Elastomer Composition for an Insert for Supporting a Wheel Tyre, Insert Comprising the Composition and Mounted Assembly Incorporating the Insert

Abstract

The invention concerns an elastomer composition for a self-supporting insert (1) intended to support a tyre of a wheel of a vehicle, an insert of which at least one layer (3) comprises said composition and a mounted assembly incorporating said insert. The invention applies to a non-pneumatic mounted assembly, in particular for a vehicle with two wheels, in which each of the tyres is permanently supported by said insert, The elastomer composition comprises, principally by mass, a mixture of at least one first thermoplastic elastomer and at least one second thermoplastic elastomer, and said composition is such that said at least one first thermoplastic elastomer is a copolyamide (COPA) and said at least one second thermoplastic elastomer is a thermoplastic styrene (TPS) elastomer.

Claims

1. An elastomeric composition for a self-supporting support insert for a non-pneumatic tire of a vehicle wheel, the composition comprising predominantly by weight a blend of at least one first thermoplastic elastomer and of at least one second thermoplastic elastomer, wherein said at least one first thermoplastic elastomer is a copolyamide (COPA) and said at least one second thermoplastic elastomer is a styrenic thermoplastic elastomer (TPS).

2. The elastomer composition as claimed in claim 1, wherein said blend comprises said at least one first thermoplastic elastomer in a weight fraction of less than or equal to that of said at least one second thermoplastic elastomer in said blend.

3. The elastomer composition as claimed in claim 2, wherein the composition is free of thermoplastic polyurethane (TPU), the weight fractions in said blend of said at least one first thermoplastic elastomer and of said at least one second thermoplastic elastomer being respectively between 5% and 49% and between 95% and 51%.

4. The elastomer composition as claimed in claim 1, wherein said at least one second thermoplastic elastomer comprises one said TPS of linear block type and one said TPS of block type grafted by a compatibilizing agent.

5. The elastomer composition as claimed in claim 4, wherein said linear TPS and said grafted TPS are respectively present in said at least one second thermoplastic elastomer in weight fractions of between 40% and 60% and 60% and 40%, and are each selected independently from the group consisting of styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-butylene-ethylene-styrene (SEBS) and styrene-ethylene-propylene-styrene (SEPS) block copolymers.

6. The elastomer composition as claimed in claim 5, wherein said linear TPS is an SEBS and said grafted TPS is an SEBS grafted by maleic anhydride constituting said compatibilizing agent.

7. The elastomer composition as claimed in claim 1, wherein the composition comprises: in a weight fraction of between 3% and 40%, said at least one first thermoplastic elastomer that comprises at least one polyether-block-amide (PEBA), in a weight fraction of between 65% and 40%, said at least one second thermoplastic elastomer that preferably comprises one said TPS of linear type and one said TPS of the type grafted by a compatibilizing agent, and in a weight fraction of between 20% and 32%, a plasticizer, preferably a paraffinic plasticizer.

8. The elastomer composition as claimed in claim 1, wherein the composition has a rebound resilience, measured according to the ISO 4662:2009 standard, which is greater than or equal to 70%, for example equal to 75%.

9. The elastomer composition as claimed in claim 1, wherein the composition is compact, being free of blowing agent.

10. The elastomer composition as claimed in claim 1, wherein the composition is cellular with closed cells, comprising a blowing agent in a weight fraction of between 1% and 20% preferably in the form of thermoplastic microspheres containing a blowing gas forming said blowing agent.

11. A self-supporting support insert for a non-pneumatic tire of a vehicle wheel, the insert having a circumferential length and a radial thickness rendering it suitable to be fitted between said wheel and said tire while permanently supporting the latter, the insert comprising, over said length, at least one first layer having a radial thickness of greater than 2 mm, wherein said at least one first layer consists of a elastomer composition as claimed in claim 1.

12. The self-supporting support insert as claimed in claim 11, wherein the insert has a substantially circular cross section delimited radially on the outside by a second outer layer having a radial thickness of between 100 m and 1 mm and consisting of a crosslinked elastomeric composition.

13. The self-supporting support insert as claimed in claim 12, wherein said crosslinked elastomeric composition comprises predominantly by weight at least one third thermoplastic elastomer selected from thermoplastic vulcanizates (TPVs), crosslinked copolyesters (COPEs) and blends thereof, said crosslinked elastomeric composition preferably comprising in addition a thermosetting resin such as an epoxy resin dispersed in said at least one third thermoplastic elastomer, especially in the case where the latter comprises one or more COPEs.

