Interior trim part for motor vehicle

Abstract

The invention relates to a part (1) for interior trim of a motor vehicle, said part comprising a main layer (2), said layer comprising a thermo-compressed fibrous underlayer (3) based on structural fibers bonded together by a heat-activatable bonding agent and a waterproof underlayer (4) made of plastic material fixed by a fixing face (5) on the reverse side of said fibrous underlayer, said waterproof underlayer being made of thermoplastic elastomer based on styrene-ethylene-butylene-styrene, said part further comprising a set of injection-molded polypropylene-based reinforcing ribs (6) overmolding said waterproof underlayer on its opposite face (7) to said fixing face. Figure 1

Description

Title of the invention: Interior trim part for a motor vehicle

[0001] The invention relates to an interior trim part for a motor vehicle and a method for producing such a part.

[0002] It is known to produce an interior trim part for a motor vehicle, for example in the form of a floor mat or side trim for a luggage compartment, said part comprising a main layer, said layer comprising: - a thermo-compressed fibrous underlayer based on structural fibers bonded together by a heat-activatable bonding agent, - a waterproof underlay fixed by a fixing face on the reverse side of said fibrous underlay.

[0003] The presence of the waterproof underlayer - which is in particular based on ethylene propylene diene monomer (EPDM) - is particularly required so that the part has acoustic insulation properties, in particular when it is implemented in a "spring mass" system by being arranged on a layer of elastically compressible spring.

[0004] However, such a part may have insufficient rigidity, which may lead to a deformation of its geometry in use compared to its nominal geometry.

[0005] One way of overcoming this drawback is to provide an increase in the surface mass of at least one of the sub-layers, but this results in an increase in weight and additional cost of the part which may be excessive.

[0006] The aim of the invention is to propose an arrangement allowing reinforcement of the rigidity of the part at lower cost and weight.

[0007] To this end, and according to a first aspect, the invention proposes an interior trim part for a motor vehicle, said part comprising a main layer, said layer comprising: - a thermo-compressed fibrous underlayer based on structural fibers bonded together by a heat-activatable bonding agent, - a waterproof underlay made of plastic material fixed by a fixing face on the reverse side of said fibrous underlay,

[0008] said part further having the following characteristics: - said waterproof underlay is made of thermoplastic elastomer based on styrene-ethylene-butylene-styrene, - it further comprises a set of injection-molded polypropylene-based reinforcing ribs overmolding said waterproof underlay on its face opposite said fixing face.

[0009] The presence of ribs improves the bending resistance of the part, which stabilizes its geometry during use.

[0010] The use of polypropylene to produce the ribs is dictated by economic considerations and also by the fact that polypropylene has a high rheological fluidity, which allows the easy production of ribs of small width and height.

[0011] Furthermore, reinforcing the rigidity of the part by ribs makes it possible to carry out said reinforcement in a localized manner, only in the zone(s) of the part requiring it, which makes it possible to minimize the cost and weight of said part.

[0012] Furthermore, the applicant noted that the ethylene propylene diene monomer (EPDM) usually used to produce the waterproof underlay did not allow good adhesion between said underlay and the ribs; similarly, the adhesion between the waterproof underlay and the fibrous underlay could prove insufficient.

[0013] Following numerous tests, the applicant turned to a thermoplastic elastomer based on styrene-ethylene-butylene-styrene (SEBS) which made it possible to obtain exceptional adhesion between the waterproof underlayer and the ribs, and also between said waterproof underlayer and the fibrous underlayer.

[0014] Indeed, a peeling effected between the fibrous sub-layer and the waterproof sub-layer causes a “cohesive rupture” resulting in a tearing of said waterproof sub-layer in its thickness; the same is true between the ribs and the waterproof sub-layer, the latter tearing in the same way.

[0015] We will see later that such adhesion on both sides of the waterproof underlayer is optimized when it has been brought to the Vicat temperature (softening) of the SEBS before its thermocompression and during its overmolding by the ribs.

[0016] According to a second aspect, the invention proposes a method for producing such a part.

[0017] Other features and advantages of the invention will appear in the following description, made with reference to the attached figure:

[0018] [Fig. 1] which is a schematic view in partial section of a part before its removal from the mold used to shape it.

