleece or other reinforcement fibres, such as glass fibres. Alternatively, the upper surface of the primary backing can be called a first surface and the lower surface of the primary backing can be called a second surface. As another alternative, the upper surface of the primary backing can be called a use side, and the lower surface of the primary backing can be called a technical side. In some embodiments, the artificial turf comprises a secondary backing, for example a polyurethane (Pll) secondary backing. Whereas the artificial turf strands protrude from the upper side of the primary backing, the secondary backing is applied to the lower side of the primary backing, with the back tufts exposed. A secondary backing provides better tuft lock and a longer product lifetime (improved resistance against moisture/rain and animal excrement). It is also possible to use other technologies, like fusing calendars to (partly) melt the back tuft, where a secondary backing for locking purposes may be omitted.

In case of a Pll secondary backing, the nonwoven primary backing is preferably provided on the upper side (/.e. the use side) of the artificial turf, where its main role is to support the fibres. In case of a traditional latex secondary backing, the nonwoven primary backing is preferably present at the lower surface (/.e. the technical side) of the artificial turf to improve the absorption of the latex, which results in a better tuft lock.

In some embodiments, the nonwoven primary backing is provided by needling fibres or needle felt into the secondary backing.

The artificial grass fibres are preferably tufted or may be woven through the primary backing. Preferably, the fibres are tufted through the primary backing. In some embodiments, the artificial grass fibres may be formed in loop piles or cut piles. The artificial grass fibres are preferably arranged in bundles of fibres. Typically, from 2 to 20 monofilaments are present per bundle, preferably from 4 to 12, preferably from 6 to 10, for example 8 or 9.

The different bundles may be the same in composition, shape, cross-section, resiliency, colour, and/or colour hue. However, to improve the natural look and feel of the artificial turf, the various different bundles may be different in composition, shape, cross-section, resiliency, colour, and/or colour hue. Even more preferably, within one bundle of artificial grass fibres, fibres with different properties may be combined.

The twisting also occurs after the artificial grass fibres have been tufted in an artificial turf, even after twining fibres together into bundles. Due to the variance and randomness on the helix in the tuft, the cross section at the top of the artificial grass fibres is everywhere at another angle. This greatly enhances the realistic look of the turf. It also prevents the artificial grass fibres to lie flat down together, which reduces the formation of bare patches. After tufting, the fibres of the invention create bulkiness and a bulky look in the artificial turf, which also contributes to cushioning (“springs”). The helical shape in the finally tufted grass affects haptics, may feel softer, and provides more scattered light reflection due to the helix.

The artificial turf of the present invention is preferably used for residential lawn, landscaping purposes, terraces, sports fields, and playgrounds.

In some embodiments, the artificial turf comprises a combination of the artificial grass fibres according to the first aspect of the invention, and embodiments thereof, and artificial grass fibres not according to the first aspect of the invention. In some preferred embodiments, the artificial turf also comprises artificial grass fibres having a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry. Preferably, the artificial turf also comprises bundles of twined artificial grass fibres, wherein the bundles comprise artificial grass fibres according to the invention, as well as artificial grass fibres having a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry.

This results in artificial turf with a wide range, both in width and resilience. As a result, such an artificial turf has a realistic look and improved softness and a more random look .

The symmetrical artificial grass fibres may have a cross-section selected from, but not limited to, a rectangular, a propeller-shaped, a diamond-shaped, a round, an elliptical, a multi-lobal (Y, X), a C-shaped, a V-shaped, a W-shaped, an S-shaped, a double V-shaped, a double C- shaped, a unu shaped, a curved C shaped, or an Q-shaped cross-section, and may have dimensions of, e.g., 50-650 pm thickness and 0.5-8.0 mm width.

Fibres of the invention have the advantage that they are typically: very thin (thickness wise); have various thinner parts; more transparent than regular yarns;

- wider than regular yarns; and, demonstrate a twisting effect. Best combinations are therefore made with any other yarns that lack one or more of the above characteristics. For example: combining a straight & wide C-shaped yarn with a twisting and wide Vv shaped yarn; or, combining a straight and small propeller shaped yarn with a twisting and wide Vv shaped yarn.

