Composite product comprising natural fibres in a matrix, with an outside protective layer made of a polypropylene based compound

Abstract

The present invention concerns a composite product (10) comprising natural fibres (12) in a matrix (14), wherein it further comprises an outside protective layer (20) made of a polypropylene based compound (16) comprising polypropylene as main component, organic UV absorbing additive(s), and light stabilization additive(s) of the family Hindered Amine Light Stabilizers (HALS), wherein said polypropylene based compound has a Melt Flow Rate (MFR) above 4 g / 10mn, and wherein said polypropylene based compound (16) is transparent or translucent. This outside protective layer (20) improves the durability of the composite product (10) in outdoor conditions, notably under UV / visible light exposure.

Description

Composite product comprising natural fibres in a matrix, with an outside protective layer made of a polypropylene based compound Technical domain

[0001] The present invention concerns a thermoplastic natural fibre composite product, namely a product made from or comprising a natural fibre composite or NFC.

[0002] A thermoplastic natural fibre composite is a material that combines natural fibres (such as jute, hemp, flax, kenaf, coir, wood fibres, or even agricultural waste like rice husks) with a thermoplastic polymer matrix (such as polypropylene (PP), polyethylene (PE), polylactic acid (PLA) polyamide 11 (PA11), polyamide 12 (PA12), thermoplastic polyurethane (TPU), polyoxymethylene (POM) or cellulose propionate (CP)).Natural fibres serve as reinforcement, improving the mechanical properties of the composite (like stiffness and strength).Thermoplastic polymers act as a binding matrix, holding the fibres together and allowing the material to be shaped or moulded when heated.

[0003] These thermoplastic natural fibre composites are lightweight, environmentally friendly (due to the use of renewable fibres), and often recyclable, making them a sustainable alternative to traditional plastic or fibreglass-reinforced composites.Thermoplastic natural fibre composites are versatile and can be used in various industries, such as for instance in the following applications :- Automotive Industry :door panels, dashboards, trunk liners, and interior trims due to their lightweight and cost-effectiveness;- Construction and Building Materials : decking, fencing, roofing tiles, and wall panels, offering durability and aesthetic appeal;- Consumer Goods : Furniture, packaging, toys, and sports equipment because they are eco-friendly and safe;- Electronics : casings for laptops, phones, and other gadgets due to their low weight and decent mechanical properties;BCOMP-11-PCT- Transportation and Aerospace : lightweight interior components for airplanes, trains, or ships;- Packaging Materials : sustainable packaging, replacing single-use plastics.

[0004] In more and more industries such natural fibre composites are also chosen for their appearance. This appearance brings several positive advantages, making products made from natural fibre composites (NFCs) increasingly popular in various industries.

[0005] The natural texture and grain of natural fibres like jute, hemp, flax, or coir have a visually appealing texture that provides a unique, organic look. This is highly desirable for applications like furniture, interior panels, and decorative products. The visible presence of natural fibres in natural fibre composites (NFCs) conveys a sense of environmental consciousness and sustainability, which resonates with eco-conscious consumers. The natural fibres themselves provide variability in colour and patterns, making each product unique and often associated with craftsmanship and quality, giving the resulting product a premium appeal. This is particularly appealing for high-end products. Unlike the sterile, uniform appearance of traditional plastics, natural fibre composites (NFCs) have a warm, natural and inviting look that enhances the product's tactile and visual appeal.

[0006] When these products made from natural fibre composites are exposed to outdoor conditions, several problems can arise over time.Thermoplastic natural fibre composites are prone to certain degradative effects when exposed to environmental factors like rain, sunlight, temperature fluctuations, and moisture.

[0007] Some common issues include:- UV degradation (or more generally degradation under sunlight, which includes UV and visible light): Prolonged exposure to sunlight causes the thermoplastic matrix to degrade, leading to discoloration, brittleness, and a loss of mechanical properties. This is due to alteration of the molecularBCOMP-11-PCTchains due to the free radical creation from the light energy.Natural fibres themselves also degrade under UV / visible light radiation because of their organic composition composed of cellulose, hemi-cellulose, and lignin, being polymer themselves, and the chemical reactions triggered by UV / visible light.- Moisture absorption: natural fibres are hydrophilic (absorb water), which can lead to swelling or dimensional instability, fungal growth or mould due to retained moisture and degradation of fibre-matrix adhesion, reducing overall strength. Also, natural fibres can be prone to attack by microorganisms (e.g., fungi, bacteria, termites) in humid or moist conditions, leading to deterioration- Thermal cycling : repeated heating and cooling cycles in outdoor environments may lead notably to microcracking in the matrix or at the fibre-matrix interface, and deformation or warping of the product over time.- Reduced mechanical performance : over time, the combined effects of UV / visible light degradation, moisture, and thermal stresses lead to weakened mechanical performance (e.g., lower tensile strength, stiffness, and impact resistance).- Biological Degradation : colour fading and aesthetic changes.Moreover, exposure to UV / visible light and / or rain may cause loss of the original appearance, making the product look aged.

[0008] Finally, products made from natural fibre composites are also subject to surface deterioration in appearance, particularly scratches, as a result of repeated contact and impact.Related art

[0009] To improve the durability of natural fibre composites in outdoor conditions, notably under UV / visible light exposure, manufacturers can implement the following strategies:- Surface treatments for fibres : Applying chemical treatments to natural fibres (e.g., silane coupling agents, acetylation or alkali treatment:) toBCOMP-11-PCTreduce moisture absorption and enhance bonding with the matrix;- Surface coatings for fibres : applying protective coatings or resins (e.g., polyurethane, epoxy) filters UV / visible light and prevent water ingress; - UV stabilizers and additives :Adding stabilizers, antioxidants, or UV-blocking agents to the thermoplastic matrix to slow down degradation caused by sunlight;- Blending with synthetic fibres : Combining natural fibres with synthetic fibres (e.g., glass or carbon fibres) to improve resistance to weathering (reduction of the overall sensitivity to sunlight and moisture).

