Part made from natural fibers and polypropylene obtained by injection molding

Abstract

Part based on natural fibers and polypropylene obtained by injection molding The invention relates to an injection molded part comprising (a) at least 15% by weight of a polypropylene selected from a polypropylene homopolymer having a hot melt index of 40 g / 10 min to 80 g / 10 min at 230 °C under a load of 2.16 kg, a polypropylene copolymer having a hot melt index of 1 g / 10 min to 70 g / 10 min at 230 °C under a load of 2.16 kg, and mixtures thereof; (b) from 3 to 25% by weight of natural fibers having an average length of 1 µm to 4 mm; (c) 1 to 5% by weight of a polypropylene copolymer having a hot melt index of 20 g / 10 min to 150 g / 10 min at 230 °C under a 2.16 kg load, and (d) 5 to 60% by weight of an elastomer having a hot melt index of 0.5 g / 10 min to 10 g / 10 min at 190 °C under a 2.16 kg load, and relates to the process of preparing it.Figure for the abbreviation: Figure 1.

Description

Title of the invention: Part based on natural fibers and polypropylene obtained by injection molding FIELD OF THE INVENTION

[0001] The present invention relates to an injection-molded part based on natural fibers, more particularly for the automotive sector. STATE OF THE ART

[0002] Various composite materials useful for the preparation of automotive interior parts are commercially available or described in the literature. For example, application WO 2012 / 093167 describes a composite material comprising:

[0003] (a) from 28 to 95% by weight of a polypropylene-polyethylene copolymer forming a matrix;

[0004] (b) from 0 to 10% by weight of a flow agent, in particular a polyolefin, for example homopolymer of polyethylene or polypropylene;

[0005] (c) from 1 to 20% by weight of an anti-shock agent;

[0006] (d) from 1 to 20% by weight of a compatibilizer; and

[0007] (e) from 3 to 70% by weight of natural fibers,

[0008] and its use in the preparation of interior parts of vehicles.

[0009] Natural fiber composite materials are lighter than those prepared from a glass fiber composite material. However, parts obtained from a natural fiber composite material may be too fragile for use on visible areas.

[0010] We are therefore looking for composite parts based on natural fibers with improved mechanical properties, an improved appearance and a reduced carbon dioxide factor.

[0011] To this end, according to a first object, the invention relates to an injection-molded part, which comprises:

[0012] - (a) at least 15% by weight of a polypropylene chosen from a homopolymer of polypropylene having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and blends thereof,

[0013] (b) from 3 to 25% by weight of natural fibers having an average length of 1 pm to 4 mm,

[0014] (c) from 1 to 5% by weight of a polypropylene copolymer having an index of hot fluidity of 20 g / 10 min to 150 g / 10 min at 230 °C under a load of 2.16 kg, and

[0015] (d) from 5 to 60% by weight of an elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg.

[0016] According to other advantageous aspects of the invention, the injection-molded part comprises one or more of the following features, taken individually or in all technically possible combinations:

[0017] - natural fibers come from miscanthus, flax, hemp shiv, fibers of hemp, reed, oyster, vine shoots, olive stone and a mixture thereof, preferably olive stone, vine shoots, oyster, reed, hemp or shiv fibers, more preferably olive stone, vine shoots or oyster, and even more preferably olive stone;

[0018] - the polypropylene copolymer having a melt flow index of 100 g / 10 min to 150 g / 10 min is grafted, preferably with maleic anhydride;

[0019] - the elastomer is chosen from an ethylene-1-octene elastomer, an elastomer ethylene-1-butene, hydrogenated styrene-isoprene-styrene block copolymers, styrene-ethylene-butylene-styrene and mixtures thereof, and preferably an ethylene-octene elastomer;

[0020] - the injection molded part further comprises (e) from 0 to 1% by weight of additives selected from an antioxidant, a lubricant, a UV light absorber, and mixtures thereof and / or (f) from 0 to 3% by weight of a colorant, a pigment and mixtures thereof; and

[0021] - the injection molded part is an interior trim part visible from a motor vehicle.

[0022] The invention also relates to a method for preparing an injection-molded part comprising injecting into a mold a mixture comprising:

[0023] (a) at least 15% by weight of a polypropylene chosen from a homopolymer of polypropylene having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg and mixtures thereof,

[0024] (b) from 3 to 25% by weight of natural fibers having a length of 1 pm to 4 mm,

[0025] (c) from 1 to 5% by weight of a polypropylene copolymer having an index of hot fluidity of 100 g / 10 min to 150 g / 10 min at 230 °C under a load of 2.16 kg,

[0026] (d) from 5 to 60% by weight of an elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg, and

[0027] whereby the injection molded part is obtained.

[0028] The method may comprise preparing the mixture by extrusion of a composition A comprising components (a), (b), (c), (d) as defined above.

[0029] The method may also comprise:

[0030] i) the extrusion of a composition B comprising:

[0031] (¾) a polypropylene chosen from a polypropylene homopolymer having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and blends thereof, and

[0032] (b) natural fibers having a length of 1 pm to 4 mm,

[0033] in order to obtain a composite material B; and

[0034] ii) the extrusion of a composition C comprising:

[0035] (aü) a polypropylene selected from a polypropylene homopolymer having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and mixtures thereof, and

[0036] (d) an elastomer having a melt flow index of 0.5 g / 10 min at 10 g / 10 min at 230°C under a load of 2.16 kg;

[0037] in order to obtain a composite material C,

[0038] at least one of composition B and composition C further comprising (c) a polypropylene copolymer having a melt flow index of 100 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg,

[0039] iii) mixing composite material B and composite material C in order to obtain the mixture as defined above,

[0040] iv) injecting the mixture into a mold.

