RESILIENT SOLE AND METHOD FOR MANUFACTURING SAME

Abstract

Resilient sole 1 which is attached to a concrete layer (2) or which is positioned between a concrete layer (2) and ballast (3), and which is formed by a layer (4) of recycled rubber, in the revulcanised state after devulcanisation, and a layer (5) of structured fibres which is arranged so as to be in contact with the rubber layer, the fibres being partially impregnated in the rubber layer and having a free thickness (8) of structured fibres, assembly comprising the sole and method for manufacturing same.

Claims

1. A resilient sole, arranged in particular to be attached to a concrete layer or positioned between a concrete layer and a ballast, comprising: a recycled rubber layer, in the revulcanised state after devulcanisation, and a layer of structured fibres, arranged in contact with the rubber layer, said fibres being partially impregnated in said rubber layer and having a free thickness of structured fibres.

2. The resilient sole according to claim 1, wherein the structured fibres have a density of between 150 g/m.sup.2 and 800 g/m.sup.2.

3. The resilient sole according to claim 1, wherein the fibres are impregnated at a depth of between 0.5 and 2 mm, in the revulcanised state.

4. The resilient sole according to claim 1, wherein said recycled rubber layer in the revulcanised state has a Shore hardness of between 50 and 90, according to the standard measuring model, the durometer.

5. The resilient sole according to claim 1, wherein said fibres are chosen from the group of natural or synthetic materials, like polyester, polypropylene, polystyrene, polyethylene, wool, cotton, hemp, coconut fibres.

6. The resilient sole according to claim 1, wherein said recycled rubber layer comprises the rubber chosen from the group of natural or synthetic materials, like natural polyisoprene, isoprene polymer, polybutadiene, styrene-butadiene copolymer.

7. The resilient sole according to claim 1, wherein said rubber layer has a resistance to traction greater than or equal to 7 MPa.

8. The resilient sole according to claim 1, wherein said rubber layer has an extension to rupture greater than 150%.

9. An assembly, comprising: a concrete layer; and a resilient sole, comprising a recycled rubber layer, in the revulcanised state after devulcanisation, and a layer of structured fibres, arranged in contact with the rubber layer, said fibres being partially impregnated in said rubber layer and having a free thickness of structured fibres, wherein said structured fibres are further partially impregnated on the free thickness of structured fibres in said concrete layer.

10. The assembly according to claim 9, wherein said fibres are impregnated in the concrete block on a thickness of between 0.3 and 2 mm.

11. A method for manufacturing a resilient sole comprising: devulcanising recycled rubber, including formation of a devulcanised recycled rubber mass, adding at least one devulcanised recycled rubber additive, superpositioning a layer of structured fibres and devulcanised recycled rubber, including obtaining of two superposed layers, hot pressing said two superposed layers at a temperature of between 100 and 180° C. during a predetermined time interval with revulcanisation of the devulcanised recycled rubber and formation of a resilient sole where the structured fibres are at least partially impregnated in said rubber layer during revulcanisation, by forming a revulcanised rubber-fibre interphase.

12. The method for manufacturing a resilient sole according to claim 11, wherein said at least one additive comprises sulphur, or at least one resin, or at least one reaction activator or accelerator, or carbon black.

13. The method for manufacturing a resilient sole according to claim 12, wherein said at least one resin is a resin chosen from the group comprising resins having at least one phenol group, at least one aromatic group, at least one styrene group, and any other resin which could be used with sulphur-vulcanised rubber and their combination.

14. The method for manufacturing a resilient sole according to claim 12, wherein said at least one reaction activator is chosen from the group comprising CBS, stearic acid and zinc oxide.

15. The method for manufacturing a resilient sole according to claim 11, wherein after the addition of at least one abovesaid additive, the devulcanised recycled rubber mass is shaped and in that the layer of structured fibres and the devulcanised, shaped recycled rubber, are superposed so as to form said two layers.

16. The method for manufacturing a resilient sole according to claim 11, wherein during the hot pressing, the structured fibres are totally impregnated in said rubber layer during revulcanisation, the method further comprising superficially brushing the impregnated structured fibres, so as to make these partially free, on a predetermined thickness.

17. The method for manufacturing a resilient sole according to claim 11, wherein the superposition and hot pressing steps are carried out in a mould.

18. The method for manufacturing a resilient sole according to claim 11, wherein said devulcanised recycled rubber has a viscosity less than 70 MU, measured on a Mooney viscometer.

Description

[0072] FIG. 1 is a cross-sectional view of a resilient sole according to the present invention.

[0073] FIG. 2 is a cross-sectional view of an assembly comprising a concrete layer arranged to be used as a rail and a resilient sole according to the present invention.

[0074] FIGS. 3 to 6 illustrate a method for manufacturing a resilient sole according to the invention.

[0075] FIG. 7 illustrates a superficial brushing step after hot pressing, according to a particular embodiment of the manufacturing method according to the invention.