The contrast with the twisting effect is already advantageous in combination with any straight shape. On top on that, any major contrast on the width, provides added benefits.

Preferably, two or more shapes are combined that show sufficient contrast between the shapes. This may advantageously be achieved by combining two or more yarns with different dtex and different shapes. In some preferred embodiments, a Vv shaped yarn is combined with a propeller shaped yarn; preferably whereby the propeller shaped yarn has a lower dtex than the Vv shaped yarn. For example, Vv 7200 dtex + Propeller 4400 dtex was found to create a more random/non-homogeneous aspect.

For example, since the Vv shaped yarn is much thinner, light goes through the blade (translucence, like natural grass, positively affects the appearance and the colours). The propeller, on the other hand, is thicker and even thicker in the core of the shape and does not have this translucent effect.

Preferably, the symmetrical artificial grass fibres have thicker cross-section, for example a propeller-shaped cross-section, whereby the combination of fibres according to the invention with such symmetrical fibres provides an improved combination of softness and resilience. The symmetrical artificial grass fibres may further comprise a backbone nerve, and/or a microtextured surface (such as grooves and/or ribs) to resemble grass blade nerves to further improve the resemblance to natural grass blades. The symmetrical artificial grass fibres are typically in a green colour, e.g., a unicolour or mixed shades of green and/or other colours.

In a further embodiment, the artificial turf of the present invention may comprise thatch yarns, which extend upward from the upper surface of the primary backing. Thatch yarns are made of monofilaments or slit film tapes which have been textured (curled) and simulate grass roots or moss. Preferably, thatch yarns are inserted together with other fibres in a given bundle of fibres. As such, they are not present as separate rows between the rows of artificial grass fibres. In some embodiments, thatch yarns are inserted in random bundles of artificial grass fibres, or only in certain areas of the artificial turf.

The cross-sectional shape of the cavity decides the cross-sectional shape of the fibre. As used herein, all absolute and relative values with regards to the fibre apply to the cavity and vice versa. Right after extrusion, the extruded artificial grass fibre receives more space, and may swell up a little. Therefore, the dimensions of the final fibre may be slightly different from the dimension of the cavities. Since the dimensions and shapes of the cavities are easier to control, it is preferred that all dimensions and shapes as used herein apply to the cavity of the spinneret.

In addition, extruded filaments might show thinner end edges or any other slight modification of the represented curves of the shape. In some embodiments, the extruded fibre has thinned end edges, which results in improved translucence. The thinned edges are also lighter in weight compared to the thicker part. This provides a more natural look.

In some embodiments, the method comprises the step of: bundling multiple extruded artificial grass fibres from multiple cavities into a bundle.

This improves the helical twist (adds more turns per cm), and all improved properties that follow from the helical twist.

In some embodiments, the method comprises heating the artificial grass fibre for at least 30 seconds, preferably at least 60 seconds, preferably at least 90 seconds.

In some embodiments, the method comprises heating the artificial grass fibre for at most 15 minutes, preferably at most 10 minutes, preferably at most 5 minutes.

In some embodiments, the method comprises heating the artificial grass fibre for at least 30 seconds and at most 15 minutes, preferably at least 60 seconds and at most 10 minutes, preferably at least 90 seconds and at most 5 minutes, for example about 120 seconds.

In some embodiments, the method comprises heating the artificial grass fibre at a temperature of at least 50°C, preferably at least 60°C, preferably at least 70°C.

In some embodiments, the method comprises heating the artificial grass fibre at a temperature of at most 100°C, preferably at most 90°C, preferably at most 80°C. In some embodiments, the method comprises heating the artificial grass fibre at a temperature of at least 50°C and at most 100°C, preferably at least 60°C and at most 90°C, preferably at least 70°C and at most 80°C, for example about 75°C.