[0041] In any of the above embodiments, the mixture may further comprise a colorant, a pigment or mixtures thereof and / or additives. DETAILED DESCRIPTION OF THE INVENTION

[0042] In the present invention, the weight percentages of the constituents of the part are given relative to the total weight of the part.

[0043] In the application, melt flow indices (MFIs) are measured in accordance with ISO 1133-2 (2011).

[0044] The part, as well as the mixture to be injected to form said part, comprises at least 15% by weight, preferably at least 19% by weight, preferably at least 25% by weight, preferably at least 30% by weight, preferably at least 35% by weight, more preferably at least 40% by weight, of a polypropylene chosen from a polypropylene homopolymer having a melt flow index of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer lypropylene having a melt flow index of 1 g / 10 min to 70 g / 10 min, preferably 10 g / min to 70 g / 10 min, at 230°C under a load of 2.16 kg and mixtures thereof.

[0045] The polypropylene homopolymer has a melt flow index at 230°C under a load of 2.16 kg of 40 to 80 g / 10 min, preferably 45 to 70 g / 10 min, more preferably 50 to 60 g / 10 min.

[0046] The polypropylene homopolymer having a melt flow index of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg may comprise recycled polypropylene.

[0047] Preferably, less than 70%, more preferably less than 40%, even more preferably less than 30%, by weight of the polypropylene homopolymer having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg is recycled polypropylene.

[0048] The term "copolymer", as opposed to the term "homopolymer", designates a polymer resulting from the copolymerization of at least two types of monomers, chemically different, called comonomers. The copolymer is therefore formed from at least two repeating units. Depending on the way in which the repeating units are distributed in the macromolecular chains, a distinction is made between copolymers with random, alternating or statistical distribution, and block copolymers. Copolymers resulting from the grafting of pendant groups are also known.

[0049] The polypropylene copolymer is preferably a copolymer of propylene and ethylene.

[0050] The polypropylene copolymer has a melt flow index at 230°C under a load of 2.16 kg of 1 g / 10 min to 70 g / 10 min, preferably 1 to 50 g / 10 min, preferably 1 to 40 g / 10 min, preferably 1 to 30 g / 10 min, especially 1 to 20 g / 10 min, especially 1 to 10 g / 10 min, more preferably 2 g / 10 min to 8 g / 10 min, even more preferably 2 g / 10 min to 6 g / 10 min, even more preferably 2 g / 10 min to 4 g / 10 min, even more preferably about 3 g / 10 min.

[0051] The polypropylene copolymer having a melt flow index of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg may include recycled polypropylene.

[0052] Preferably, less than 70%, more preferably less than 60%, even more preferably less than 50%, by weight of the polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg is recycled polypropylene.

[0053] In the case where the part comprises a mixture of a polypropylene homopolymer and a polypropylene copolymer, the sum of the proportion of the polypropylene homopolymer having a melt flow index of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, and the proportion of the polypropylene copolymer having a melt flow index of 10 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg is at least 30% by weight.

[0054] Preferably, less than 70% by weight, more preferably less than 60% by weight, of the blend of polypropylene homopolymer having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, and polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg is recycled polypropylene.

[0055] The part, as well as the mixture to be injected to form said part, comprises from 3 to 25% by weight, in particular from 5 to 23%, in particular from 10 to 23% by weight, preferably from 17 to 23% by weight, more particularly 20% of natural fibers.

[0056] The term “natural fibers” refers to fibrous materials derived from materials of plant or animal origin. Natural fibers are preferably derived from:

[0057] - of seeds or fruits of a plant, such as olive stone, cotton, kapok, milkweed and / or coconut,

[0058] - from the stem of the plant, such as flax, hemp (hemp shiv or hemp fibers), palm, jute, ramie and / or kenaf,

[0059] - leaves of the plant, such as sisal, Manila hemp, abaca, henequen, raffia and / or agave,

[0060] - from the trunk or branches of the plant, such as vine shoots, wood (resinous or broadleaf) and / or banana tree,

[0061] - herbaceous plants, such as reed, miscanthus, switchgrass, palm, bamboo, sorghum, alfa and / or sabei communis,

[0062] - agricultural stalk waste, such as rice, wheat, coffee grounds and / or corn,

[0063] - of animal hair, secretions or feathers, such as oyster shell, scallop shell Jacques, mussel shell, eggshell, wool, alpaca, mohair, cashmere, angora, goose feathers, silk, Tussah silk or wild silk and / or spider silk,

[0064] and mixtures thereof.

[0065] Natural fibers from miscanthus, flax, hemp shiv, hemp fibers, reed, oyster, vine shoots, olive kernel and mixtures thereof are preferred.

[0066] Natural fibers from olive kernel, for example olive kernel powder, or vine shoots, oyster, in particular oyster shell, and mixtures thereof are more particularly preferred.

[0067] Natural fibers from olive kernels, for example olive kernel powder, are particularly preferred.

[0068] In one embodiment, the natural fibers comprise a mixture of oak and hemp fibers, for example 10 to 20% by weight of hemp fibers. hemp and 5 to 15% by weight of hemp shives relative to the weight of the piece.

[0069] In one embodiment, the natural fibers comprise a mixture of oyster and reed fibers, for example 5 to 15% by weight of oyster fibers and 1 to 10% by weight of reed fibers relative to the weight of the piece.