[0076] In the figures, the identical or similar elements have the same references.

[0077] FIG. 1 illustrates a resilient sole 1 according to the invention arranged to be positioned between a concrete block (not represented) and a ballast (not represented). This resilient sole 1 comprises: [0078] a revulcanised rubber layer 4, [0079] a layer of structured fibres 5 partially impregnated in the revulcanised rubber layer 4, [0080] an interphase 6 comprising impregnated structured fibres 7 and revulcanised rubber 4.

[0081] According to the present invention, by the term “partially impregnated in the revulcanised rubber layer 4”, this means that the layer of structured fibres 5 has a free thickness 8 of structured fibres, i.e. not impregnated in the revulcanised rubber layer, and a thickness 7 of impregnated structured fibres in the revulcanised rubber 4.

[0082] To obtain this resilient sole 1, a devulcanised rubber sample is taken, coming from tyre waste of different vehicles. After having added at least one additive intended to reactive the devulcanised rubber to this sample, it has been shaped in the form of a strip. Said devulcanised rubber strip is positioned on a lower conveyor belt.

[0083] Then, a layer of structured fibres 5 is superposed on the devulcanised rubber layer and two superposed layers are obtained.

[0084] Said two superposed layers a conveyed to a press. Said two superposed layers are pressed at a temperature of 120° C. for 5 minutes. The rubber has thus been revulcanised during pressing and a resilient sole 1 is obtained according to the present invention. During hot pressing, the structured fibres have been partially impregnated in said revulcanised rubber layer 4 by forming the revulcanised rubber-fibre interphase 6.

[0085] FIG. 2 illustrates an assembly 10 comprising a concrete layer 2 arranged to be used as a rail and a resilient sole 1 according to the present invention, assembly wherein said structured fibres 5 are further partially impregnated, on the free thickness 8 of structured fibres, in said concrete layer 2, and this before taking the concrete.

[0086] The rail, formed from the concrete layer 2 and equipped with a resilient sole 1 according to the invention, for the dissipation of vibrations, can thus be placed on a ballast 3.

[0087] In FIGS. 3 to 6, a resilient sole according to the invention is manufactured according to another embodiment of the invention.

[0088] After devulcanisation, the recycled, devulcanised rubber mass, is mixed with additives which promote the mainly mechanical features of the sole. In particular, carbon black which modifies the hardness, the stiffness and the dissipative power of the vibrations of the obtained sole can be added. The activators/accelerators enable an activation or acceleration of the reactivity of the rubber and therefore of its revulcanisation, which will also determine the cross-linking density of the sole.

[0089] The devulcanised mass is, after adding the abovementioned additives, shaped, in particular in the form of a plate 11 having the dimensions of a mould 12. Likewise, a thermoplastic, preferably polypropylene felt layer 13, is cut to the size of the mould.

[0090] The mould 12 is preheated to a temperature less than the melting point of the fibres of the felt, preferably between 140 and 170° C., advantageously between 150 and 160° C.

[0091] In the preheated mould, first the cut felt 13 is introduced, then the devulcanised, shaped rubber plate 11 is superposed there. Advantageously, the height of the felt assembly 13 and rubber plate 11 is greater than the depth of the cavity of the mould 12. Then, the cover 14 of the mould 12 is closed, as represented in FIG. 4, and the assembly is hot compressed at a pressure preferably greater than 2 MPa, advantageously 6 MPa. This pressure must be sufficient to discharge the excess material 15 outside of the mould, as represented in FIG. 5.

[0092] The vulcanisation time depends on the activation/acceleration of the devulcanised rubber mass used. This time can vary between 2 and 15 minutes, advantageously between 3 and 7 minutes.

[0093] Thus, the mould can be opened, the non-compressed excess material removed, and the resilient sole illustrated in FIG. 6 extracted from the mould, which has [0094] a revulcanised rubber layer 9, [0095] a layer of structured fibres 13 partially impregnated in the revulcanised rubber layer 9, and [0096] an impregnated felt fibre-revulcanised rubber interphase 16.

[0097] In certain cases, in particular when the devulcanised rubber is of low viscosity and/or the felt of low density, the fibres of the felt are totally buried in the rubber layer after the hot pressing step, by forming a layer of totally impregnated fibres 20 in the revulcanised rubber layer 9. A superficial brushing of the layer of impregnated fibres 20 is thus necessary to release some of the fibres on a predetermined thickness. This brushing can be done as represented in FIG. 7, using a circular brush 17 mounted on an axis and adjusted to a predetermined height of a conveyor belt 18. The passage under this brush of the resilient sole exiting from the mould will thus clear a free thickness 19 of structured fibres, which may enable the subsequent fastening of a concrete layer.

[0098] It is well understood that the present invention is not, in any way, limited to the embodiments described above and that plenty of modifications can be applied to it, without moving away from the scope of the accompanying claims.