The present invention is related to the asymmetry of the cross section. This asymmetry is created by a specific design of the extrusion spinneret. Due to this asymmetry, the fibre behaves differently in the end-product (artificial grass turf) than other fibres. This specific behaviour can be specified as a torsion of the fibre, which creates a natural aspect.

As used herein, the term “spinneret” refers to a type of die principally used in fibre manufacture. It is usually a metal plate with many small cavities (spinneret cavities) through which a melt is pulled and/or forced.

Therefore, in a fourth aspect, the present invention relates to a spinneret cavity, preferably configured to perform the method according to the third aspect, and (preferred) embodiments thereof. The spinneret cavity is preferably characterized in that the cross-sectional shape of the spinneret cavity is asymmetric with regards to reflection symmetry and is asymmetric with regards to rotational symmetry. Preferred embodiments of the artificial grass fibre are also preferred embodiments of the spinneret cavity, particularly regarding shape and dimensions. In a fifth aspect, the present invention relates to a spinneret comprising one or more spinneret cavities according to the fourth aspect, and (preferred) embodiments thereof. Spinnerets with multiple cavities allow for several artificial grass fibres to be bundled and tufted together and create a more randomised and natural look.

Preferably, the spinneret comprises multiple different spinneret cavities according to the fourth aspect, and (preferred) embodiments thereof. Such spinnerets allow for several twisting artificial grass fibres with variable twists and looks to be bundled and tufted together, which creates a more randomised and natural look, but also improves resilience and strength.

The spinneret preferably also comprises one or more spinneret cavities comprising a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry. Such spinnerets allow for several twisting artificial grass fibres to be bundled and tufted together with regular artificial grass fibres, which creates a more randomised and natural look, but also improves resilience and strength.

The method preferably comprises the steps of: providing artificial grass fibres according to the first aspect of the invention, and (preferred) embodiments thereof, or performing the method according to the third aspect of the invention, and (preferred) embodiments thereof; providing a primary backing; and, tufting through said primary backing piles comprising the artificial grass fibres.

In some embodiments, the method comprises the steps of: bundling multiple artificial grass fibres according to the first aspect of the invention, and (preferred) embodiments thereof, or obtained by the method according to the third aspect of the invention, and (preferred) embodiments thereof, into bundles; and, tufting through said primary backing piles comprising the bundles of artificial grass fibres.

In some embodiments, the method comprises the steps of: bundling multiple artificial grass fibres according to the first aspect of the invention, and (preferred) embodiments thereof, or obtained by the method according to the third aspect of the invention, and (preferred) embodiments thereof, with artificial grass fibres having a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry, into bundles; and, tufting through said primary backing piles comprising the bundles of artificial grass fibres.

The step of tufting piles typically comprises looping the piles with loopers into loop-piles. Optionally, the loop-piles can be cut into cut-piles or tufts with knives. In some embodiments, the method preferably comprises the step of: cutting the piles into tufts.

Non-cut piles look less natural but have improved damping properties. For example, when damping properties are important, such as in a playground, higher fibres may be cut into tufts, while shorter fibres may be left as piles.

EXAMPLES

The following examples serve to merely illustrate the invention and should not be construed as limiting its scope in any way. While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the scope of the invention.

Example 1 - Shapes FIG. 1 , FIG. 2, and FIG. 3 illustrate microscope images and cross-sectional views of artificial grass fibres not according to the invention. These shapes clearly have reflectional symmetry, with the reflection axis shown. FIG. 1 is referred to herein as a unu shape. FIG. 2 is referred to herein as a partially ribbed (symmetrical) trigonal Y shape. FIG. 3 is referred to herein as a fully ribbed (symmetrical) double V or VV shape.

FIG. 4 illustrates cross-sectional views of artificial grass fibres of the propeller type, not according to the invention. These shapes clearly have rotational symmetry of 180° around a rotational axis perpendicular to the page.