[0070] In one embodiment, the natural fibers comprise a mixture of fibers derived from olive kernel, for example olive kernel powder, and fibers derived from reed, vine shoots or hemp, for example 15 to 25% by weight of fibers derived from olive kernel and 5 to 15% of fibers derived from hemp, vine shoots or reed relative to the weight of the piece.

[0071] The average length of the natural fibers is between 1 pm and 4 mm, preferably between 1 pm and 2 mm, more preferably between 100 pm and 3 mm, and even more preferably between 500 pm and 2 mm.

[0072] Average length is typically measured by Hi-Res, MorFI or Metso morphology.

[0073] Said fibers are typically obtained by grinding followed by dynamic selection in order to obtain the desired average length.

[0074] Incorporating longer fibers into a composition to be extruded to form the part, and therefore into the part, is generally more difficult to achieve.

[0075] Fiber weight proportions of less than 15% generally lead to a part with insufficient rigidity.

[0076] The presence of natural fibers increases the thermal resistance of the part.

[0077] Even in the presence of these natural fibers, it is possible to obtain large parts, for example such as dashboard inserts, by injection molding. However, optimal injection behavior is observed when the mixture to be injected to form the part contains less than 30% by weight, in particular less than 25% by weight, of natural fibers.

[0078] The part, as well as the mixture to be injected, comprises from 1 to 5% by weight, preferably from 2% to 4% by weight, more preferably 3% by weight of a polypropylene copolymer having a melt flow index of 100 g / 10 min to 150 g / 10 min at 190°C under a load of 2.16 kg, preferably from 110 g / 10 min to 130 g / 10 min, more preferably about 120 g / 10 min.

[0079] The polypropylene copolymer having a melt flow index of 100 g / 10 min to 150 g / 10 min at 190°C under a load of 2.16 kg is advantageously grafted, preferably with a maleic anhydride.

[0080] The polypropylene copolymer acts as a compatibilizing agent, that is to say it ensures good affinity between the fibers and the other components of the mixture to be injected and thus makes it possible to obtain a homogeneous mixture at the injection stage.

[0081] Particularly preferred are polypropylene copolymers grafted with a carboxylic acid (such as maleic acid), one of its esters or anhydrides (such as maleic anhydride), with an epoxy (such as an oxirane, typically a polyolefin obtained using glycidyl methacrylate as a comonomer) and / or a silane.

[0082] The part, as well as the mixture to be injected, further comprises from 5% to 60% by weight, preferably from 8% to 55% by weight, preferably from 8% to 40% by weight, preferably from 15% to 35% by weight, more preferably from 15% to 25% by weight, of an elastomer, the elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg.

[0083] The elastomer is advantageously selected from an ethylene-1-octene elastomer, an ethylene-1-butene elastomer, hydrogenated styrene-isoprene-styrene block copolymers, a styrene-ethylene-butylene-styrene (SEBS) and mixtures thereof, and is preferably an ethylene-1-octene elastomer.

[0084] The elastomer acts as an anti-shock agent. It improves the impact resistance properties of the part. More particularly, the elastomer forms a multi-phase system with the polypropylene matrix, thus improving its resilience.

[0085] Such a proportion of elastomer makes it possible to increase the absorption of impact energy thanks to the plastic deformation of the polymer matrix. Such a high proportion of elastomer compensates for the greater rigidity provided by natural fibers compared to conventional micronized fillers such as talc.

[0086] The elastomer has a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg, preferably of 2 g / 10 min to 5 g / 10 min.

[0087] The low melt flow index of the elastomer is related to the molecular weight of the elastomer and provides impact energy absorption and balanced fluidity for the injection molding process, given the proportion of natural fibers in the composition.

[0088] The part may also comprise less than 20% by weight of a reinforcing mineral filler, in particular talc (Si4Mg3Oio(OH)2), preferably micronized talc.

[0089] The combination of talc and natural fibers makes it possible to balance stiffness and impact resistance according to the requirements of the part. A prior art talc-reinforced PP compound has good impact resistance but does not have high stiffness, whereas the natural fiber-reinforced PP part according to the invention simultaneously has good impact resistance and high stiffness.

[0090] The part may also include a colorant, pigment, or mixtures thereof.

[0091] The part preferably comprises from 0 to 3% by weight of dye, pigment or mixtures thereof.

[0092] The part may also comprise one or more additives, preferably chosen from:

[0093] - an antioxidant, for example a hindered phenol according to the state of the art in combination with hydroxylamine phosphite, for example for heat processing stability, or a thiosynergist in combination with a phenol, particularly where long-term thermal stability is required. The antioxidant is preferably selected from pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and tris(2,4-di(2,4-di-tert-butylphenyl)phosphite and mixtures thereof;

[0094] - a UV stabilizing agent, for example a light stabilizing agent of the type hindered amine (HALS), particularly for inhibiting polymer degradation. Preferably, the UV stabilizing agent is a mixture of high molecular weight HALS comprising a hindered amine 2,2,6,6-tetramethyl-4-piperidinol;

[0095] - a lubricant, such as a release agent;

[0096] - an acid sensor;

[0097] and mixtures thereof.

[0098] Preferably, the total proportion of additives is 0 to 1% by weight.