[0019] With reference to the figure, a part 1 of interior trim for a motor vehicle is described, said part comprising a main layer 2, said layer comprising: - a thermo-compressed fibrous underlayer 3 based on structural fibers - for example based on glass or polyethylene terephthalate (PET) - bonded between them by a heat-activatable bonding agent - for example in the form of melted polypropylene fibers or bi-component fibers -, - a waterproof underlay 4 made of plastic material fixed by a fixing face 5 on the reverse side of said fibrous underlay,

[0020] said part further having the following characteristics: - said waterproof underlay is made of thermoplastic elastomer - in particular extruded - based on styrene-ethylene-butylene-styrene (SEBS), - it further comprises a set of reinforcing ribs 6 based on injection-molded polypropylene overmolding said waterproof underlayer on its opposite face 7 to said fixing face.

[0021] It is recalled here that bi-component fibers are fibers provided with a core made of thermoplastic material with a high melting point, said core being coated with a sheath made of thermoplastic material with a lower melting point, the melting of said sheath allowing the structural fibers to be bonded together.

[0022] The core may in particular be based on polyester and the sheath based on chemically modified polyester so as to lower its melting point.

[0023] According to one embodiment, the polypropylene is reinforced by the integration of reinforcing fibers - for example glass fibers, at a level of 10 to 30% by weight - or mineral powder - for example talc -, in order to contain shrinkage.

[0024] According to one embodiment, the ribs 6 have a width at the base of the rib (which is the zone of maximum width due to the clearance required for demolding the ribs) of between 1 and 5 mm and a height less than three times said width.

[0025] According to one embodiment, the waterproof underlayer 4 has a surface mass of between 0.07 (which corresponds to a film) and 4 Kg / m2 (which corresponds to a mass layer usable in a “mass-spring” type insulation system).

[0026] According to one embodiment, implemented in particular in the case of high surface masses, the styrene-ethylene-butylene-styrene (SEBS) is provided with a mineral filler - for example based on barite or calcium carbonate.

[0027] According to one embodiment, styrene-ethylene-butylene-styrene (SEBS) has been chemically modified to strengthen the adhesion of polypropylene.

[0028] According to the embodiment shown, the part 1 further comprises a non-woven web 8 - for example polyester - arranged between the waterproof underlayer 4 and the ribs 6, said web having a surface mass of less than 80 g / m2.

[0029] Such an arrangement makes it possible in particular to avoid catching in the mold 11 detailed later, and also to reinforce the mechanical adhesion between the ribs 6 and the waterproof underlayer 4, this by coating the fibers of the web 8 with the polypropylene of said ribs.

[0030] The low surface mass of the web 8 gives it a porosity allowing penetration of the polypropylene into it up to the waterproof sub-layer 4 on which an essentially chemical adhesion takes place.

[0031] According to the embodiment shown, the waterproof underlayer 4 is overmolded by at least one functional member 9 - such as a fixing means - based on injection-molded polypropylene.

[0032] According to the embodiment shown, the fibrous underlayer 3 is coated, opposite the waterproof underlayer 4, with an appearance layer 10 - for example based on carpet.

[0033] The adhesion of the surface layer 10 to the fibrous sub-layer 3 can in particular be achieved by interposing a film or a polyethylene powder brought to its melting temperature.

[0034] A method for producing such a part 1 is now described, said method comprising the following steps: • heating - for example between heating plates or by exposure to infrared radiation - a fibrous underlayer 3 based on structural fibers bonded together by a heat-activatable bonding agent at the activation temperature of said bonding agent, • heat a waterproof undercoat 4 based on styrene-ethylene-butylene-styrene (SEBS), • superimposing said fibrous underlayer on said waterproof underlayer and placing the assembly in a thermocompression mold 11, said mold being provided with injection points 12 and a network of grooves 13 communicating with said injection points and intended to allow the molding of a network of ribs 6, said waterproof underlayer being placed facing said grooves, • carry out thermocompression of said assembly, so as to obtain forming of said assembly and adhesion of said sub-layers to each other, • injecting through said injection points, before cooling below the Vicat temperature - for example of the order of 80°C - of said waterproof underlay, polypropylene, filled or not, so as to create said network of ribs by filling said grooves, said ribs overmoulding said waterproof underlay.