14. The self-supporting support insert as claimed in claim 12, wherein the insert is hollow over said length and has a tubular geometry comprising one said first layer which is preferably compact, and said second outer layer.

15. The self-supporting support insert as claimed in claim 12, wherein the insert is solid over said length and has a cellular core with closed cells, one said first intermediate layer which is preferably compact surrounding said core, and said second outer layer.

16. A non-pneumatic fitted assembly for a wheeled vehicle selected from bicycles, motorcycles, handling vehicles, wheelchairs and rollators, the fitted assembly comprising a wheel, a non-pneumatic tire fitted on the wheel that comprises a tread and two beads fitted against two edges of the wheel, and a self-supporting support insert for the tire that is fitted between the wheel and the tire while permanently supporting the latter, wherein said self-supporting support insert is as defined in claim 11.

Description

[0044] Other features, advantages and details of the present invention will emerge on reading the following description of several exemplary embodiments of the invention given by way of illustration and non-limitingly, the description being given with reference to the appended drawings, among which:

[0045] FIG. 1 is a cross-sectional view of a tubular insert according to said first embodiment of the invention,

[0046] FIG. 2 is a cross-sectional view of a solid insert according to said second embodiment of the invention, and

[0047] FIG. 3 is a cross-sectional view of a tubular insert according to said first embodiment, in accordance with a variant of FIG. 1.

[0048] The inserts 1, 10, and 10 from FIGS. 1, 2 and 3 are intended to be positioned between a wheel rim and a non-pneumatic tire (which are not illustrated) so as to form a fitted assembly without inflation gas for example for a two-wheeled vehicle such as a bicycle, it being specified that these inserts 1, 10, and 10 may be used with different shapes and/or dimensions in order to equip non-pneumatic fitted assemblies of other vehicles such as those mentioned above, in a nonlimiting manner.

[0049] The tubular insert 1 from FIG. 1 is thus intended to delimit a non-inflated internal space 2, and it is formed: [0050] of a compact inner layer 3 which has an annular cross section and which consists of a compact thermoplastic elastomer composition according to the invention, i.e. the elastomer matrix of which is based on a blend comprising at least one COPA and at least one TPS, and [0051] of a compact outer layer 4 or skin covering the inner layer 3 over the whole of its circumference and its length and which consists of a crosslinked thermoplastic elastomer composition according to the invention, i.e. the elastomer matrix of which is based on at least one TPV and/or on at least one crosslinked COPE.

[0052] In the example from FIG. 1 showing an insert 1 at rest for a bicycle wheel (enlargement of around 3), the inner layer 3 has a thickness of 7.5 mm and the outer layer 4 a thickness e.sub.1 of 0.5 mm (hence a thickness e of 8 mm for the layers 3 and 4), with internal and external diameters of the insert 1 respectively of 17.5 mm and 33.5 mm.

[0053] The solid insert 10 of rod type from FIG. 2 is formed: [0054] of an expanded core 11 of cellular type with closed cells which constitutes the major part, by volume, of the insert 10 and which consists for example of a cellular thermoplastic elastomer composition according to the invention, i.e. based on at least one COPA and on at least one TPS, [0055] of a compact intermediate layer 12 which covers the expanded core 11 over the whole of its circumference and its length and which consists of a compact thermoplastic elastomer composition according to the invention based on at least one COPA and on at least one TPS, and [0056] a compact outer layer 13 similar to that from FIG. 1 which consists of a crosslinked thermoplastic elastomer composition based on at least one TPV and/or on at least one crosslinked COPE.

[0057] In the example from FIG. 2 that illustrates an insert 10 at rest for a bicycle wheel (enlargement of around 3), the intermediate layer 12 has a thickness of 2.5 mm and the outer layer 13 a thickness e.sub.1 of 0.5 mm (hence a thickness e of 3 mm for the layers 12 and 13), with an external diameter of the insert 10 of 33.5 mm.

[0058] The tubular insert 10 from FIG. 3 is formed: [0059] of a compact inner layer 3 or skin which externally delimits a non-inflated internal space 2 while having an annular cross section and which consists of a crosslinked thermoplastic elastomer composition based on at least one TPV and/or on at least one crosslinked COPE, [0060] of an expanded tubular core 11 of cellular type with closed cells which constitutes the major part, by volume, of the insert 10 and which consists for example of a cellular thermoplastic elastomer composition according to the invention, i.e. based on at least one COPA and on at least one TPS, [0061] of a compact intermediate layer 12 which covers the expanded core 11 over the whole of its circumference and its length and of a compact thermoplastic elastomer composition according to the invention based on at least one COPA and on at least one TPS, and [0062] a compact outer layer 13 or skin similar to the inner layer 3 which consists which consists of a crosslinked thermoplastic elastomer composition based on at least one TPV and/or on at least one crosslinked COPE.