[0099] In one embodiment, the part consists of:

[0100] (a) at least 40% by weight of a polypropylene selected from a homopolymer of polypropylene having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and blends thereof,

[0101] (b) from 3 to 25% by weight of natural fibers having an average length of 1 pm to 4 mm,

[0102] (c) from 1 to 5% by weight of a polypropylene copolymer having an index of melt flow rate of 100 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg,

[0103] (d) from 5 to 40% by weight of an elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg,

[0104] (e) from 0 to 1% by weight of an additive chosen from an antioxidant, a stabilizing agent UV light, a lubricant, e.g., a release agent, an acid scavenger and mixtures thereof, and

[0105] (f) from 0 to 3% by weight of a dye, a pigment or mixtures thereof.

[0106] In another embodiment, the part consists of:

[0107] (a) at least 15% by weight of a polypropylene chosen from a homopolymer of polypropylene having a melt flow index of 40 g / 10 min to 80 g / 10 min at 230 °C under a load of 2.16 kg, a polypropylene copolymer having a melt flow index of 1 g / 10 min to 70 g / 10 min at 230 °C under a load of 2.16 kg, and mixtures thereof,

[0108] (b) from 3 to 25% by weight of natural fibers having an average length of 1 pm to 4 mm,

[0109] (c) from 1 to 5% by weight of a polypropylene copolymer having an index of melt flow rate of 100 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg,

[0110] (d) from 50 to 60% by weight of an elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg,

[0111] (e) from 0 to 1% by weight of an additive chosen from an antioxidant, a stabilizing agent UV light, a lubricant, e.g., a release agent, an acid scavenger and mixtures thereof, and

[0112] (f) from 0 to 3% by weight of a dye, a pigment or mixtures thereof.

[0113] The part is preferably a vehicle part, preferably a car part, including a visible automotive interior part, for example an interior trim part, such as a dashboard, dashboard insert, center console, glove box, or door panel member, for example a door panel holder or map holder.

[0114] The part may have large dimensions, at least one of the dimensions being greater than 50 cm, preferably greater than 100 cm, sometimes greater than 150 cm. We can cite a dashboard which typically has a dimension of approximately 1600 cm long.

[0115] As the part includes natural fibers, it is more environmentally friendly and generally 6.5 to 7% lighter than a part with an identical composition, except for the replacement of natural fibers with glass fibers.

[0116] The part has improved mechanical properties compared to a part prepared from a composite material based on glass fibers. Thus, it is possible to prepare a part of reduced size, typically of reduced thickness, compared to a part comprising glass fibers while retaining the mechanical properties, in particular rigidity, compared to a part based on glass fibers.

[0117] On this basis, by combining the weight reduction associated with the use of lighter natural fibers and the weight reduction linked to the reduction in the thickness of the part, the part according to the invention is typically 10 to 25% lighter than a part having identical mechanical properties (and therefore thicker) and having an identical composition except for the replacement of the natural fibers by glass fibers.

[0118] Thanks to the synergy between the natural fibers and the ethylene-octene elastomer in the specific proportions of the composition of the part, the part has a better elastic limit (measured according to the ISO 527 standard), and therefore better resistance to impacts, compared to a part without natural fibers and / or ethylene-octene elastomer.

[0119] The ductility of the part, characterized by the elongation at break (measured according to ISO 527) and / or the deformation at maximum strength (measured according to ISO 6603-2), the energy at maximum strength (measured according to ISO 6603-2) and / or the energy at perforation (measured according to ISO 6603-2 and ISO 180 (UN / N-IZOD) is also improved thanks to the synergy between the different components.

[0120] Among the natural fibers, the olive stone, the vine shoots and the oyster, preferably the olive stone or the vine shoots, more preferably the olive stone, make it possible to obtain a particularly satisfactory ductile behavior of the part.

[0121] In addition, the specific composition of the part gives it a so-called "green" appearance. The green appearance allows the user to understand that the part is obtained from environmentally friendly materials. In particular, the natural fibers are uniformly dispersed in the part, but visible at the level of the visible surface of the part.

[0122] In addition, certain natural fibers, in particular fibers from miscanthus or olive kernel, allow the piece to be colored in dark tones as well as in light colors. For example, natural fibers from vine shoots are suitable for light colors and natural fibers from oysters are suitable for coloring the piece in darker tones.

[0123] Thus, the part may be a visible trim of a motor vehicle.

[0124] According to a second object, the invention relates to a method for preparing an injection-molded part comprising injecting into a mold a mixture comprising:

[0125] (a) at least 15% by weight of a polypropylene chosen from a homopolymer of polypropylene having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and blends thereof,

[0126] (b) from 3 to 25% by weight of natural fibers having a length of 1 pm to 4 mm,

[0127] (c) from 1 to 5% by weight of a polypropylene copolymer having an index of hot fluidity of 100 g / 10 min to 150 g / 10 min at 230 °C under a load of 2.16 kg, and

[0128] (d) from 5 to 60% by weight of an elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg,

[0129] whereby an injection molded part is obtained.

[0130] The mixture may also comprise from 0 to 3%, by weight of a colorant, a pigment or mixtures thereof, preferably in a color masterbatch. The color masterbatch typically comprises up to 60% by weight of one or more colorants and a carrier resin, typically a low density polyethylene. Other carrier resins may be used, such as high density polyethylene or polypropylene homopolymer or copolymer.