FIG. 5, FIG. 6, and FIG. 7 illustrate microscope images and cross-sectional views of artificial grass fibres according to the invention. On the right side of each microscope image, a technical drawing of the shape of spinneret cavity is illustrated. These shapes clearly lack both reflection and rotational symmetry.

FIG. 5 is referred to herein as a partially ribbed (asymmetrical) double V or Vv shape. The asymmetry is caused by three differences: the inner angle between the legs for each of the V’s is different; the length of the legs for each of the V’s is different; and, one V is ribbed, while the other is not.

The two lengthwise sections are illustrated by brackets (LS). These two distinct V-shaped sections are visible in the cross-sectional shape and are present over the entire length of the fibre. The thickness of the fibre (T) and the length of one leg (LL) are also indicated. The total length is the sum of the four lengths of the four legs (LL), which will be longer than the total width (W) of the fibre, due to the inner angles.

FIG. 6 is referred to herein as a fully ribbed (asymmetrical) double C or Cc shape. The asymmetry is caused by two differences, since both sections are fully ribbed: the inner radius of each of the C’s is different; and, the arc length of each of the C’s is different.

The two lengthwise sections are illustrated by brackets (LS). These two distinct C-shaped sections are visible in the cross-sectional shape and are present over the entire length of the fibre. The arc length (AL) and inner angle (IA) of one of the C sections are also indicated. The total length is the sum of the two arc lengths (AL) of the two C sections, which will be longer than the total width (W) of the fibre, due to the curvature.

FIG. 7 is referred to herein as a partially ribbed (asymmetrical) double C or Cc shape. The asymmetry is caused by three differences: the inner radius of each of the C’s is different; the arc length of each of the C’s is different; and, one C is ribbed, while the other is not. FIG. 8 is a 3D render of the partially ribbed (asymmetrical) double V or Vv shape illustrated in

FIG. 5.

Example 2 - Twisting of the artificial grass fibre

As shown in the 3D render of FIG. 9, the asymmetry of the Vv shaped artificial grass fibre of FIG.5 and FIG.8 creates a natural twist, thereby creating a helical shape. This twist gives the final grass blade a more natural look and provides additional resilience.

Looking from above, a twisted artificial grass fibre will switch from a wide look (thick side) to a narrow look (thin side) for every 90° twist, as illustrated in FIG. 10. The number of twists can be measured; for example the arrows in FIG. 11 illustrate the 180° twists. The number of 90° twists will be twice the number of 180° twists.

Table 1 illustrates the number of times the Vv artificial grass fibre changed its angle 180° for strands of 20 cm artificial grass fibre, showing a lot of variance between the strands. The twists were counted before and after a heating step (2 min at 75°C), which clearly increased the number of twists. There seemed to be no uniform direction to the twist, there was a great degree of randomness.

180° twists Before heating After heating

Average 3.85 8.68

Max 7 15

Min 2 1

Table 1

The twisting also occurs after the artificial grass fibre has been tufted and cut in an artificial turf. Due to the variance and randomness on the helix in the tuft, the cross section at the top of the artificial grass fibres will have a different angle for each blade, as illustrated in FIG. 12 to FIG. 16. FIG. 12 illustrates a 3D render, while FIG. 13 to FIG. 16 provide microscopic images of an actual artificial turf. This twist results in an improved realistic look of the artificial grass fibre when tufted in an artificial turf. Furthermore, it adds to the resilience, while still feeling soft and bouncy, since the twist provides increased shock absorbing properties. A sports turf made with these artificial grass fibres may thus allow for less injuries. The artificial turf also feels softer to the touch. The filaments opening more and in different directions may cover more air area, thereby creating a kind of close layer.

Example 3 - Width of the artificial grass fibre FIG. 17 illustrates the measured width (in pm) of several artificial grass fibres, compared to the DPF (dtex per filament, defined as the weight in grams of 10 000 meters of individual filament); comparing asymmetrical fibres according to the invention to symmetrical fibres not according to the invention. It is clear that the artificial grass fibres according to the invention are wider for the same DPF (dtex per filament), or in the inverse, have a lower DPF for the same width. This allows obtaining the same width with less material. This also increases the softness. This also increases coverage on the final tufted end-product.