[0063] In the example from FIG. 3 showing an insert 10 at rest for a bicycle wheel, the inner layer 3 and outer layer 13 each have a same thickness e.sub.1 of 0.50 mm (with a total thickness e of 3 mm for the layers 12 and 13 as for the insert 10 from FIG. 2), the insert 10 having an external diameter of 33.5 mm.

[0064] Each of the elastomeric compositions forming the layers 3, 4, 11, 12, 13 and 3, 11, 12, 13 were obtained essentially in two steps: [0065] a first step of thermomechanical working of each composition, optionally with addition of a blowing agent, preferably in the form of thermoplastic microspheres containing a blowing gas, and [0066] a second step of shaping by extrusion (processing in a standard extrusion line comprising extrusion, cooling and cutting stations) or by co-injection molding in a mold.

[0067] The extruded or co-injection molded self-supporting insert 1, 10, 10 was finally inserted inside the non-pneumatic tire fitted to the wheel.

[0068] Examples of compositions that can be used for inserts according to invention:

1) Inner Layer or Intermediate Layer Compositions:

[0069] Two compact thermoplastic elastomer compositions I1 and I2 that can be used for the inner layer 3 of the insert 1, the intermediate layer 12 of the insert 10 and the intermediate layer 12 of the insert 10 were prepared as indicated above, which were both based on a COPA of PEBA type and on a blend of two TPSs of SEBS type (the formulations below are expressed in parts by weight), and the rebound resiliences obtained for I1 and I2 were measured according to the ISO 4662:2009 standard.

TABLE-US-00001 Composition I1: Pebax 4033 PEBA 10 parts Kraton G1651 SEBS 50 parts Kraton FG1901 MAH-grafted SEBS 50 parts Torilis 7200 paraffinic plasticizer 50 parts Resilience obtained 75%.

[0070] It will be noted that the resilience obtained for this composition I1 comprising TPSs and a COPA in respective weight fractions of 63% and 6% is very high, which advantageously makes it possible to give an insert 1, 10, 10 according to the invention incorporating it a dynamic behavior that is progressive starting from moving off and adapted to the stresses when rolling.

TABLE-US-00002 Composition I2: Pebax 4033 PEBA 75 parts Kraton G1651 SEBS 50 parts Kraton FG1901 MAH-grafted SEBS 50 parts Torilis 7200 plasticizer 50 parts Resilience obtained 70%.

[0071] It will be noted that the high resilience obtained for this composition I2 comprising TPSs and a COPA in respective weight fractions of 44% and 33% also makes it possible to give an insert 1, 10, 10 according to the invention incorporating it this progressive resilient dynamic behavior that is adapted to the stresses when rolling.

2) Outer Layer Compositions:

[0072] Two crosslinked thermoplastic elastomer compositions I3 and I4 that can be used for the outer layers 4 and 13 of the inserts 1 and 10 and for the inner layer 3 and outer layer 13 of the insert 10 were prepared as indicated above, which were respectively based on a TPV of EPDM-PP type (of Vegaprene) for the composition I3 and based on a blend of two COPEs reinforced by a thermosetting resin for the composition I4 (the formulations below are also expressed in parts by weight).

TABLE-US-00003 Composition I3: EPDM: VISTALON 3666 91.4 parts Polypropylene: Finapro PPH 3060 170 parts Activator: stearic acid 0.5 part Activator: active ZnO 3 parts Processing aid: PEG 4000 5 parts Processing aid: Polyplastol 1 part Processing aid: Crodamide E 1 part Phenolic resin: SP 1055 resin 6 parts Carbon black: FEF 550 22 parts Plasticizer: Torilis 7200 24.8 parts

TABLE-US-00004 Composition I4: COPE: Arnitel PM460 100 parts Epoxy resin: DER330 5 parts Crosslinking agent: Jeffamine T403 2 parts

[0073] The running tests carried out by the applicant on the basis of these compositions showed that these compositions I3, I4 of inner layers 4, 13, 3, 13 according to the invention contribute significantly to making the insert 1, 10, 10 self-supporting when rolling.

[0074] Generally, it will be noted that these formulations I1, I2 of inner or intermediate layers and I3, I4 of outer layers of inserts according to the invention are given by way of example and non-limitingly, and that it is in particular possible to use COPAs other than the PEBAs tested for these inner and intermediate layers, and/or TPVs or COPEs other than those tested for these outer layers.