[0131] The mixture may also comprise one or more additives, preferably chosen from:

[0132] - an antioxidant, for example hindered phenols in combination with hydroxylamine phosphite, particularly for heat processing stability or a thiosynergist in combination with a phenol, particularly where long-term thermal stability is required. The antioxidant is preferably selected from pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and tris(2,4-di(2,4-di-tert-butylphenyl)phosphite and mixtures thereof;

[0133] - a UV stabilizing agent, for example a light stabilizing agent of the type hindered amine (HALS), particularly for inhibiting polymer degradation. Preferably, the UV stabilizing agent is a mixture of high molecular weight HALS comprising a hindered amine 2,2,6,6-tetramethyl-4-piperidinol;

[0134] - a lubricant, such as a release agent;

[0135] - an acid sensor;

[0136] - and mixtures thereof.

[0137] Preferably, the total proportion of additives is 0 to 1% by weight.

[0138] Advantageously, the mixture comprises from 0 to 1% by weight of an additive chosen from an antioxidant, a lubricant, a UV light absorber and mixtures thereof and from 0 to 3% by weight of a dye, a pigment or mixtures thereof.

[0139] The mixture may consist of:

[0140] (a) at least 15% by weight of a polypropylene selected from a homopolymer of polypropylene having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and blends thereof,

[0141] (b) from 3 to 25% by weight of natural fibers having a length of 1 pm to 4 mm;

[0142] (c) from 1 to 5% by weight of a polypropylene copolymer having an index of hot melt flow rate of 100 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg,

[0143] (d) from 5 to 60% by weight of an elastomer, for example an ethylene-octene elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 230°C under a load of 2.16 kg,

[0144] (e) from 0 to 1% by weight of an additive chosen from an antioxidant, a stabilizing agent UV light, a lubricant (such as a release agent), an acid scavenger and mixtures thereof, and

[0145] (f) from 0 to 3% by weight of a dye, a pigment or mixtures thereof, preferably in a color masterbatch.

[0146] According to a first alternative, the method may comprise, before injection, the preparation of the mixture by extrusion of a composition A comprising:

[0147] (a) at least 15% by weight of a polypropylene selected from a homopolymer of polypropylene having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 to 10 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and mixtures thereof,

[0148] (b) from 3 to 25% by weight of natural fibers having a length of 1 pm to 4 mm,

[0149] (c) from 1 to 5% by weight of a polypropylene copolymer having an index of hot fluidity of 100 g / 10 min to 150 g / 10 min at 230 °C under a load of 2.16 kg, and

[0150] (d) from 5 to 60% by weight of an elastomer, for example an ethylene-octene elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 230°C under a load of 2.16 kg,

[0151] in order to obtain the mixture.

[0152] The resulting mixture is therefore in the form of an extruded composition, which is then injected into a mold to form the injection-molded part. Generally, rhomopolymer and / or polypropylene copolymer forms the matrix of the extruded composition.

[0153] The extrusion is preferably carried out in a screw extruder, such as a twin-screw, single-screw or planetary screw extruder, and preferably a co-kneader type single-screw extruder which limits shear and is used at low temperature (< 200°C), which advantageously makes it possible to avoid degradation of the natural fibers and to ensure very good dispersion of the fibers in the polypropylene matrix.

[0154] The extruded composition is typically in the form of pellets, which are used in the next injection molding step.

[0155] Typically, granules of the extruded composition are brought into contact with a heated, temperature-controlled plasticizing screw. The granules are softened under the combined action of the screw and the temperature to reach a viscous state at the front of the screw and constitute the reserve of material ready to be injected. The mixture present at the front of the plasticizing screw is then injected under high pressure into a mold (or cavity) having the desired shape for the part. Then, the part is cooled for a few seconds, before being ejected.

[0156] According to a second alternative, the method may comprise, before the injection,

[0157] i) the extrusion of a composition B comprising:

[0158] (¾) a polypropylene chosen from a polypropylene homopolymer having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and blends thereof,

[0159] (b) natural fibers having a length of 1 pm to 4 mm,

[0160] in order to obtain a composite material B;

[0161] ii) the extrusion of a composition C comprising:

[0162] (aü) a polypropylene selected from a polypropylene homopolymer having a melt flow index of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow index of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and mixtures thereof, and

[0163] (d) an elastomer having a melt flow index of 0.5 g / 10 min at 10 g / 10 min at 230 °C under a load of 2.16 kg,

[0164] in order to obtain a composite material C;

[0165] at least one of composition B and composition C further comprising (c) a polypropylene copolymer having a melt flow index of 100 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg,

[0166] iii) mixing composite material B and composite material C in order to obtain the mixture as defined above,

[0167] iv) injecting the mixture into a mold.

[0168] The extrusion is preferably carried out in a screw extruder, such as a twin-screw, single-screw or planetary screw extruder, and preferably a co-kneader type single-screw extruder which limits shear and is used at low temperature (< 200°C), which advantageously makes it possible to avoid degradation of the natural fibers and to ensure very good dispersion of the fibers in the polypropylene matrix.

[0169] Composite material B is generally extruded in the form of granules, as is composite material C.

[0170] The mixture of composite materials B and C, for example in the form of granules, is typically brought into contact with a heated and temperature-controlled plasticizing screw. The granules are softened under the combined action of the screw and the temperature to reach a viscous state at the front of the screw and constitute the reserve of material ready to be injected, whereby the mixture to be injected is obtained, then injected under high pressure into a mold (or cavity) having the desired shape for the part. The part is then cooled for a few seconds, then ejected.

[0171] The method according to this second alternative generally allows a better dispersion of the natural fibers in the part and a better impact resistance of the part compared to that according to the first alternative.

[0172] The process according to this second alternative generally also makes it possible to mix a wide variety of proportions of composition B and composition C.