Example 4 - Resilience of the artificial grass fibre

FIG. 18 illustrates the measured maximum bending force using a Zwick test (Fmax in N) of several artificial grass fibres, compared to the DPF (dtex per filament); comparing asymmetrical fibres according to the invention to symmetrical fibres not according to the invention. Fmax stands for the maximum bending force which must be applied when bending the fibres to an angle of 90° and can be used as an indicator of resilience. FIG. 19 illustrates the same measured maximum bending force using a Zwick test (Fmax in N) of several artificial grass fibres, compared to the DPF (dtex per filament); showing the effect of asymmetry and ribs.

It is clear that the artificial grass fibres according to the invention have improved resilience for the same DPF (dtex per filament), or in the inverse, have a lower DPF for the same resilience. This allows obtaining the same resilience with less material, or improved resilience with the same amount of material.

The tests performed in FIG. 18 and FIG. 19 do not consider the twisting motion of the fibres caused by the asymmetry. This twisting motion adds a further layer of resilience and shock absorption.

Zwick test:

1. During sample preparation, the filaments are wound around a metal sample holder. 32 filaments are used in total.

2. Once the filaments have been correctly wound around the sample holder, the top side is stuck with tape, such that they can be cut right above the tape.

3. At the bottom side, the filaments are cut along the edge of the metal sample holder.

4. The filaments are stuck to each other by sticking tape on the other side as well.

5. The distance between loadcell and sample is set to 3 mm.

6. The sample is clamped in the centre of the loadcell, such that the tape does not protrude from below the clamps.

7. The data are entered in the software, and the test commences by performing 30 bending motions under a 90° angle.

8. The test stops automatically, after which the sample may be removed. Example 5 - Spinneret

FIG. 20 illustrates a technical drawing of a spinneret according to an embodiment of the invention. The spinneret comprises multiple spinneret cavities with a shape as illustrated in FIG. 21 . When polymer melt is extruded through this spinneret, multiple strands will be formed with the asymmetrical partially ribbed Cc shape of FIG. 7. These strands can be combined into a bundle of fibres, which can be tufted together in an artificial turf.

FIG. 22 illustrates a technical drawing of a spinneret according to an embodiment of the invention. The spinneret comprises multiple spinneret cavities with a shape as illustrated in FIG. 23. When polymer melt is extruded through this spinneret, multiple strands will be formed with the asymmetrical partially ribbed Vv shape of FIG. 5 and FIG. 8. These strands can be combined into a bundle of fibres, which can be tufted together in an artificial turf. It is noted that FIG. 8 is a render based on the spinning cavity design: extruded filaments might show thinner end edges or any other slight modification of the represented curves of the shape, as a result of the extrusion process itself, where such a faithful/sharp representation of the original cross-sectional area of the spinneret cavity is difficult to obtain in an extruded filament.

FIG. 24 illustrates a technical drawing of a spinneret according to an embodiment of the invention. The spinneret comprises multiple spinneret cavities with different shapes (labelled B, C, D, and E) as illustrated in FIG. 25, combining asymmetrical shapes with symmetrical shapes. When polymer melt is extruded through this spinneret, multiple strands will be formed with the different cross-sectional shapes. These strands can be combined into a bundle of fibres, comprising the combination of cross-sectional shapes, which can be tufted together in an artificial turf.

Example 6 - Combinations

Due to the improved width and resilience properties, new combinations with existing fibres can be made, for example with fibres that have inferior properties. In the combination of fibres within one bundle forming a tuft, the goal is to achieve as wide a range as possible of width and resilience, so the combined tuft has the most natural look and resilience/softness properties. It was found that due to the new width and resilience properties, new and more varied combinations could be made.