[0010] To improve the scratch resistance of products made from thermoplastic natural fibre composites (NFCs), material modifications, surface treatments, and coatings can be applied, with the following non-limitative possible routes:- Applying a thin, durable scratch-resistant coating such as polyurethane, epoxy or UV-cured coatings;- use of additive or fillers in the thermoplastic matrix : fillers like calcium carbonate, talc, or silica can harden the surface, impact modifiers (e.g., elastomers) increase the material's toughness and flexibility, anti-scratch agents (e.g., certain silicones or waxes) reduce the coefficient of friction; - select a harder thermoplastic matrix : Opting for harder thermoplastics like polyamide (nylon) or polycarbonate or combining softer thermoplastics (like polypropylene) with harder ones;- Applying a protective paint layer or a thin plastic overlay (e.g., laminate or thermoplastic sheet) can shield the surface from scratches.

[0011] In some markets, there are high standards for thermoplastic natural fibre composites that provide both structural reinforcement and a decorative outside layer. Such markets include automotive interior applications, where some parts made from thermoplastic natural fibre composites must meet all the durability standards for that market, such as light resistance, heat resistance, moisture resistance, scratch resistance, etc. When these parts are also decorative, there exist an additional requirement to keep the natural fibre reinforcement visible over time, so theBCOMP-11-PCTthermoplastic used as the matrix must be and stay transparent or at least translucent.

[0012] The sum of these constraints is a real challenge, for which no efficient solution has yet been proposed.Short disclosure of the invention

[0013] An aim of the present invention is the provision of a product made from thermoplastic natural fibre composite that overcomes the shortcomings and limitations of the state of the art.

[0014] Another aim of the invention is to provide a composite product from thermoplastic natural fibre that provides durability through high level resistance, notably to UV / visible light and also possibly scratches, and that allows to see the natural fibre reinforcement.

[0015] Another aim of the invention is to provide a composite product from thermoplastic natural fibre which is easy to be processed at competitive cost.

[0016] According to the invention, these aims are attained by the object of the attached claims, and especially by a composite product comprising natural fibres in a matrix, wherein it further comprises an outside protective layer made of a polypropylene based compound comprising: - polypropylene as main component,- organic UV absorbing additive(s), and- light stabilization additive(s) of the family Hindered Amine Light Stabilizers (HALS), notably NOR-HALS (n-alkoxy HALS), ,wherein said polypropylene based compound has a Melt Flow Rate (MFR) above 4 g / 10mn , andwherein said polypropylene based compound is transparent or translucent.BCOMP-11-PCT

[0017] With respect to what is known in the art, the invention provides the advantage that the polypropylene-based compound used as an outside protective layer of the composite product is really efficient for UV resistance while not preventing the visibility of the natural fibres. In the present text "UV resistance" means keeping intact or almost identical the mechanical properties of the product when exposed to UV / visible light also with keeping the transparent / translucent feature allowing to see the natural fibre, and a very moderate colour change of the product.

[0018] This allows to keep the natural visual appearance of the product, whether the natural fibres contained in the matrix are used only for their aesthetic properties or are used both for their aesthetic and mechanical reinforcement properties.

[0019] In possible embodiments of the composite product, the matrix also comprises a polypropylene based compound as defined previously. Such a polypropylene based compound comprises:- polypropylene as main component,- organic UV absorbing additive(s), and- light stabilization additive(s) of the family Hindered Amine Light Stabilizers (HALS), notably NOR-HALS,wherein said polypropylene based compound has a Melt Flow Rate (MFR) above 4 g / 10mn, and wherein said polypropylene based compound is transparent or translucent.Those versions with a polypropylene based compound as outer layer and further as matrix of the body of the composite product allows emphasized resistance to visual and mechanical deterioration due to outdoors aggression and aging.Among those versions, according to a second embodiment of the composite product, the polypropylene based compound forming the outside protective layer of the composite product is the same as the polypropylene based compound forming the matrix of the body of the composite product.Among those versions, according to a third embodiment of the composite product, the polypropylene based compound forming the outsideBCOMP-11-PCTprotective layer of the composite product is different from the polypropylene based compound forming the matrix of the body of the composite product, which means having a different composition.

[0020] The use of polypropylene in the polypropylene-based compound further allows the use of a bio-based raw materials (such as used-cooking oils), which allows to use an almost entirely bio-based solution. The development of such biopolymers is on-going and allows to use recycled polymers as an input material.Natural fibres sequestrate a non-negligible amount of CO2 from the atmosphere during the growth phase of the plant, which allows to have a negative global warming potential (GWP) for some products containing a high percentage of natural fibres.

[0021] In addition, the production of parts with a high-performance composite material, which combines the excellent properties of a fabric made from natural fibres such as flax with a suitable impregnation with a polymer forming the thermoplastic matrix, allows a significant reduction in weight compared to existing solutions with injected plastics such as polycarbonate / acrylonitrile butadiene styrene (PC-ABS). Lighter parts mean that the proportion of polymer is reduced even further, thus limiting the depletion of fossil resources.Furthermore, through the choice of polypropylene, the use of polypropylene based compound will enable and facilitate the recycling process at the end of the use phase of the composite product.All these arguments make the use of natural fibre-based composites a very interesting alternative to current solutions in many industries, such as the automotive industry.

[0022] In a possible embodiment of the composite product, the outside protective layer made of said polypropylene based compound has a minimum thickness which is in the range of 5 to 500 pm, preferably between 20 to 500 pm, preferably between 100 to 300 pm, and more preferably between 50 to 200 pm.BCOMP-11-PCTThis outside protective layer without natural fibres can have a heterogeneous thickness but a minimal thickness contributes to obtaining the required resistance, notably to scratch and to UV / visible light degradation.

[0023] In a possible embodiment of the composite product, the polypropylene of said polypropylene based compound is a random copolymer or a homopolymer.When the polypropylene of said polypropylene based compound is a random copolymer, this random copolymer can be notably obtained by polymerisation of a mixture of propylene with ethylene or by polymerisation of a mixture of propylene with butene. This can be applied either for the polypropylene-based compound of the outside protective layer or for the polypropylene-based compound of the matrix, and also for both.Using a random copolymer or a homopolymer polypropylene grade instead of a heterophasic copolymer polypropylene grade in the polypropylene-based compound is preferred to avoid the scratch whitening and have the outside protective layer more scratch resistant. Some additives can be added in the outside protective layer forming the external wear and / or decorative surface of the composite product and hinder the apparition of scratches (whitening of the scratches).

