RESILIENT SOLE AND METHOD FOR MANUFACTURING SAME
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.
The present invention relates to a resilient sole arranged to be attached to a concrete layer or which is positioned between a concrete layer and a ballast, as well as a method for manufacturing such a resilient sole.
The present invention also relates to an assembly comprising a concrete layer and a resilient sole such as mentioned above.
Such soles are well known from the state of the art.
In the construction field, such soles are arranged to be attached to concrete layers or blocks.
In the railway field, such soles are positioned between the rails and the ballast, the ballast forming the bed of the railway line.
The rail is a treated wood, steel or concrete transverse part, on which the rails of a railway line are attached, in order to keep them parallel and to transmit the load that they support to the ballast.
The ballast is formed of crushed stones and is arranged to receive the rails on which the railway rails rest.
These types of soles positioned between the ballast and the rails aim to dampen the propagation of vibrations generated by the passage of the train on the rails to the bed of the underlying railway line and therefore to the ballast, to avoid wear, as well as the compression of the ballast, as well as to avoid wear of the rails and in particular, of the concrete rails by the ballast. Indeed, without soles positioned between the ballast and the rails, the concrete rails would therefore be in direct contact with the crushed stones of the ballast. This would therefore lead to cracks and a concrete becoming brittle over time.
For example, document FR2935399 describes a resilient sole which is equipped with wires forming stainless steel loops which are buried in an extruded viscoelastic plate with a maximum of 4 loops per cm2 of extruded viscoelastic plate during moulding. These wires are also buried in the concrete block during the moulding of the latter.
Unfortunately, these wires are easily detached from the viscoelastic plate, wherein they are directly buried, easily deformed or broken due to the shearing stresses under the effect of the repeated passages of the trains on the rails of the railway.
In addition, the wires do not make it possible to obtain a satisfactory fastening of the concrete to the extruded viscoelastic plate.
Document WO2019201761 describes a sole comprising a resilient layer and a fibre layer which comprises different elements such as grooves, randomly arranged fibres and solidified zones. The solidified zones are obtained by heat treatment or local bonding of fibres.
Unfortunately, the manufacture of this sole requires considerable time. The fibrous layer must be reinforced in certain places, the fibres must not be present or barely present in other places of the upper surface of the resilient layer and reinforcements of certain places must be done by adding more numerous fibres.
Document WO2012040798 describes a resilient sole comprising a rubber-based resilient layer and a groundsheet arranged on the resilient layer. The groundsheet comprises, on the one hand, a sheet base in the form of an extruded film and, on the other hand, filaments which can be in the form of loops, mushrooms or hooks. The filaments are made of polymers and are attached to the extruded film by welding. The resilient layer and the extruded film are associated with one another by bonding or welding of the base of the groundsheet to the resilient layer.
Unfortunately, first this resilient sole is associated with a specific concrete, the manufacture of which is explained in the document. The filaments are affixed against the concrete milk during the hardening of the rails in order to not impact the resistance of the rails. This sole is therefore highly dependent on the quality of the concrete used to form the rail. In addition, this document mentions nothing regarding the resistance of the concrete rails, fibres and resilient layer assembly. However, it is probable that later, the bonding or the welding of the resilient layer to the base of the sheet (extruded film) is a source of fragility of the “concrete rails, fibres and resilient layer” assembly.
Document EP129852 describes a resilient sole comprising an extruded resilient layer and a plastic fibrous layer entangled in the extruded resilient layer by welding, the fibrous layer being composed of a non-woven geotextile.
Unfortunately, the use of a geotextile-type textile involves a significant cost for producing these types of resilient soles which are present under each rail of the railway line.
It is also probable that later, as for document WO2012040988, the welding of the resilient layer to the base of the geotextile or of a plastic non-woven fabric is a source of fragility of the “concrete rails, fibres and resilient layer” assembly.
In patent application WO2009/108972, a resilient sole to be attached, for example, to concrete rails is disclosed. This sole comprises several elastomer material layers which are reinforced by a reinforcing layer arranged between two elastomer layers, and which are covered with a bonding layer intended for a fastening with the concrete. During the manufacture of the sole, these reinforcing or bonding layers are, one totally, the other partially, buried in the elastomer layers during the expansion reaction of these. Such soles are complex to manufacture and assuringly do not enable a manufacture from vulcanised rubber waste which is recycled.
