Prior Art It is known to press together or mould rubber waste to a porous material which can be used for sound absorption or insulation. See SE-A-9603951-6. The present invention relates to a development of this idea and involves a new method for producing units of decomposed rubber waste from for example tyres.

Brief Description of the Invention Thus, the invention relates to a method for producing sound absorbing, vibration-damping and/or heaticold insulating units of rubber waste from for example tyres. The invention is characterised in that the rubber waste is decomposed to a desired degree and thereafter mixed with a binder, after which the mixture is formed to said units and is solidified. The binding agent has to be of the type such that the units are elastic even after the solidification.

As the binding agent, a bicomponent glue can be used, which is non-rigid or "soft" even after cold hardening. The binding agent should not be dangerous for the users. A bicomponent polyurethane glue with a hardener is an example of a suitable binding agent.

The units produced according to the present invention can, for example, be used as noise protecting walls along roads, vibration dampers on roads or as insulating units in buildings. The units according to the present invention are very advantageous since they are easily formed in the desired dimensions and shapes, even in situ, and since they are modified and machined and moved easily after the solidification.

At present, excavated material, wood or concrete are preferably used as noise protection materials along roads and railways. An essential advantage when using the units according to the invention is that a considerably better sound insulation is obtained than by screens of concrete or wood. Sound measurements have indicated that the only comparable material, as far as the sound absorption power is concerned, is plastic foams or mineral wool, but these are not suitable materials outdoors used as noise protecting screens. A special advantage of the units according to the invention applied as noise protecting screens is, that they absorb the sound and don't just reflect it.

The units are very cheap to produce as well. In comparison with extensive constructions when building up embankments, the costs can be reduced substantially, at the same time as a more effective result is obtained.

When the units are used as noise protecting screens, another advantage is that they can be produced in situ, for example by using a usual concrete mixer, moulds and a lorry with a mobile crane. A special big crane to place the units is not required.

Another advantage of the invention is the arrangements of the holders of the units, which are labour-saving, material saving and which can be adapted in different ways.

A further advantage of the units according to the invention, for example when they are used as noise protecting screens, is that they are easily removable or replaceable. The base of the noise protecting screens is removable, or there are

drilled holes in the ground which need not be removed. The environment of the road can be re-established in a simple way in comparison with the extensive excavation required in the case of constructed embankments.

An additional advantage of the units is that they are produced of waste which harms the environment, the units according to the invention taking care of such materials contributing towards a better environment.

Description of Embodiment Examples The invention is described below by embodiment examples indicated in the drawings, where Figure 1 shows a noise protecting screen according to the invention, Figure 2 shows another embodiment example of a noise protecting screen according to the invention, Figure 3 shows a noise protecting screen according to the invention arranged on an existing noise protecting screen of wood, for example, Figure 4 shows a diagram concerning the absorption factor of different materials, Figure 5 shows a diagram concerning the reduction factor of rubber material according to the invention.

Figure 1 shows a unit 1 produced according to the invention and intended to be used as a noise protecting screen along a road. The screen is produced of old decomposed tyres mixed with a binding agent, especially a bicomponent glue.

The glue should have a curing time which is long enough to get the unit completed, produced in situ, including the holders, before the material is solidified. The unit can be put in its position before it is completely solidified.

If noise protecting screens are produced in situ, usual concrete mixers can be used for the mixing of the decomposed rubber material with a binding agent.

The mixture is poured out into a mould, where appropriate after adding of the other component, and is solidified, cold-cured, in the mould. By choosing a bicomponent glue with a setting time which is long enough, there is time enough to arrange holders and lifting arrangements. The bicomponent glue is preferably such that the completed unit is "softened" in a flexible way. The result implies better absorption qualities and a unit which is more easily shaped without getting cracks.

There are means 2 arranged in an appropriate way to form holders for the prepared unit. These means can consist of two or more metal tubes imbedded in the material in the mould. The outer end of the tube (tubes) is on the same level as a face 3 of the element. The unit is placed by means of separate rods pushed into the tubes, the other end of each rod being pushed into a drilled hole in the ground or in a tube which is fixed in a foundation or in the ground.

The means 2 can also consist of rods, the one end of which protruding outside the face 3, the rods being placed in holes arranged in the position where the unit is to be located.

Other means to arrange the element are useful as well, for example stabilising frames, hanging means, supports, console means or the like.

It is also appropriate to arrange means for lifting the completed unit. These means can consist of a hook, a lifting eye bolt 4 or the like, making the lifting of the unit easier.

The unit 1 can consist of a noise protecting screen adapted to be suspended or arranged in another way on an existing noise protecting screen 5 of concrete, for example, or of wood, to improve the sound absorption, see Figure 3. In this case the holder can consist of a suspension device 6 or the like, which co-operates with tubes 7 imbedded in the unit.

Figure 4 shows a diagram of the absorption factor of the unit according

to the invention, the unit having a thickness of about 30 cm.

Figure 5 shows the reduction factor of the unit according to the invention, the unit having a thickness of about 30 cm.

According to Figures 4 and 5 it appears from the values measured that the method according to the invention gives units having very good values relating to the sound absorption and the reduction factor, making the units very suitable to be used as noise protecting screens, especially outdoors.

It is obvious for the man skilled in the art that the units according to the invention can be designed in different sizes, thicknesses, with different designs and profiles, and in different colours according to one's wishes.