[0024] The viscosity of the polypropylene-based compound must be low enough to enable a good surface quality when processed in compression moulding. The polypropylene-based compound is transparent or translucent. The choice of polypropylene grade has notably an influence on improvement of the scratch resistance properties, but also on the resistance to UV / visible light, clarity or transparency of the polypropylene-based compound, and on the quantity of volatile organic compounds (VOC) emissions.

[0025] The Melt Flow Rate (MFR) of the polypropylene-based compound must be high enough to perform an easy and rapid processing, notablyBCOMP-11-PCTwhen processed in compression moulding. The polypropylene-based compound has preferably a Melt Flow Rate (MFR measured at 230°C, under 2.16 kg load following the ISO 1133-1 standard) higher than 5 g / 10 min, preferably a Melt Flow Rate higher than 10 g / 10 min.

[0026] Depending on the moulding process and parameters, and also on the application of the composite product (decorative and structural requirements or only decorative purpose), a different viscosity range can be selected.Preferably, the Melt Flow Rate (MFR) of the polypropylene based compound is between 10 and 200 g / 10 min.In a first option, the Melt Flow Rate (MFR) of the polypropylene based compound is between 10 and 30 g / 10 min.In a second option, the Melt Flow Rate (MFR) of the polypropylene based compound is between 30 and 100 g / 10 min.In a third option, the Melt Flow Rate (MFR) of the polypropylene based compound is equal to or above 100 g / 10 min.

[0027] In the second and third embodiments where the matrix of the body of the composite product comprises or is formed by said polypropylene-based compound, the natural fibres are impregnated with a polypropylene grade, which is sufficiently fluid in the molten state to be able to penetrate the fibres well enough. Therefore, the Melt Flow Rate (MFR) of the polypropylene-based compound can be above 30 g / 10 min, and notably as respectively mentioned in the above mentioned second and third options, between 30 and 100 g / 10 min or equal to or above 100 g / 10 min.

[0028] In all embodiments, considering the outside protective layer made of the polypropylene-based compound, the viscosity requirement of the polypropylene depends on the temperature parameters used for the compression moulding, and not on the impregnation of the natural fibres. Therefore, the Melt Flow Rate (MFR) of the polypropylene-basedBCOMP-11-PCTcompound can be between 10 and 200 g / 10 min, and notably as in the above mentioned first option, between 10 and 30 g / 10 min.

[0029] The polypropylene-based compound can contain in addition an adhesion promoter or coupling agent ensuring a good compatibility with natural fibres, usually provided in a masterbatch, in low quantities (preferably with a masterbatch content of less than 10% by weight), including one or several of the following : maleic anhydride-modified polypropylene (maPP), and glycidyl methacrylate modified polypropylene.

[0030] In the second and third embodiments where the matrix of the body of the composite product comprises or is formed by the polypropylene-based compound defined in the present text, the natural fibres have to be well impregnated with the polypropylene-based compound.In other embodiments where the matrix of the body of the composite product comprises or is formed by another compound than the polypropylene-based compound defined in the present text, including virgin polypropylene or another polymer or material containing polypropylene, there also exist a need of promote the compatibility between the polymer and the natural fibres.Since natural fibres are highly hydrophilic, while virgin polypropylene is non-polar, the polypropylene chains can better impregnate if modified chemically. To that end, some adhesion promoters, called maleic anhydride that are grafted to the polypropylene chains can be used. These functional groups help for the bonding of the matrix to the reinforcement material. This forms anhydride-modified polypropylene (maPP). The grafting of the maleic anhydride to the polypropylene chains is normally made with the help of peroxide chemicals. In general, the grafting process is done in a first step in order to obtain a masterbatch. This is because pure maleic anhydride (MA) can interact with other additives, such as UV additives, and interfere with their protective action.BCOMP-11-PCT

[0031] According to the invention, the polypropylene-based compound comprises organic UV absorbing additive(s) also called UV blocking additives. This or these UV absorbing additive(s) is / are absorbing UV light and converting it into heat, preventing the natural or artificial UV light from causing damage to the polymer and the natural fibres. This provides the polypropylene-based compound an enhanced resistance to light aggression, and allows the outside protective layer made from that polypropylene based compound to protect the material laying below.The following possible UV absorbing additive(s) can be used alone or in combination: organic benzotriazole (BZT), hydroxyphenyl triazine (HPT), cyanoacrylate UV-absorber and hydroxy benzophenone UV-absorber.Preferably, when using one or several as UV absorbing additive(s), the total quantity in said polypropylene based compound can be equal to or above 0.2% weight, or in the range between 0.2% to 5% weight, notably in the range 0.2 to 1.5% weight.

[0032] In some embodiments, in addition to organic UV absorbing additive(s), the polypropylene-based compound comprises inorganic UV-absorbing additive(s) such as TiCh or ZnO particles, notably nanoparticles.

[0033] According to the invention, the polypropylene-based compound comprises light stabilization additives of the family Hindered Amine Light Stabilizers (HALS). HALS do not significantly absorb UV / visible light radiation, but inhibit degradation of the polymer by cyclically removing free radicals that are produced by photo-oxidation of the polymer, preventing the natural or artificial light, including UV light, from causing damage to the polymer.This provides stabilization against UV / visible light and against oxidation. This provides the polypropylene-based compound an enhanced resistance to light and atmosphere aggression.This / these light stabilization additive(s) of the family Hindered Amine Light Stabilizers (HALS) is possibly present above 0.05% weight.These light stabilization additives can comprise High molecular weight Hindered Amine Light Stabilizers, in particular High molecular weight NOR Hindered Amine Light Stabilizers.BCOMP-11-PCTPreferably, this High molecular weight Hindered Amine Light Stabilizer is in the range between 0.05% to 2% weight.In the present text, «High molecular weight" means a molecular weight equal to or more than 1000 g / mol.These light stabilization additives can comprise Low molecular weight Hindered Amine Light Stabilizers, in particular Low molecular weight NOR Hindered Amine Light Stabilizers.Preferably, this Low molecular weight Hindered Amine Light Stabilizer is in the range between 0.05% to 2% weight.In the present text, "Low molecular weight" means a molecular weight less than 1000 g / mol.These light stabilization additives can comprise High molecular weight Hindered Amine Light Stabilizers and Low molecular weight Hindered Amine Light Stabilizers.These light stabilization additives can comprise High molecular weight Hindered Amine Light Stabilizers and Low molecular weight NOR Hindered Amine Light Stabilizers.These light stabilization additives can comprise High molecular weight Hindered Amine Light Stabilizers and High molecular weight NOR Hindered Amine Light Stabilizers.These light stabilization additives can comprise High molecular weight NOR Hindered Amine Light Stabilizers and Low molecular weight NOR Hindered Amine Light Stabilizers.When both High molecular weight (NOR) HALS and Low molecular weight (NOR) HALS are present, the total quantity is preferably in the range between 0.05 to 3% weightNOR Hindered Amine Light Stabilizers present a better durability than traditional HALS especially in acidic environment, and have good synergistic effects with UV absorbers.

