ARTIFICIAL TURF

The present invention relates to an artificial turf comprising a ground fabric made from synthetic ground warp yarns and synthetic weft yarns and a number of plastic blades of grass protruding from the ground fabric.

Artificial turf is being used increasingly often as a replacement for natural turf because:

- the climatic conditions are not always suitable for natural turf; - the load to which the natural turf is subjected (during sports events) damages the playing field, which makes it necessary to leave considerable intervals before using the playing field again; natural turf requires a lot of care and attention.

It is well known to produce artificial turf in which plastic fibers (grass blades) are connected to a carrier material in which the plastic grass blades preferably protrude from the carrier material at right angles. The plastic grass blades are generally hard and smooth plastic fibers, such as polyolefins (polyethylene, polypropylene and mixtures) or polyamides.

Usually, the carrier material is a textile cloth through which the plastic grass blades are tufted. This means that a plastic grass blade is pushed through the cloth by means of a needle to form a loop. On the other side of the textile cloth, a hook takes over the loop which has been produced and takes this loop to the desired level. The loop is then usually cut through, resulting in the formation of two upright grass blades.

With the known manufacturing techniques for producing artificial turf, the plastic blades of grass have to be secured in the carrier material subsequently by applying a coating in order to achieve a satisfactory pile fixation. If the plastic blades of grass consist of a bundle of individual monofilaments, the coating also has to secure the

various filaments with respect to one another in order to achieve a satisfactory pile fixation due to the smoothness of the individual filaments.

However, applying such coatings has various drawbacks:

high cost price; additional operation required on an additional and rather large device; expensive after-treatment of the resulting artificial turf at a temperature which is generally 8O ⁰ C or higher in order to dry the coating. Such an after- treatment will adversely affect the properties of the plastic blades of grass and result in a significant shrinking of this material (shrinkage of up to 10%); impact on the environment, in particular as a result of the applied coating

(e.g. bitumen, latex) leaching out during use, and at the end of service life of the turf.

It is an object of the invention to provide an artificial turf in which the plastic blades of grass are secured sufficiently without requiring the application of a coating on the back of the ground fabric.

The object of the invention is achieved by providing an artificial turf comprising a ground fabric made from synthetic ground warp yarns and synthetic weft yarns and a number of plastic blades of grass protruding from the ground fabric in which said turf, as a result of the weave structure, has a pile fixation of at least 15 N. More particularly, the turf has a pile fixation of at least 20 N, preferably 25 N, as a result of the weave structure.

According to a preferred embodiment of the artificial turf, said turf, as a result of the weave structure, has a pile fixation of at least 30 N, more particularly of at least 40 N. The pile fixation values are measured according to the standardized method according to ISO 4919 (1978).

With a more preferred artificial turf according to the present invention, the plastic blades of grass protruding from the ground fabric are tied up in the ground fabric by a W weave in which the plastic blade of grass is tied up at least twice over an intermediate weft yarn between two upright legs of a pile burl. Tying up the plastic blades of grass several times between the upright pile legs of a pile burl has a very positive effect on the securing of this plastic blade of grass. Some preferred weaves are: 5/12 W, 7/16 W, 9/20 W as well as 3/6 W, 5/10 W and 7/12 W. For example with a 5/12 W weave structure, one pile burl with two pile legs is formed every 12 weft yarns and wound around 5 weft yarns: the first pile leg passes underneath a weft yarn, then over a subsequent weft yarn, underneath a subsequent weft yarn, again over the next weft yarn and then again underneath the next weft yarn, ultimately protruding from the fabric and forming the second pile leg of the pile tuft. The expression "tying up the plastic blades of grass over a weft yarn between the pile legs" is understood to mean that the plastic blade of grass winds itself around a weft yarn which is situated on the side of the artificial turf from which the plastic blades of grass protrude. In said 5/12 W weave, each pile burl does this twice.

In the case of a particular artificial turf according to the present invention, the plastic blades of grass protruding from the ground fabric have a density of at least 1000 tex. Preferably, said plastic blades of grass have a density of at least 1200 tex, more preferably at least 1400 tex. In particular, the plastic blades of grass protruding from the ground fabric have a density of at least 1600 tex, more preferably of at least 1800 tex and most preferably 2000 tex. High-density pile warp yarns are held more firmly in the ground fabric, which improves the securing and fixation of the pile.