[0035] The Vicat temperature of the waterproof underlay 4 is notably measured according to the protocol described in standard ISO 306 (2013).

[0036] As mentioned above, the injection carried out before cooling of the waterproof sub-layer 4 below its Vicat temperature is required to optimize the adhesion between said sub-layer and the ribs 6, and also between said sub-layer and the fibrous sub-layer 3.

[0037] The use of a single mold 11 to carry out the thermocompression and the injection molding makes it possible to carry out the injection of the polypropylene onto the waterproof underlayer 4 while it is still hot and further simplifies the manufacturing process of the part 1, with the resulting savings.

[0038] It is possible to provide for placing in the mold 11 an appearance layer 10 - for example based on carpet - on the fibrous underlayer 3, opposite the waterproof underlayer 4.

[0039] According to one embodiment, the mold 11 is further provided with at least one impression 14 communicating with an injection point 12, said impression being shaped so as to allow the production of a functional member 9 based on polypropylene overmolding the waterproof sub-layer 4 on its face 7 provided with ribs 6.

[0040] It is also possible to provide for placing in the mold 11 a web 8 of non-woven fabric with a low surface mass (the characteristics of which have been presented above) on the face 7 of the waterproof underlayer 4 intended to receive the ribs 6.

Claims

Claims

1. Part (1) for interior trim of a motor vehicle, said part comprising a main layer (2), said layer comprising: - a thermo-compressed fibrous underlayer (3) based on structural fibers bonded together by a heat-activatable bonding agent, - a waterproof underlayer (4) made of plastic material fixed by a fixing face (5) on the reverse side of said fibrous underlayer, said part being characterized in that: - said waterproof underlayer is made of thermoplastic elastomer based on styrene-ethylene-butylene-styrene, - it further comprises a set of reinforcing ribs (6) based on injection-molded polypropylene overmolding said waterproof underlayer on its opposite face (7) to said fixing face.

2. Part (1) according to claim 1, characterized in that the polypropylene is reinforced by the integration of reinforcing fibers or mineral powder.

3. Part (1) according to one of the preceding claims, characterized in that the ribs (6) have a width at the base of the rib of between 1 and 5 mm and a height less than three times said width.

4. Part (1) according to any one of the preceding claims, characterized in that the waterproof underlayer (4) has a surface mass of between 0.07 and 4 kg / m2.

5. Part (1) according to any one of the preceding claims, characterized in that the styrene-ethylene-butylene-styrene is provided with a mineral filler.

6. Part (1) according to any one of the preceding claims, characterized in that the styrene-ethylene-butylene-styrene has been chemically modified to strengthen the adhesion of the polypropylene.

7. Part (1) according to any one of the preceding claims, characterized in that it further comprises a non-woven web (8). arranged between the waterproof underlay (4) and the ribs (6), said veil having a surface mass of less than 80 g / m2.

8. Part (1) according to any one of the preceding claims, characterized in that the waterproof underlayer (4) is overmolded by at least one functional member (9) based on injection-molded polypropylene.

9. Method for producing a part (1) according to any one of the preceding claims, said method comprising the following steps: • heating a fibrous sub-layer (3) based on structural fibers bonded together by a heat-activatable bonding agent to the activation temperature of said bonding agent, • heating a waterproof sub-layer (4) based on styrene-ethylene-butylene-styrene, • superimposing said fibrous sub-layer on said waterproof sub-layer and placing the assembly in a thermocompression mold (11), said mold being provided with injection points (12) and a network of grooves (13) communicating with said injection points and intended to allow the molding of a network of ribs (6), said waterproof sub-layer being placed opposite said grooves, • carrying out thermocompression of said assembly, so as to obtain a forming of said assembly and an adhesion of said sub-layers to each other,• injecting through said injection points, before cooling below the Vicat temperature of said waterproof underlay, polypropylene, filled or not, so as to create said network of ribs by filling said grooves, said ribs overmolding said waterproof underlay.,

10. Method according to the preceding claim, when it relates to claim 8, characterized in that the mold (11) is further provided with at least one imprint (14) communicating with an injection point (12), said imprint being shaped so as to allow the obtaining of a functional member (9) based on polypropylene overmolding the waterproof underlayer (4) on its face (7) provided with ribs (6).

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