[0034] In some embodiments, the polypropylene-based compound further comprises one or several of the following: antioxidant stabilizer, notably phenolic antioxidant stabilizer, and processing stabilization additive, notably phosphite and / or phosphonite processing stabilizer.Antioxidants are added to the recipe for the stabilization during theBCOMP-11-PCTprocessing of the polypropylene-based compound.The antioxidant stabilizer is preferably in the range between 0.01-0.4% weight.The processing stabilization additive is preferably in the range between 0.02-0.4% weight.

[0035] The stabilization additives can be supplied as masterbatches (meaning the additives are diluted in a polymer, such as polypropylene) or directly as pure substances.

[0036] In addition to or instead of UV absorbing and / or stabilizing additives, some provisions can be implemented for UV / visible light protection of the natural fibres.Natural fibres can be protected against UV / visible light damage while keeping their natural colour or appearance through a transparent photostabilizer present on the natural fibres, preventing the light induced discoloration, and the photo-oxidation of the lignin, present in the natural fibres.In other cases, natural fibres can be protected against UV / visible light damage without keeping their natural colour through bleaching of the natural fibres and / or dyeing of the natural fibres, with colourants comprising at least one among organic dyes and organic or inorganic pigments, preventing the light induced discoloration, and the photooxidation of the lignin, present in the natural fibres.

[0037] In possible embodiments, said polypropylene based compound further comprises colouring additive(s) and / or colourant(s), so that said polypropylene based compound is coloured but is kept translucent. This allows the natural fibres to stay somehow visible and to keep the appealing natural fibre appearance.

[0038] To improve the scratch resistance properties of the outside protective layer, random copolymer or homopolymer polypropylene is preferred as polymer basis.BCOMP-11-PCTAlso, in some embodiments, the polypropylene-based compound further comprises one or several of the following as anti-scratch additive(s): an inorganic scratch improver additive, notably a silica based inorganic scratch improver additive, and an organic scratch improver additive, notably a silicone based organic scratch improver additive.

[0039] The polypropylene-based compound has generally a melting point between 120°C and 200°C.

[0040] In possible embodiments, the composite product further comprises a substrate supporting the natural fibres impregnated by the matrix. In that situation, the natural fibres impregnated by the matrix is a layer located between the substrate and the outside protective layer.For instance, such substrate is a composite layer made of a natural fibre woven or non-woven fabric impregnated with thermoplastic resin, or a polymeric compound.Short description of the drawings

[0041] Exemplar embodiments of the invention are disclosed in the description and illustrated by the drawings in which:Figure 1 illustrates schematically a section of a composite product according to the prior art, under UV / visible light;Figure 2 illustrates schematically a section of a composite product according to the present invention, in a first embodiment;Figure 3 illustrates schematically a section of a composite product according to the present invention, in a second embodiment;Figure 4A is a picture of a section of a composite product according to the present invention, Figure 4B is a representative sketch ofBCOMP-11-PCTpicture of Figure 4A, Figure 4C is a schematic and theoretical representation of the cross-section of a composite product, similar to that shown in Figure 4A; andFigure 5 is a sketch of a seatback for a car seat formed by a composite product according to the present invention.Examples of embodiments of the present invention

[0042] With reference to Figure 1, a section of a composite product 10 comprising stacked layers of natural fibres 12 alternating with a matrix 14 which has also impregnated the natural fibres 12 is schematically shown.

[0043] When outdoor exposed, the composite product 10 will suffer degradation under UV / visible light (see Figure 1). Under high UV irradiance, the polymeric matrix is subject to a breakage of the molecular chains due to the free radical creation from the light energy. The consequences of this are a loss of mechanical properties, and most importantly a shift in the visual appearance, often visible by a whitening of the surface, which becomes opaque and hazy when originally transparent or translucent. Also, the natural fibres are also sensitive to the environment. Natural fibres are composed of cellulose, hemi-cellulose, and lignin, being polymer themselves. The UV-exposed natural fibres will endure a change in visual appearance as well, resulting in a brighter colour. Furthermore, the mechanical properties of the composite material may be degraded on UV-aged natural fibres.

[0044] In a first embodiment shown in Figure 2, a polypropylene based compound 16 as defined in the present text forms an outside protective layer 20, on the top of the composite product 10. This outside protective layer 20 is located above the stacked layers of natural fibres 12 impregnated with the matrix 14. The main part or body of the composite product 10 made from natural fibre composite 12+14 can have as polymer matrix also a polypropylene compound, such as a homopolymerizedBCOMP-11-PCTpolypropylene or a mixture of polypropylene with maleic anhydride-modified polypropylene (maPP), or alternatively the impregnation polymer can be any thermoplastic polymer, notably polyamide 11 (PA11), polyamide 12 (PA12), thermoplastic polyurethane (TPU), cellulose propionate (CP) or Polylactic acid (PLA), taken alone or in combination.

[0045] In the present text, the composite product 10 comprises three elements:- natural fibres 12 for reinforcement and / or decorative purpose,- a matrix formed by an impregnation polymer compound impregnating the natural fibres (designated as matrix 14 or by polypropylene based compound 16 depending on the embodiment to be considered among the first, second and third embodiment) , and- an outside protective layer 20 made of a polypropylene based compound 16 forming a protective polymer.This assembling of three elements constitutes a composite material, either forming an intermediate part which will be further treated, cut, or adjoined to (an)other material(s) / layer(s) / part(s) before constituting the final product, or constituting the final product.