According to an advantageous embodiment of the artificial turf according to the invention, the plastic blades of grass protruding from the ground fabric are monofilament yarns which comprise at least six filaments. Preferably, these monofilament yarns comprise 8 filaments, more preferably 10 filaments and in a most preferred embodiment, the monofilament yarns comprise 12 filaments. Thus, a 1600 tex monofilament yarn can comprise 8 filaments of 200 tex each.

In a preferred embodiment of the artificial turf, the plastic blades of grass protruding from the ground fabric protrude at least 20 mm above the ground fabric. Preferably, the plastic blades of grass protrude 25 mm above the ground fabric, more preferably 30 mm. In a particular embodiment of the turf, the plastic blades of grass protrude 40 mm, more preferably 50 mm, still more preferably 60 mm and most preferably 65 mm, above the ground fabric.

In a more preferred artificial turf according to the present invention, said ground fabric comprises binding and tension warp yarns and the protruding plastic blades of grass are pile warp yarns. The binding and tension warp yarns are preferably synthetic yarns, such as for example polypropylene, polyethylene or polyester. The pile warp yarns are in particular synthetic yarns made from, for example, polypropylene, polyethylene or polyamide.

According to a particularly preferred embodiment of the artificial turf according to the invention, said turf has a fabric density of at least 120 warp yarn portees per meter, more particularly 166 warp yarn portees per meter, in the weft yarn direction. Preferably, the turf has a fabric density of 200 warp yarn portees per meter, in particular 240 warp yarn portees per meter, in the weft yarn direction.

Warp yarn portee is understood to mean a combination of binding, tension and pile warp yarns which are situated in the same reed tooth, which combination repeats in the weft yarn direction.

Preferably, each warp yarn portee comprises two tension warp yarns per ground fabric. Furthermore, each warp yarn portee preferably comprises two binding warp yarns per ground fabric and at least one pile warp yarn.

According to a first, more particularly preferred embodiment of the artificial turf according to the invention, said two tension warp yarns are situated on either side of

at least one pile warp yarn for each warp yarn portee. Preferably, the binding warp yarns are outside the latter, in other words between two tension warp yarns which do not have any pile warp yarns between them. This has the advantage that the tight tension warp yarns hold the pile warp yarns firmly in position in the weft yarn direction which results in a clamping effect on the pile warp yarns. This contributes to a good pile fixation.

According to a second, more preferred embodiment of the artificial turf according to the invention, the pile warp yarns are situated between said two tension warp yarns for each warp yarn portee.

According to a second, more preferred embodiment of the artificial turf according to the invention, only pile warp yarns are situated between said two tension warp yarns for each warp yarn portee.

In a preferred embodiment of the artificial turf according to the invention, said turf has a weft yarn density of at least 3 weft yarns per cm, more preferably of 4 weft yarns per cm. In a particular embodiment, said turf has a weft yarn density of 4.6 weft yarns per cm, more preferably of 5.3 weft yarns per cm and most preferably of 6 weft yarns per cm.

According to a particularly preferred embodiment of the artificial turf according to the invention, said turf, in addition to the grass blade-forming pile warp yarns, also comprises supporting pile warp yarns. The supporting pile warp yarns are pile warp yarns which shrink after having been cut through and form a base layer on the ground fabric which: support grass blade-forming pile warp yarns; form a shock-absorbing layer, as a result of which they can completely or partially replace the filling of the artificial turf; - give stability to the ground fabric.

According to yet another preferred embodiment of the artificial turf according to the invention, said turf, in addition to the grass blade-forming pile warp yarns and/or supporting pile warp yarns, also comprises filler yarns. Filler yarns are understood to be warp yarns which extend mainly in the ground fabric and protrude from the fabric virtually without forming pile. One of the characteristics of filler yarns is the fact that they increase the stability of the artificial turf and, by their presence in the ground fabric of the artificial turf, limit the free space for the pile warp yarn, thus further improving the pile fixation. The expression "the filler yarns extend mainly in the ground fabric" is understood to mean that they extend mainly or solely between the layers of weft yarns. In some cases, they may be tied up from time to time over one of these weft yarns in order to be attached to the fabric to a sufficient degree.

The artificial turf is preferably woven according to a face-to-face weaving method. According to this face-to-face weaving method, a top and a bottom fabric are woven on a face-to-face weaving device.