[0173] The invention is illustrated by the following examples and figures.

[0174] [Fig-1] [Fig. 1] shows the measured tensile modulus and unnotched Izod for compositions B, C, B80C20, B60C40, B40C60 and B20C80 in Table 3.

[0175] Example 1: Preparation and mechanical properties of the part

[0176] In a twin-screw extruder, six different mixtures were formed by introducing through a first hopper:

[0177] - 2.2 kg of heterophasic polypropylene copolymer (PPC 12642 from Total (Hot melt flow index (2.16 kg at 230°C): 70 g / 10 min);

[0178] - 2 kg of natural fibers of lengths

[0179] O Expi. A (comparative example): no natural fibers;

[0180] O Expi. B: Olive kernel powder <100 pm of BioPowder

[0181] O Expi. C: Fibers from vine shoots (Sarment) < 530 pm from Vitis Valoren

[0182] O Expi. D: Fibers from vine shoots (Sarment) 0 to 4 mm from Vitis Valoren

[0183] O Expi. E: Miscanthus < 500 pm from FRD Lab

[0184] O Expi. F: flax shives 223 pm from the Flax Company

[0185] O Expi. G: 1 mm hemp from APM (Automotive Performance Materials);

[0186] - 5.5 kg of an ethylene-octene copolymer (5.0 g / 10 min, AFFINITI EG 8200 of DOW);

[0187] - 0.3 kg of polypropylene copolymer modified with maleic anhydride (110 g / 10 min, Bondyram 1001CN from Polyram).

[0188] The components and their proportions are indicated in Table 1 below:

[0189] [Tables 1] Component Proportion [wt.%] for exp. B to G Proportion [wt.%] for exp. A Polypropylene heterophasic copolymer MFI = 70 g / 10 min 22% 27.5% Ethylene-octene copolymer 55% 68.75% Maleic anhydride modified polypropylene copolymer 3% 3.75% Natural fibers 20% 0

[0190] Compositions used for the preparation of parts

[0191] The mixture was mixed by extrusion under the following conditions:

[0192] Temperature 180°C

[0193] Pressure: 5 to 30 bars

[0194] The mixture was obtained in the form of granules which were used for the production of samples by injection molding in a Kraus Maffei 130 machine, with a temperature profile of 165 to 185 °C to avoid degradation of the natural fiber and natural fillers.

[0195] The elastic limit of a part obtained by injection molding of each of the six mixtures was measured according to the UNE-EN ISO 527-2 standard.

[0196] The yield strength is higher with natural fibers (exp. B to G) than without natural fibers (comparative exp. A), and at least 16.0 MPa.

[0197] The elongation at break of a part obtained by injection molding of each of the six mixtures was measured according to the UNE-EN ISO 527-2 standard. With the exception of exp. D (vine shoots 0 to 4 mm) and G (hemp shiv), the elongation at break is improved by natural fibers, and greatly improved (14%) for exp. B (natural fibers from olive pit).

[0198] The strain at maximum strength and the perforation strain of a part obtained by injection molding of each of the five composite materials comprising natural fibers were measured according to ISO 6603-2. The highest strain at maximum strength and the highest perforation strain are obtained for expl. A (natural fibers from olive pit).

[0199] The energy at peak strength and puncture energy of a part obtained by injection molding of each of the six composite materials comprising natural fibers were measured according to ISO 6603-2. The highest energy at peak strength and puncture energy are obtained for expl. B (natural fibers from olive kernels).

[0200] The results of the measurements can be seen in Table 2.

[0201] [Tables2] Example ABCDEFG Yield strength (MPa) 15.5 15.9 17.4 17.6 20.0 19.0 18.8 Elongation at break (%) 9.7 14.0 12.0 9.0 11.0 11.0 6.6 Strain at maximum strength (mm) SO 14.0 11.0 9.3 9.3 9.1 7.4 Puncture strain (mm) SO 16.0 12.0 11.0 11.0 10.0 11.0 Energy at maximum strength (J) SO 12.0 6.4 4.7 4.7 4.5 2.7 Puncture energy (J) SO 14.0 7.7 5.8 5.8 5.4 5.1

[0202] Mechanical properties of the parts of examples A to G

[0203] Example 2: impact of the proportion of ethylene-octene elastomer

[0204] In a twin-screw extruder, two different mixtures were produced:

[0205] Composition B:

[0206] - 74% by weight of a nucleated and heterophasic polypropylene copolymer produced in a reactor, presenting a hot melt index of 50 to 60 g / 10 min at 230°C under a load of 2.16 kg, a tensile modulus of 1450 MPa and a notched Izod of 7 kJ / m2;

[0207] - 23% by weight of natural hemp fibers whose particle size is in less than or equal to 4 mm; and

[0208] - 3% by weight of a polypropylene copolymer grafted with a maleic anhydride having a melt flow index of 20 g / 10 min to 50 g / 10 min at 230°C under a load of 2.16 kg.

[0209] The extrusion process was carried out in a Coperion ZSK30 twin-screw extruder, meshing and co-rotating. During the extrusion process, a specific energy of 0.2 kWh / kg was applied for melting and dispersing the natural fibers and fillers in the polypropylene matrix, with a temperature profile not exceeding 180 °C to regulate the melting temperature range of 180 to 190 °C.