[0046] According to the first embodiment, the thermoplastic natural fibre composite made of these three components can be manufactured in the following way: both impregnation polymer compound (matrix 14) and protective polymer (polypropylene based compound 16) are in the form of films. They are heat laminated with the natural fibres 12 in a press, or continuously in a double belt press.

[0047] Alternatively, impregnation polymer (matrix 14) or protective polymer (polypropylene based compound 16) or both can be in the form of powder, which is scattered on the natural fibres 12 and then heat laminated in a press, or continuously in a double belt press.

[0048] According to another alternative, impregnation polymer (matrix 14) or protective polymer (polypropylene based compound 16) or both canBCOMP-11-PCTbe extruded in-line, and continuously heat laminated with a natural fibres arrangement such as a fabric in a double belt press.

[0049] Alternatively, the impregnation polymer (matrix 14) can be made of polymer fibres mixed or comingled with the natural fibres 12.

[0050] Once laminated, the composite material is conditioned as rolls or sheets of pre-impregnated material (organosheets). This impregnated composite material is an intermediate step in the manufacturing process. When the composite product 10 is used as a surface layer, possibly a decorative layer, it should be combined with a substrate 30, or used as monolithic material (with several plies, having selected fibres orientations). When such substrate 30 is a fibre mat or fabric composite layer, before implementation of the forming step, such substrate 30 is stacked with the composite material made from the three elements with the outside protective layer 20 placed in opposite side with respect to the substrate 30, and this stack is then placed in the press. The fibre composite substrate 30 (see figures 4A and 4B) is typically composed of a non-woven natural fibres layer impregnated with thermoplastic resin, for instance polypropylene. This non-woven natural fibres composite layer can have different grammages depending on the targeted part to be manufactured. Another possible substrate 30 is an injected polymeric compound.

[0051] The composite material with these three elements and the fibre substrate 30 can be processed in a thermo-compression step (or stamp forming process) to fix the final shape and mechanical properties. The composite material is first pre-heated in a convection oven, l-R oven, contact heater,... above the melting point of the matrix. The pre-heating temperature should be controlled and not too high to avoid degradation of the natural fibres 12. The heated composite material is then transferred to a press in a closed 3-D mould, and the pressure is applied to give the shape to the final product. Scrap edges can be cut directly in-mould or in a second step. Additionally, attachments or retainers, can be over injected directly in-mould or added in a second step.BCOMP-11-PCT

[0052] In a second embodiment shown in Figure 3, there is also a polypropylene based compound 16 as defined in the present text, which forms an outside protective layer 20, on the top of the composite product 10, and this same polypropylene based compound 16 further forms the matrix impregnating the stacked layers of natural fibres 12.

[0053] In this second embodiment, the same and single polypropylene-based compound 16 forms the outside protective layer 20 and the matrix of the main part or body of the composite product 10. This polypropylene based compound 16 can be initially prepared as a powder. The other above-mentioned processes can be considered too (film, comingled, in-line extrusion or combinations).

[0054] For the second embodiment and for the third embodiment, the polypropylene based compound 16 has a low viscosity for proper impregnation of the natural fibres 12 and to enable a good surface quality when processed in compression moulding. This polypropylene based compound 16 has a melting point below 200°C.

[0055] In a possible implementation of the second embodiment and of the third embodiment, this polypropylene-based compound 16 has some or all the following features.It is made of a random copolymer or homopolymer polypropylene with a Melt Flow Rate (MFR) that can be between 20 to 150 g / 10min (at 230°C, 2.16 kg load following the ISO 1133-1 standard), preferably 40 to 130 g / 10min. It is stabilized against UV / visible light and oxidation with additives of the family Hindered Amine Light Stabilizers (HALS) (possibly 0.05 % to 2 % weight, preferably 0.15 to 1 % weight). For the stabilization during the processing of the material, it can contain: phenolic antioxidant stabilizers (possibly 0.01 to 0.4% weight) and / or phosphite processing stabilizers (possibly 0.02 to 0.4% weight). It contains UV blocking additives, preferably of the family hydroxyphenyl triazine UV-absorber (possibly 0.2 to 1.5% weight). To ensure a good compatibility with natural fibres, adhesionBCOMP-11-PCTpromoters such as maleic anhydride-modified polypropylene (maPP) can further be used.

[0056] According to the third embodiment, the thermoplastic natural fibre composite made of the above mentioned three components can be manufactured in same possible ways as in the first embodiment, considering the matrix 14 impregnating the natural fibres 12 is replaced by a matrix comprising or formed by a polypropylene based compound 16.

[0057] The natural fibres can be made of any of the following fibres or a combination thereof: flax, hemp, sisal, jute, abaca, kenaf, nettle, ramie, henequen, pineapple, banana, and palm. Flax is a good option for natural fibres used in the composite product 10 according to the invention.The natural fibres can also be manmade cellulosics also named manmade cellulosic fibres (MMCFs). They are regenerated fibres made from natural plant materials, usually from the dissolved wood pulp or "cellulose" of trees.

[0058] In the composite product 10 according to the invention, the arrangement of natural fibres 12 comprises several stacked layers of natural fibres, wherein said layers of natural fibres can form a nonwoven fabric or a woven fabric or a non-oriented natural fibres layer. These layers can also be formed by a unidirectional reinforcement or a mat made of natural fibres. These stacked layers of natural fibres form thereby together for instance a weave, a multi-axial fabric, a non-crimp fabric or a unidirectional fabric.

[0059] The natural fibres 12, when woven in specific architectures, are a key component in the composite material of the main part or body of the composite product 10 and increase considerably its mechanical properties. Unlike short fibres reinforced plastic made with injection moulding, the long fibres allow for high performance materials through compression moulding process, while in addition reducing the weight of the composite product 10, and therefore the amount of plastic material.BCOMP-11-PCT

[0060] Natural fibres being intrinsically UV / visible light sensitive, they can be protected on their own. This can be done by different means, keeping the transparency or translucency of the matrix, and the aesthetics of the fibres. The first solution is by bleaching and / or dyeing the fibres with a UV-stable dye. Then, the UV sensitive components of the natural fibres are partly removed or hidden behind the dye pigments. The second option is by stabilizing the fibres against UV / visible light with a transparent treatment applied to the yarns made from natural fibres. Lignin-stabilizing additives can be used, such as "Lignostab" (Registered Trademark) which is a photo-stabilizer, preventing the UV-light induced discoloration, and the photo-oxidation of the lignin, present in the natural fibres. A silane treatment can also be applied, such as Enovik Dynasylan SIVO 214.

