EP0728869A1 - Under layer, especially for artifical grass - Google Patents

Abstract

The underlay, esp. for synthetic turf on a sports ground, is made from a mixt. of closed-cell foam rubber and two- or three-dimensional particles of ground recycled rubber with rough surfaces, the mixt. being held together by a binding agent. The ground recycled rubber can be obtd. from a hammer mill, and the binding agent is a polyurethane-based polymer. The thickness of the underlay is between 8 and 14 mm, and pref. 10 mm, and its density is of the order of 0.5.

Description

The present invention relates to an underlay, in particular for synthetic grass. It applies in particular to the construction of sports fields.

To avoid the costly maintenance of natural grass, linked to bad weather and the use made of it, in particular on sports fields, synthetic coverings with the appearance of grass are used more and more often.

A commonly used solution consists of laying synthetic grass slabs weighted with sand on base layers such as concrete or bituminous coated slabs.

These base layers have the disadvantage of not reflecting the intrinsic properties of natural grass such as high flexibility or drainage qualities.

The object of the invention is to provide a sub-layer which makes it possible to overcome these drawbacks, that is to say which is flexible, draining and resistant to traction, and this with a low cost price.

To this end, the subject of the invention is a sub-layer, in particular for synthetic grass, characterized in that it comprises a mixture of closed-cell rubber foam and two- or three-dimensional particles of crushed recycled rubber, this mixture being agglomerated by a binder.

• les particules de caoutchouc recyclé broyé présentent des aspérités sur leurs surfaces ;
• les particules bi- ou tridimensionnelles de caoutchouc recyclé broyé comprennent des particules de caoutchouc étiré obtenues par broyage dans un broyeur à marteaux ;
• le liant est un polymère à base de polyuréthanne ;
• l'épaisseur de la sous-couche est comprise entre 8 et 14 mm, et est de préférence égale à 10 mm ; et
• la densité de la sous-couche est de l'ordre de 0,5.

The underlay for synthetic grass according to the invention may include one or more of the following characteristics:

• the particles of crushed recycled rubber have roughness on their surfaces;
• the two- or three-dimensional particles of crushed recycled rubber include particles of drawn rubber obtained by grinding in a hammer mill;
• the binder is a polyurethane-based polymer;
• the thickness of the sub-layer is between 8 and 14 mm, and is preferably equal to 10 mm; and
• the density of the sublayer is of the order of 0.5.

An exemplary embodiment of the invention will now be described.

The underlay for synthetic grass according to the invention is composed of two constituents based on recycled rubber agglomerated by a binder.

A first component is closed cell rubber foam, of the type used in high-end motor vehicle seats. This foam is ground and has high flexibility qualities.

Particles of stretched recycled rubber constitute the second constituent. These particles are obtained by a grinding process in a hammer mill known per se.

The stretched rubber particles have a body of two- or three-dimensional shape, the surfaces of which have asperities. They are longer than wide; their length is of the order of 0.5 to 8 mm, and they pass through a sieve with 8 mm openings. These stretched particles have properties similar to those of springs, that is to say that they have a good resistance to traction and depression and are moreover very flexible, in any case clearly more than others. types of recycled rubber particles, such as one-dimensional "needles" obtained by scraping used tires with a rotating wire brush.

The binder used here is for example a polyurethane prepolymer.

This mixture of three constituents can be shaped by molding or extrusion in the form of a layer 60 to 80 mm thick which is then split into layers of thickness between 8 to 14 mm, and preferably 10 mm about. These layers are then rolled up in rolls. The layers obtained have a density of the order of 0.5.

Thanks in particular to the uneven surfaces of the stretched rubber particles, the underlay obtained contains a certain amount of vacuum which allows it to be draining.

On the other hand, such an underlay has both high mechanical strength and high flexibility, since the foam is very flexible and the stretched particles are resistant to traction and sinking and are also also flexible. .

The underlay thus obtained thus has three essential characteristics required for a sports field: to be at the same time resistant, flexible and draining.

In addition, the process for obtaining the drawn particles is of low cost, in particular because the hammer mills do not need to be sharpened, and because it suffices to use a proportion relatively low foam, which is the relatively expensive constituent.

In addition, the handling of the rollers intended to form the underlay is easy since they are of low density; they are rolled out on a foundation layer made of porous materials such as porous concrete or a draining bituminous mix.

The undercoat according to the present invention can be applied to other embodiments than those sports grounds, such as children's play areas.

Claims (6)

Underlay, in particular for synthetic turf, characterized in that it comprises a mixture of closed-cell rubber foam and two- or three-dimensional particles of crushed recycled rubber, this mixture being agglomerated by a binder. Underlayment according to claim 1, characterized in that the particles of crushed recycled rubber have roughness on their surfaces. Underlay according to claim 1 or 2, characterized in that the two- or three-dimensional particles of crushed recycled rubber comprise particles of drawn rubber obtained by grinding in a hammer mill. Underlay according to any one of claims 1 to 3, characterized in that the binder is a polyurethane-based polymer. Underlay according to any one of claims 1 to 4, characterized in that the thickness of the underlay is between 8 and 14 mm, and is preferably equal to 10 mm. Underlay according to any one of claims 1 to 5, characterized in that the density of the underlay is of the order of 0.5.