The invention aims to overcome the disadvantages of the state of the art by providing a robust resilient sole arranged to confer a “sole-under-sole rail” assembly to resist the stresses exerted by the railway line, from vulcanised rubber waste, and using a simple and economic manufacturing method.
To resolve this problem, a resilient sole arranged to be attached to a concrete layer or positioned between a concrete layer and a ballast is provided according to the invention, which is formed of a recycled rubber layer, in the revulcanised state after devulcanisation, and a layer of structured fibres, which is arranged so as to be in contact with the rubber layer, said fibres being partially impregnated in said rubber layer and having a free thickness of structured fibres.
As can be observed, in the sole according to the present invention, the rubber layer of the resilient sole comes from a recycling process and can comprise production waste, cutting waste or also used waste.
By the term “structured fibres”, this means, according to the invention, fibres entangled in a weft, or fibres arranged on several layers of superposed textile fibres. These fibres can be mixed during the manufacturing process using special hook needles to form a dense and compact layer of structured fibres which is optionally then coated, in order to solidify the assembly, like for example felts or carpets needled, used frequently for pop-up events (exhibition stand, red carpet, etc.).
The structured fibres can come from the recycling process. According to the type of structured fibres, like for example in the case of production waste, it is possible according to the present invention to use directly structured fibres to form said layer of structured fibres of the resilient sole.
The rubber used in the resilient sole according to the present invention is a recycled rubber, more specifically a rubber which has been devulcanised. The devulcanised rubber is a rubber which has been decrosslinkable, i.e. a rubber wherein some of the sulphur bonds have been broken.
The rubber is then revulcanised by a hot pressing method. The rubber obtained is therefore a rubber wherein the sulphur bonds are recreated during the hot pressing.
According to the present invention, the structured fibres of the layer of structured fibres are partially impregnated in the rubber layer. This impregnation occurs during the hot pressing of the formed layer of the devulcanised rubber. During hot pressing, the rubber is revulcanised in the thickness of the rubber layer, but also around structured fibres.
According to the present invention, by the term “partially impregnated in the rubber layer”, it is understood that the layer of structured fibres has a free thickness of structured fibres, i.e. non-impregnated by the revulcanised rubber and a thickness of structured fibres impregnated in the revulcanised rubber.
Surprisingly, the association of at least one recycled rubber layer and at least one layer of structured fibres impregnated in the revulcanised rubber makes it possible to obtain a robust resilient sole and resistant to the tearing of the layer of structured fibres which are impregnated in the revulcanised rubber layer according to the tests in force.
The tests in forced are: standard ISO 37 to measure the resistance to traction, as well as the Shore hardness, standard EN16730 to measure the static and dynamic rigidity, the resistance to ageing, the resistance to fatigue and the resistance to tearing.
In addition, when the under-rail sole is associated with a concrete rail during the manufacture of it, the thickness of structured fibres non-impregnated in the revulcanised rubber layer is thus impregnated in the concrete before hardening. Once the concrete has hardened, it has been identified also most surprisingly that the assembly has an excellent resistance to the tearing of the layer of structured fibres of the concrete. The layer of impregnated structured fibres is and thus remains integral on the one hand with the rubber, and on the other hand, with the concrete during the tearing tests, which forms a resilient sole resistant to the exerted stresses, like for example those exerted by the railway line and its use. Advantageously, the resistance to tearing of the resilient sole according to the invention/rail exceeds 0.8 MPa.
Advantageously, the density of the structured fibres of the resilient sole according to the present invention is between 150 g/m2 and 800 g/m2, preferably between 170 and 750 g/m2, advantageously between 190 and 500 g/m2. Such a density of structured fibres offers the advantage of increasing the resistance to tearing during tests.
Advantageously, the fibres of the resilient sole according to the present invention are impregnated at a depth of between 0.5 and 2 mm, preferably between 0.7 and 1.5 mm, preferably between 0.9 and 1 mm in said revulcanised rubber layer. This has the advantage of creating a revulcanised rubber interphase—robust fibres, and resistant to the stresses exerted by the railway line. The resistance to fibre/rubber tearing advantageously exceeds 1 MPa. This interphase enables the sole to have a resistance to tearing of the concrete block when it is present, as well as a resistance to tearing of the rubber layer.