The combination of 4 shapes as illustrated in FIG. 25, and formed by the spinneret illustrated in FIG. 24, leads to a combined bundle with its properties correspondingly combined, and improved ranges compared to combinations of the prior art. These shapes have a higher DPF, and it can be expected will have a higher width (for a wider yarn and similar shape, the yarn will have a higher DPF). The maximum range in width between these 4 shapes is about 500pm (compared to Y/propeller combination of fibres which has a width range of 300pm and reinforced C/nerved oval combination of fibres which has a width of 200pm). The maximum range in Fmax between these 4 shapes is about 0.7 N (compared to Y/propeller combination of fibres and reinforced C/nerved oval combination of fibres, which both have an Fmax range of about 0.2 N).

Claims

1. Artificial grass fibre for artificial turf, characterized in that the cross-sectional shape of the artificial grass fibre is asymmetric with regards to reflection symmetry and is asymmetric with regards to rotational symmetry.

2. Artificial grass fibre according to claim 1 , wherein the artificial grass fibre is a monofilament.

3. Artificial grass fibre according to any one of claims 1 or 2, whereby the artificial grass fibre has a helical shape, preferably wherein the helical shape has an average distance between each 180° rotation of at least 0.4 cm and at most 10.0 cm.

4. Artificial grass fibre according to any one of claims 1 to 3, wherein the fibre consists of two lengthwise sections, wherein one lengthwise section of the artificial grass fibre comprises a different shape and/or dimensions compared to the other lengthwise section of the artificial grass fibre.

5. Artificial grass fibre according to claim 4, wherein the fibre comprises two lengthwise sections with essentially the same geometric shape, but wherein each lengthwise section has one or more different parameters for said same geometric shape.

6. Artificial grass fibre according to claim 5, wherein at least one parameter differs in at least 10% between each lengthwise section.

7. Artificial grass fibre according to any one of claims 4 to 6, wherein one lengthwise section of the artificial grass fibre comprises one or more grooves and/or ribs, while the other lengthwise section comprises no grooves nor ribs.

8. Artificial grass fibre according to any one of claims 1 to 7, wherein the artificial grass fibre has an asymmetrical double V shape, wherein one V differs from the other V in at least one, preferably two, more preferably all three aspects below: the inner angle between the legs for each of the V’s is different; the length of the legs for each of the V’s is different; and, one V is ribbed, while the other is not.

9. Artificial grass fibre according to any one of claims 1 to 7, wherein the artificial grass fibre has an asymmetrical double C shape, wherein one C differs from the other C in at least one, preferably two, more preferably all three aspects below: the inner radius of each of the C’s is different; the arc length of each of the C’s is different; and, one C is ribbed, while the other is not.

10. Artificial turf comprising artificial grass fibres according to any one of claims 1 to 9.

11. Artificial turf according to claim 10, wherein the artificial turf also comprises artificial grass fibres having a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry; preferably wherein the artificial turf comprises bundles of twined artificial grass fibres, wherein the bundles comprise artificial grass fibres according any one of claims 1 to 9, as well as artificial grass fibres having a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry.

12. Method for producing an artificial grass fibre, preferably according to any one of claims 1 to 9, the method comprising the steps of: melting a polymer or polymer blend, thereby forming a polymer melt; and, extruding the polymer melt through a spinneret comprising one or more cavities, whereby at least one cavity has a cross-section that is asymmetric with regards to reflection symmetry and is asymmetric with regards to rotational symmetry; thereby obtaining an extruded artificial grass fibre.

13. Method according to claim 12, the method comprising the step of: heating the extruded artificial grass fibre, preferably for at least 30 seconds at a temperature of at least 50°C.

14. Spinneret cavity, preferably configured to perform the method of any one of claims 12 or 13, characterized in that the cross-sectional shape of the spinneret cavity is asymmetric with regards to reflection symmetry and is asymmetric with regards to rotational symmetry. Spinneret comprising one or more spinneret cavities according to claim 14, and optionally one or more spinneret cavities comprising a symmetrical cross-sectional shape with regards to reflection symmetry and/or a symmetrical cross-sectional shape with regards to rotational symmetry.