[0210] Composition C:

[0211] - 33% by weight of a polypropylene copolymer having a melt flow index of hot 45 to 60 g / 10 min at 230°C under a load of 2.16 kg;

[0212] - 15% by weight of a polypropylene copolymer having a melt flow index of hot from 3 to 5 g / 10 min at 230°C under a load of 2.16 kg;

[0213] - 3% by weight of a polypropylene copolymer having a melt flow index of hot 40 to 50 g / 10 min at 230°C under a load of 2.16 kg;

[0214] - 45% ethylene-1-octene elastomer with a melt flow index of 2 to 3 g / 10 min at 190°C under a load of 2.16 kg;

[0215] - 3% by weight of a high density polypropylene having a melt flow index of hot from 5 to 8 g / 10 min at 190°C under a load of 2.16 kg; and

[0216] - 1% by weight of a combination of antioxidant, lubricant and absorber additives UV light.

[0217] The extrusion process was carried out in a Coperion ZSK30 twin-screw extruder, meshing and co-rotating. During the extrusion process, a specific energy of 0.3 kWh / kg was applied for melting and dispersing the elastomers and polypropylenes in the composition. A temperature profile of 150 to 200 °C was applied to regulate the melting temperature range of 200 to 220 °C.

[0218] Composition B and composition C in pellet form were mixed in four different ratios, prior to injection molding of samples in a Kraus Maffei 130 machine, with a temperature profile of 165 to 185 °C to prevent degradation of natural fibers and natural fillers.

[0219] Samples made from such mixtures of composition B and composition C were tested according to the following test methods:

[0220] Spiral Flow - Determined according to a standard Axxicon ISO spiral mold insert, 4 mm wide and 3 mm thick, mold temperature of 30 °C and injection molding temperature profile of 165 to 185 °C. The injection pressure is 2000 bar and the injection speed is 19 mm / s, injection and cooling time is 26 s, then the total injection cycle is 34 s. The spiral flow dosage of 34 cm3 is derived from the predetermined length of the test material. The spiral flow length is the total length of the solidified material from the injection gate to the end of the flow, as the average of 10 spiral flows molded during a stable injection molding process, having a flow length variation of less than 0.5 mm.Spiral flow determines the flow of molten material until it solidifies in a specified thermodynamic injection molding process, allowing samples to be compared to a reference material.

[0221] The tensile modulus was determined in accordance with ISO R 527.

[0222] Izod impact resistance was determined in accordance with ISO 180 / 1.

[0223] The properties obtained from the mixed compositions B and C are shown in Table 3, with the consequent content in percentage by weight of natural hemp fibers. tutelages from composition B and the percentage by weight of ethylene-octene elastomer from composition C selected in example 2:

[0224] [Tables 3] Example Composition nB (comp.) B80C20 B60C40 B40C60 B20C80 Composition C (comp.) Composition B (wt.%) 100% 80% 60% 40% 20% 0% Composition C (wt.%) 0% 20% 40% 60% 80% 100% Ethylene-Octene (wt.%) 0% 9.0% 18.0% 27.0% 36.0% 45.0% Natural Fiber (wt.%) 23% 18.4% 13.8% 9.2% 4.6% 0% Spiral Flow (cm) 63 65 64 64 61 55 Tensile Modulus (Mpa) 2900 2080 1690 960 780 NA Izod Impact unnotched (kJ / m2) 16.0 Complete fracture 24.0 Hinge fracture 35.0 Partial fracture 51.0 Partial fracture NA No fracture NA No fracture

[0225] In the examples, the blend of compositions B and C comprises polypropylene copolymers having a melt flow index of 2 to 60 g / 10 min at 230°C under a load of 2.16 kg, which gives a broader molecular weight distribution (BMWD) than composition B having a single polypropylene having an MFI of 50 to 60 g / 10 min at 230°C under a load of 2.16 kg.

[0226] Despite the higher MFI of the single polypropylene copolymer of composition B compared to those of composition C, this BMWD is sufficient for injection molding at a temperature below 200°C. This temperature is chosen to avoid degradation of the natural fibers during the transformation process, in contrast to the recommended injection molding temperature range of 230°C ± 30°C for prior art impact-modified polypropylene compounds reinforced with micronized talc.

[0227] Molecular weight, indicated by the melt flow index (MFI), influences melt processability: higher MFI provides longer flow length.

[0228] Furthermore, Example 2 shows that a high molecular weight (BMWD or high polydispersity index) results in a lower melt viscosity. Due to their BMWD, the blend samples B80C20, B60C40 and B40C60 exhibit a spiral flow comparable to that of the reference composition B. The flow length is maintained up to 60% by weight of the composition B dispersed in the composition C.

[0229] The longer flow length of 65 cm exhibited by the B80C20 blend sample compared to the 63 cm flow length of Composition B correlates well with the broader molecular weight distribution of B80C20 compared to Composition C.

[0230] When the ethylene-octene elastomer content of composition C increases to 36% by weight (blend sample B20C80), the flow length decreases to 61 cm. This can be explained by the influence of the higher melt viscosity of composition C, the flow length of which is 55 cm.

[0231] Therefore, the flow length is satisfactory up to 36% by weight of ethylene-octene elastomer in Example 2.

[0232] Furthermore, the tensile modulus of the B60C40 and B40C60 blend samples is suitable for most automotive interior applications, with the B60C40 blend sample being particularly preferred due to its tensile modulus of 1690 MPa.

[0233] This rigidity can be associated with the natural hemp fiber content of 13.8% by weight.

[0234] Generally speaking, [Fig.l] shows a linear correlation between the tensile modulus and the weight percentage of natural fibers in combination with the weight percentage of ethylene-octene elastomer.