Preferably, said devulcanised-revulcanised recycled rubber layer of the resilient sole according to the present invention has a Shore hardness of between 50 and 90 Shore A, according to the standard measuring model, the durometer. This has the advantage of obtaining a wide range of rigidity of the rubber, and therefore to cover the needs of the different actors of the targeted market.
Preferably, said devulcanised-revulcanised recycled rubber layer of the resilient sole according to the present invention has a resistance to traction greater than or equal to 7 MPa, preferably greater than or equal to 8 MPa, advantageously greater than or equal to 9 MPa, even more advantageously equal to 10 MPa. This has the advantage that the recycled rubber layer composing the resilient sole resists wear, like for example wear that the ballast causes following contact between the lower surface of the recycled rubber layer and the ballast.
Preferably, said devulcanised-revulcanised recycled rubber layer of the resilient sole according to the present invention has an extension to rupture greater than 150%, preferably greater than 200%, even greater than 250%. This has the advantage that the recycled rubber layer composing the resilient sole is resistant to the different forces undergone by the sole and sufficiently rigid to ensure its role of dissipator of vibrations that the railway line undergoes.
Preferably, said fibres of the layer of structured fibres of the resilient sole according to the present invention are chosen from the group of natural or synthetic materials, like for example polyester, polypropylene, polystyrene, polyethylene, wool, cotton, hemp, coconut fibres.
Advantageously, said rubber layer of the resilient sole according to the present invention comprises rubber chosen from the group of natural or synthetic materials, like for example natural polyisoprene, isoprene polymer, polybutadiene, styrene-butadiene copolymer.
Other embodiments of the resilient sole according to the invention are indicated in the accompanying claims.
The present invention also relates to an assembly comprising a concrete layer and a resilient sole such as described above, wherein said structured fibres are further partially impregnated in said concrete layer, on the free thickness of structured fibres.
Advantageously, the concrete layer can be a concrete block or a moulded concrete element, advantageously a railway rail.
In an embodiment of the assembly according to the present invention, said fibres are impregnated in the concrete layer of the assembly according to the present invention on a thickness of between 0.3 and 2 mm, preferably between 0.4 and 1.8 mm, more specifically, between 0.5 and 1 mm. Advantageously, an impregnation of the fibres on such a thickness makes it possible to obtain a resilient sole-integral concrete layer assembly.
Other embodiments of the “concrete layer-resilient sole” assembly according to the invention are indicated in the accompanying claims.
The invention also aims to provide a production method which enables a production in an industrial quantity and at a low cost of a quality, robust resilient sole, and resistant to the stresses exerted, for example, by the regular passage of trains.
According to the invention, this problem is resolved by a method for manufacturing a resilient sole comprising:
-
- a devulcanisation of recycled rubber, with formation of a devulcanised recycled rubber mass,
- an addition of at least one devulcanised recycled rubber additive,
- a superposition of a layer of structured fibres and of the devulcanised recycled rubber with the obtaining of two superposed layers, and
- a hot pressing of 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.
The method for manufacturing a resilient sole according to the present invention has the advantage of producing, from rubber waste, a resilient sole simply and rapidly, at a low cost, by making it possible to meet the requirements of each actor of the market. The sole is made from two layers, without any bonding between them.
Devulcanised rubber, which is a recycled rubber, is obtained by devulcanisation. This devulcanisation can be done at the start of manufacturing the resilient sole or it can be done upstream of manufacturing said resilient sole.
More specifically, this devulcanised rubber is a devulcanised rubber, reactivated by adding at least one additive.
The layer of structured fibres is, by superposition, brought into contact with said devulcanised rubber layer, before pressing. This step makes it possible to obtain two superposed layers.
The two superposed layers are brought to a press and the hot-pressed at a temperature of between 100 and 180° C., preferably between 140 and 170° C., preferably between 150 and 160° C. during a predetermined time interval. This hot pressing will thus enable the revulcanisation of the devulcanised rubber layer and, during this revulcanisation, an at least partial impregnation of the structured fibres of the layer of structured fibres in the rubber layer thus forming a revulcanised rubber-fibre interphase. Thus, during hot pressing, the rubber is revulcanised in the thickness of the rubber layer, but also around structured fibres. The structured fibres have a melting point greater than the hot pressing temperature.