[0061] The impregnation polymer forming the matrix (14 or 16) impregnating the stacked layers of natural fibres 12 has a melting point below 200°C, in order to maintain the good properties of the natural fibres. A long exposition above 200°C would degrade the natural fibres. The viscosity of the impregnation polymer has to be low enough to enable a good impregnation of the natural fibres.

[0062] In Figures 4A and 4B, there is a view of a cross section of a real assembly made of a composite product 10 according to the second embodiment, after compression under heat, with a substrate 30 formed by a non-woven natural fibre composite. This assembly forms a composite product 10'.Here the natural fibres 12 are flax fibres arranged in a twill 2 / 2 fabric made of low-twist yarns.The top portion of the composite product 10' formed by the outside protective layer 20 made from polypropylene-based compound 16, has a thickness a. This thickness a of the outside protective layer 20 can be irregular along the surface of the composite product 10'. Since the fabric formed by the natural fibres 12 has an irregular topography, the thickness of the outside protective layer 20 made from polypropylene-based compound 16 above the flax fibres 12 fluctuates over the surface of the outside protective layer 20 made from polypropylene-based compound 16,BCOMP-11-PCTas shown in Figures 4A and 4B.If there were no polypropylene-based compound 16 above the natural fibres 12, UV / visible light could affect the fibres without possibility to be absorbed in the polypropylene-based compound 16 forming the matrix, which would not be able to protect the fibres from discoloration. In addition, the fibres would be more easily affected by scratches, which could make the latter more visible.With an outside protective layer 20 made from polypropylene-based compound 16 with a minimum thickness a, which is in the range of 5 to 500 pm or 20 to 500 pm, preferably between 100 to 300 pm, and more preferably between 50 to 200 pm, there is sufficient protection of the natural fibres 12.The main part or body of the assembly formed by the composite product 10' shown in figures 4A and 4B (low portion of thickness c) is made by the substrate 30 (non-woven natural fibre composite). Between the substrate 30 and the outside protective layer 20, there is the polypropylene-based compound 16 as matrix impregnating flax fibres 12 of fabric, with a thickness b. This thickness b_can be any thickness, very likely in the range 200-1000 pm. Figure 4C schematically and theoretically represents the crosssection of such an assembly, where thicknesses a, b and c correspond, respectively, to the outside protective layer 20, the flax fibres 12 impregnated with the polypropylene-based compound 16 and the substrate 30. As shown in Figure 4C, the thicknesses a, b and c remain relatively constant throughout the assembly.Examples

[0063] In all the following examples, natural fibres 12 are formed by a flax fabric, the natural fibres 12 being bleached, and then dyed in grey.

[0064] Example 1 : First embodiment (polypropylene based compound 16 for outside protective layer 20 as in Figure 2).Matrix 14 compound:BCOMP-11-PCTo homopolymerized polypropylene with a Melt Flow Rate (MFR) of 50 g / 10 min, mixed witho between 2 and 10% weight maleic anhydride-modified polypropylene (maPP) masterbatch.- Transparent polypropylene-based compound 16 with additives as outside protective layer 20:o homopolymerized polypropylene with a Melt Flow Rate (MFR) of 12 g / 10 min, mixed witho between 0.05% to 2% weight Low Molecular weight NOR HALS,o between 0.05% to 2% weight High Molecular weight HALS, o between 0.2% to 1.5% weight UV absorber, hydroxyphenyl triazine class.- Minimum thickness of the outside protective layer 20 above the flax fibres: around 200 micrometres.- The resulting composite product is a plate exposed to light in a UV / visible light chamber for 510 hours.o Result of this UV / visible light aging test: low discoloration of the composite and low degradation of the polypropylene-based compound 16 above the fibres: Colour change measurement dE*= ~3. (Not the same test as for the next example, for which the test is harsher, leading to higher dE*).

[0065] Example 2: Second embodiment (polypropylene based compound 16 both for outside protective layer 20 and as matrix for the natural fibres 12, as in Figure 3).- Transparent polypropylene based compound 16 with additives as follows:o homopolymerized polypropylene with a Melt Flow Rate (MFR) of 50 g / 10 min, mixed witho between 0.05% to 2% weight Low Molecular weight NOR HALS,o between 0.05% to 2% weight High Molecular weight HALS, o between 0.2% to 1.5% weight UV absorber, hydroxyphenyl triazine class,o between 2 and 10% weight maleic anhydride-modified polypropylene (maPP) masterbatch.BCOMP-11-PCT- Minimum thickness of the outside protective layer 20 above the flax fibres: Between 70 and 200 micrometres.- The resulting composite product is a plate exposed to light following the standard SAE J2412 (250 kJ / m2).o Result of this UV / visible aging test: limited discoloration of the composite and low degradation of the polypropylene-based compound 16 of the outside protective layer 20 above the fibres, except for visible white lines following the direction of yarns for some samples. Colour change measurement: dE*= between 6 and 11.

[0066] Example 3: For comparison, a reference composite product without UV / visible light protection (not according to the invention) was tested.- Transparent polypropylene based compound with additive as follows:o homopolymerized polypropylene with a Melt Flow Rate (MFR) of 50 g / 10 min, mixed witho between 2 and 10% weight maleic anhydride-modified polypropylene (maPP) masterbatch.- The resulting composite product is a plate exposed to light following the standard SAE J2412 (250 kJ / m2).- Result of the UV / visible light aging test: strong discoloration of the composite and degradation of the polypropylene compound above the fibres. Colour change measurement: dE*= ~32.