[0235] As shown in [Fig.l], a high linear correlation factor (R2 = 0.93) is measured between the tensile modulus and the contents of ethylene-octene elastomer of composition C and natural hemp fibers of composition B. This demonstrates a good dispersion and compatibility of the elastomer phase and natural fibers with the polypropylene matrix, through the injection molding process at a regulated temperature below 200 °C.

[0236] The improvement in impact resistance, represented by the unnotched Izod impact test, is demonstrated by the B60C40 mixture sample, which exhibits a significantly higher value of 35 kJ / m2; compared to the reference value of 16 kJ / m2 of the B mixture sample.

[0237] It is important to note the improvement in the failure mode, which goes from the complete failure, i.e. a brittle failure mode with no plastic deformation, of mixture sample B to partial failure, i.e. plastic deformation with crack formation and propagation, of mixture sample B60C40, due to its high ethylene-octene elastomer content of 18% by weight.

[0238] [Fig. 1] also shows a high linear correlation factor (R2 = 0.97) for the unnotched Izod impact strength values ​​obtained, with the ethylene-octene elastomer content of composition C. This further proves the good dispersion and compatibility of the elastomer phase with the polypropylene matrix, through the injection molding process regulated at a temperature below 200 °C.

[0239] Compared to the B60C40 blend sample, the B40C60 blend sample has an even higher unnotched Izod impact strength of 51 kJ / m2. This may be due to the higher ethylene-octene elastomer content of 27 wt%. The tensile modulus is simultaneously reduced to 960 MPa, probably due to the lower natural hemp fiber content of 9.2 wt% compared to the H60J40 blend sample.

[0240] The B40C60 blend sample is of interest for interior or exterior automotive applications where impact resistance is more important than stiffness.

Claims

Claims

1. An injection-molded part comprising: (a) at least 15 wt% of a polypropylene selected from a polypropylene homopolymer having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and mixtures thereof, (b) 3 to 25 wt% of natural fibers having an average length of 1 μm to 4 mm, (c) 1 to 5 wt% of a polypropylene copolymer having a melt flow rate of 20 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg, and (d) from 5 to 60% by weight of an elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg.

2. An injection molded part according to claim 1, wherein the natural fibers are derived from miscanthus, flax, hemp shiv, hemp fiber, reed, oyster, vine shoots, olive stone and a mixture thereof, preferably olive stone, vine shoots, oyster, reed, hemp or hemp shiv fiber, more preferably olive stone, vine shoots or oyster, and even more preferably olive stone.

3. An injection molded part according to any preceding claim, wherein the polypropylene copolymer having a melt flow rate of 100 g / 10 min to 150 g / 10 min is grafted, preferably with maleic anhydride.

4. An injection molded part according to any preceding claim, wherein the elastomer is selected from an ethylene-1-octene elastomer, an ethylene-1-butene elastomer, hydrogenated styrene-isoprene-styrene block copolymers, a styrene-ethylene-butylene-styrene and mixtures thereof, and preferably an ethylene-octene elastomer.

5. An injection molded part according to any preceding claim further comprising: (e) from 0 to 1% by weight of additives selected from an antioxidant, a lubricant, a UV light absorber, and mixtures thereof and / or (f) from 0 to 3% by weight of a colorant, pigment and mixtures thereof.

6. An injection molded part according to any preceding claim, which is a visible interior trim part of a motor vehicle.

7. A method of preparing an injection-molded part according to any one of claims 1 to 6, comprising injecting into a mold a mixture comprising: (a) at least 15% by weight of a polypropylene selected from a polypropylene homopolymer having a melt flow rate of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg and mixtures thereof, (b) from 3 to 25% by weight of natural fibers having a length of 1 µm to 4 mm, (c) from 1 to 5% by weight of a polypropylene copolymer having a melt flow rate of 100 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg, (d) from 5 to 60% by weight of an elastomer having a melt flow index of 0.5 g / 10 min to 10 g / 10 min at 190°C under a load of 2.16 kg,and by means of which the injection molded part is obtained.,

8. A method according to claim 7, comprising, before injection, preparing the mixture by extrusion of a composition A comprising components (a), (b), (c), (d) as defined according to claim 7.

9. A method according to claim 7 comprising, before injection, i) extruding a composition B comprising: (ai) a polypropylene selected from a polypropylene homopolymer having a melt flow index of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow index of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and mixtures thereof, and (b) natural fibers having a length of 1 μm to 4 mm, in order to obtain a composite material B; and ii) extruding a composition C comprising: (ay) a polypropylene selected from a polypropylene homopolymer having a melt flow index of 40 g / 10 min to 80 g / 10 min at 230°C under a load of 2.16 kg, a polypropylene copolymer having a melt flow rate of 1 g / 10 min to 70 g / 10 min at 230°C under a load of 2.16 kg, and mixtures thereof, and (d) an elastomer having a melt flow rate of 0.5 g / 10 min to 10 g / 10 min at 230°C under a load of 2.16 kg; in order to obtain a composite material C, at least one of composition B and composition C further comprising (c) a polypropylene copolymer having a melt flow rate of 100 g / 10 min to 150 g / 10 min at 230°C under a load of 2.16 kg, iii) mixing composite material B and composite material C in order to obtain the mixture as defined according to claim 7, iv) injecting the mixture into a mold.

10. A method of obtaining an injection molded part according to any one of claims 7 to 9, wherein the mixture further comprises a colorant, a pigment or mixtures thereof and / or additives.

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