According to the present invention, the pressing is the result of the force necessary to compress the rubber. The hot pressing can be carried out by any device known for this purpose, in particular in a mould or also between two pressing strips. The pressing strips are adjusted to a layer thickness between 10 and 25% less than the thickness of the two superposed layers.
According to the present invention, by the term “revulcanised rubber”, this means that the rubber is a rubber wherein sulphur bonds are recreated during hot pressing.
By the term “reactivated devulcanised rubber”, this means according to the present invention, a rubber of which the reactivation of sulphur bonds is ready to be triggered.
According to the present invention, by the term “partial impregnation of structured fibres”, this means that the layer of structured fibres has, at the end of the method, a free thickness of structured fibres, i.e. non-impregnated in the revulcanised rubber and a thickness of structured fibres impregnated in the revulcanised rubber.
The method for manufacturing a resilient sole according to the present invention has the advantage or providing a resistant, robust and quality sole.
During devulcanisation, it is advantageous that the viscosity of the devulcanised rubber is less than 70 MU, preferably less than 50 MU, more specifically less than 40 MU, measured on a Mooney viscometer. This viscosity will favour the formation of a revulcanised rubber-fibre interphase by the at least partial impregnation of the fibres of the fibrous structure in the rubber layer obtained during hot pressing. It is preferable, but not excluded, that there is no total impregnation of the fibres during the compression step.
In addition, this viscosity will make it possible to produce varied resilient soles which will be able to meet the expectations of each of the actors of the targeted market. Indeed, the manufacturing method makes it possible to obtain resilient soles in a wide range of sole rigidities.
In addition, the method for manufacturing a resilient sole according to the present invention has the advantage of being achieved at a low cost by using a rubber coming from the recycling process and a layer of structured fibres, the basic features of which make it possible to obtain it at a low cost. It therefore enables a circular economy by using company waste to give them a new life in another technical field.
The dependent claims refer to other advantageous embodiments.
In a preferred embodiment, the additive(s) used in the addition step comprise sulphur and/or at least one resin and/or at least one reaction activator or accelerator and/or carbon black.
Advantageously, said at least one resin according to the present invention is a thermoplastic resin chosen from the group comprising resins having at least one phenol group, at least one aromatic group, at least one styrene group, or any other resin which could be used with sulphur-vulcanised rubber or their combination.
Preferably, said at least one reaction activator or accelerator according to the present invention is chosen from the group comprising CBS, stearic acid, zinc oxide.
Advantageously, said predetermined time interval of the hot pressing step of the method for manufacturing the sole according to the present invention is between 3 and 12 minutes, preferably between 4 and 10 minutes, more specifically, between 5 and 6 minutes.
According to an advantageous embodiment of the invention, after the addition of at least one abovesaid additive, the devulcanised recycled rubber mass is shaped and the layer of structured fibres and the devulcanised recycled rubber, shaped, are superposed so as to form said two layers.
It can occur, in certain cases, a total impregnation of the fibres in the rubber layer during revulcanisation, during hot pressing. In this case, the method further comprises a brushing on the surface of the impregnated structured fibres, so as to make these partially free, on a predetermined thickness.
Other embodiments of the method for manufacturing a resilient sole according to the invention are indicated in the accompanying claims.
Other features, details and advantages of the invention will emerge from the description given below, in a non-limiting manner, and by making reference to the drawings and to the examples.
In the figures, the identical or similar elements have the same references.
-
- a revulcanised rubber layer 4,
- a layer of structured fibres 5 partially impregnated in the revulcanised rubber layer 4,
- an interphase 6 comprising impregnated structured fibres 7 and revulcanised rubber 4.
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.
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.
Then, a layer of structured fibres 5 is superposed on the devulcanised rubber layer and two superposed layers are obtained.
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.
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.
In
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.
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.
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.
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
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.
Thus, the mould can be opened, the non-compressed excess material removed, and the resilient sole illustrated in
-
- a revulcanised rubber layer 9,
- a layer of structured fibres 13 partially impregnated in the revulcanised rubber layer 9, and
- an impregnated felt fibre-revulcanised rubber interphase 16.
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
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.
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/m2 and 800 g/m2.
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.
Type: Application
Filed: Sep 29, 2021
Publication Date: Sep 28, 2023
Inventors: Olivier PRUD'HOMME (Wavre), Said SEGHAR (Valenciennes)
Application Number: 18/246,770