[0067] Example 4: Second embodiment (polypropylene based compound 16 both for outside protective layer 20 and as matrix for the natural fibres 12, as in Figure 3).- Transparent polypropylene-based compound 16 with additives as follows:o homopolymerized polypropylene with a Melt Flow Rate (MFR) of 125 g / 10 min, mixed witho between 0.05% to 2% weight Low Molecular weight NOR HALS,o between 0.05% to 2% weight High Molecular weight HALS,BCOMP-11-PCTo between 0.2% to 1.5% weight UV absorber, hydroxyphenyl triazine class,o between 2 and 10% weight maleic anhydride-modified polypropylene (maPP) masterbatch.- Minimum thickness of the outside protective layer 20 above the flax fibres: Between 100 and 250 micrometres.- The resulting composite product is a plate exposed to following the standard PV 1303 (5 cycles).o Result of this UV / visible light aging test: low discoloration of the composite and low degradation of the polypropylene-based compound 16 above the fibres, except for visible white lines which appeared due to the test, following the direction of yarns. Colour change measurement dE*= ~3 to 4.

[0068] Example 5: Second embodiment (polypropylene based compound 16 both for outside protective layer 20 and as matrix for the natural fibres 12, as in Figure 3).- Transparent polypropylene based compound 16 with additives as follows:o Random copolymer polypropylene with a Melt Flow Rate (MFR) of 100 g / 10 min, mixed witho between 0.05% to 2% weight Low Molecular weight NOR HALS,o between 0.05% to 2% weight High Molecular weight HALS, o between 0.2% to 1.5% weight UV absorber, hydroxyphenyl triazine class,o between 2 and 10% weight maleic anhydride-modified polypropylene (maPP) masterbatch.- Minimum thickness of the outside protective layer 20 above the flax fibres: Between 50 and 250 micrometres.- The resulting composite product is a plate exposed to light to following the standard PV 1303 (5 cycles).o Result of this UV / visible aging test: limited discoloration of the composite and low degradation of the polypropylene-based compound 16 of the outside protective layer 20 above the fibres, with no visible white lines appearing due to the test. Colour change measurement: dE*= ~1.BCOMP-11-PCT

[0069] The compressed composite product 10 (10' or 10") must withstand several requirements from the interior automotive industry. A non-exhaustive list is given below. These correspond to the most critical tests, because of the materials used in this invention, that are sensitive to some environments.

[0070] Notably, one or several of the following tests is / are used:- UV / visible light aging : test method according to standard SAE J2412 or PV1303;- Scratch resistance : test method according to PV3952 or TL226;- Humid-heat aging : test method according to PV1200;- Heat aging : test method according to TL226;- Fogging : ISO 6452 (VCS 1027.2719-G), requirement < or = 0.3 mg;- Volatile organic compounds (VOC) emissions, Fogging and Odour: test methods according to VW 50180.

[0071] In variants of composite products as given in above examples 1 and 2, a homopolymerized propylene with a Melt Flow Rate (MFR) of 125 g / 10 min is used. The use of such homopolymerized propylene grade with a high Melt Flow Rate (MFR) facilitates the thermocompression.

[0072] The composite product 10, 10' or 10" according to the present invention is forming a thermoplastic natural fibre composite mostly convenient as decorative and structural component notably for automotive interior.

[0073] The composite product 10, 10' or 10" according to the present invention can, for instance and in a non-limitative way, form any of the following parts or a portion of any of the following parts : an automobile body part, in particular a car seat, a part of car interior, a car instrument panel, a car console panel, a car door panel, a car armrest, a car headliner, a car interior trim, a car dashboard, a car centre console, a car pillar trim, a car trunk trim, a car roof, a car hood, a car fender, a car spoiler, a car front or rear bumper, a car aerodynamic kit;BCOMP-11-PCT- a sport article, in particular a canoe, a kayak, a light boat hull, a rod saddle, a bicycle saddle, a bicycle frame, a bicycle handlebar, a baseball bat, a paddle, a ski or walking stick;- an element of furniture or a part of the interior of an airplane, in particular a side panel, a ceiling panel, a luggage compartment; and an aerodynamic part of a light airplane, in particular an engine cowling, a wheel cowling; and an aerodynamic fairing of a mobile machine.

[0074] Figure 5 illustrates an example for a composite product according to the invention. In this example, the composite product 10" is forming a seatback for a car seat or a portion thereof. A seatback has to resist well impacts and airbag deployment in case of crash, without breaking with flying debris.

[0075] Using the disclosed technology, a seatback with an optimum weight-to-performance ratio made from natural fibre composites may be designed. The top layer of this composite product 10" can be formed by the composite product 10 of the first embodiment shown in Figure 2 or by the composite product 10 of the second embodiment shown in Figure 3.

[0076] This composite product 10" can also be resistant to UV / visible light and scratches and also can keep the appealing natural fibre appearance when the natural fibres stay visible.BCOMP-11-PCT

Claims

Claims1. Composite product (10; 10'; 10") comprising natural fibres (12) in a matrix, wherein it further comprises an outside protective layer (20) made of a polypropylene based compound (16) comprising:- polypropylene as main component,- organic UV absorbing additive(s), and- light stabilization additive(s) of the family Hindered Amine Light Stabilizers (HALS), notably NOR-HALS,wherein said polypropylene based compound (16) has a Melt Flow Rate (MFR) above 4 g / 10mn , andwherein said polypropylene based compound (16) is transparent or translucent.

2. Composite product (10; 10'; 10") according to claim 1, wherein said matrix comprises a polypropylene based compound (16) comprising:- polypropylene as main component,- organic UV absorbing additive(s), and- light stabilization additive(s) of the family Hindered Amine Light Stabilizers (HALS), notably NOR-HALS,wherein said polypropylene based compound (16) has a Melt Flow Rate (MFR) above 4 g / 10mn, and wherein said polypropylene based compound (16) is transparent or translucent.

3. Composite product (10; 10'; 10") according to claim 1 or 2, wherein the outside protective layer made of said polypropylene based compound (16) has a minimum thickness which is in the range of 5 to 500 pm, preferably between 50 to 200 pm.

4. Composite product (10; 10'; 10") according to any of claims 1 to 3, wherein said polypropylene of said polypropylene based compound (16) is a homopolymer.BCOMP-11-PCT5. Composite product (10; 10'; 10") according to any of claims 1 to 4, wherein said polypropylene of said polypropylene based compound (16) is a random copolymer.

6. Composite product (10; 10'; 10") according to any of claims 1 to 5, wherein said organic UV absorbing additive(s) of said polypropylene based compound (16) comprise(s) organic benzotriazole (BZT).

7. Composite product (10; 10'; 10") according to any of claims 1 to 6, wherein said organic UV absorbing additive(s) of said polypropylene based compound (16) comprise(s) hydroxyphenyl triazine (HPT).

8. Composite product (10; 10'; 10") according to any of claims 1 to 7, wherein said organic UV absorbing additive(s) of said polypropylene based compound (16) comprise(s) cyanoacrylate UV-absorber.

9. Composite product (10; 10'; 10") according to any of claims 1 to 8, wherein said organic UV absorbing additive(s) of said polypropylene based compound comprise(s) hydroxybenzophenone UV-absorber.

10. Composite product (10; 10'; 10") of any of claims 1 to 9, wherein said organic UV absorbing additive(s) of said polypropylene based compound is (are) in the in the range between 0.2% to 5% weight.

11. Composite product (10; 10'; 10") of any of claims 1 to 10 wherein said polypropylene based compound (16) further comprises some inorganic UV-absorbing additive.

72. Composite product (10; 10'; 10") of any of claims 1 to 11, wherein said light stabilization additives comprises High molecular weight Hindered Amine Light Stabilizers (HALS), in particular High molecular weight NOR Hindered Amine Light Stabilizers (HALS).BCOMP-11-PCT13. Composite product (10; 10'; 10") of the preceding claim, wherein said High molecular weight Hindered Amine Light Stabilizers (HALS) is in the range between 0.05% to 2% weight.

14. Composite product (10; 10'; 10") of any of claims 1 to 13, wherein said light stabilization additives comprise Low molecular weight Hindered Amine Light Stabilizers (HALS), in particular Low molecular weight NOR Hindered Amine Light Stabilizers (HALS).

15. Composite product (10; 10'; 10") of the preceding claim, wherein said Low molecular weight Hindered Amine Light Stabilizers HALS are in the range between 0.05 % to 2 % weight.

16. Composite product (10; 10'; 10") of any of claims 1 to 15, wherein said light stabilization additives comprises High molecular weight Hindered Amine Light Stabilizers (HALS) and Low molecular weight Hindered Amine Light Stabilizers (HALS).

17. Composite product (10; 10'; 10") of any of claims 1 to 16, wherein said polypropylene based compound (16) further comprises one or several of the following: antioxidant stabilizer, notably phenolic antioxidant stabilizer, and processing stabilization additive, notably phosphite and / or phosphonite processing stabilizer.

18. Composite product (10; 10'; 10") of any of claims 1 to 17, wherein said polypropylene based compound (16) further comprises one or several adhesion promoter or coupling agent, notably maleic anhydride-modified polypropylene (maPP) and / or glycidyl methacrylate modified polypropylene.

19. Composite product (10; 10'; 10") of any of claims 1 to 18, wherein said polypropylene based compound (16) further comprises one or several of the following : an inorganic scratch improver additive, notably a silicaBCOMP-11-PCTbased inorganic scratch improver additive, and an organic scratch improver additive, notably a silicone based organic scratch improver additive.

20. Composite product (10; 10'; 10") of any of claims 1 to 19, wherein the Melt Flow Rate (MFR) of the polypropylene based compound (16) is between 10 and 200 g / 10 min, preferably between 10 and 30 g / 10 min.

21. Composite product (10; 10'; 10") of any of claims 1 to 20, wherein the Melt Flow Rate (MFR) of the polypropylene based compound (16) is between 30 and 100 g / 10 min.

22. Composite product (10; 10'; 10") of any of claims 1 to 21, wherein the Melt Flow Rate (MFR) of the polypropylene based compound (16) is equal to or above 100 g / 10 min.

23. Composite product (10; 10'; 10") of any of claims 1 to 22, wherein said polypropylene based compound (16) further comprises colouring additive(s) and / or colourant(s), so that said polypropylene based compound (16) is coloured but translucent.

24. Composite product according to any of claims 1 to 23, wherein said natural fibres (12) comprises several stacked layers of natural fibres, wherein said layers of natural fibres form a nonwoven fabric or a woven fabric or a non-oriented natural fibres layer.

25. Composite product (10; 10'; 10") according to any of claims 1 to 24, wherein said natural fibres (12) are made of any of the following fibres or a combination thereof : flax, hemp, sisal, jute, abaca, kenaf, nettle, ramie, henequen, pineapple, banana, and palm or are manmade cellulosic fibres.

26. Composite product (10; 10'; 10") according to any of claims 1 to 25, wherein said natural fibres (12) are protected against UV / visible light damage through a bleaching of the natural fibres and / or through aBCOMP-11-PCTtransparent photo-stabilizer present on the natural fibres, preventing the light induced discoloration, and the photo-oxidation of the lignin, present in the natural fibres.

27. Composite product (10; 10'; 10") according to any of claims 1 to 26, wherein said natural fibres (12) are protected against UV / visible light damage through a colourant of the natural fibres, comprising at least one among organic dyes and organic or inorganic pigments, preventing the light induced discoloration, and the photo-oxidation of the lignin, present in the natural fibres.

28. Composite product (10; 10'; 10") according to any of claims 1 to 27, wherein it further comprises a substrate (30) supporting the natural fibres (12) impregnated by the matrix.

29. Composite product (10; 10'; 10") according to claim 28, wherein said substrate (30) is a composite layer made of a natural fibre woven or nonwoven fabric impregnated with thermoplastic resin, or a polymeric compound.

30. Composite product (10; 10'; 10") according to any of claims 1 to 29, wherein it forms any of the following parts or a portion of any of the following parts : an automobile body part, in particular a car seat, a part of car interior, a car instrument panel, a car console panel, a car door panel, a car armrest, a car headliner, a car interior trim, a car dashboard, a car centre console, a car pillar trim, a car trunk trim, a car roof, a car hood, a car fender, a car spoiler, a car front or rear bumper, a car aerodynamic kit; - a sport article, in particular a canoe, a kayak, a light boat hull, a rod saddle, a bicycle saddle, a bicycle frame, a bicycle handlebar, a baseball bat, a paddle, a ski or walking stick;- an element of furniture or a part of the interior of an airplane, in particular a side panel, a ceiling panel, a luggage compartment; and an aerodynamic part of a light airplane, in particular an engine cowling, a wheel cowling; and an aerodynamic fairing of a mobile machine.BCOMP-11-PCT

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