Flame-retardant polypropylene composition

Abstract

The invention relates to a flame-retardant polypropylene composition comprising (A) 40-60 wt% of a polypropylene-based polymer, (B) 20-40 wt% of an intumescent halogen free flame retardant, and (C) 11-30 wt% of an uncoated mineral filler with a particle size of 5 µm or more, a process for the preparation of said polypropylene composition, and an article comprising said polypropylene composition.

Description

[0001] FLAME-RETARDANT POLYPROPYLENE COMPOSITION

[0002] The present invention relates to a flame-retardant polypropylene composition, a process for the preparation of said polypropylene composition, and an article comprising said polypropylene composition.

[0003] Polypropylene (PP) is a widely used polymer due to its good processability, physical, mechanical and chemical properties. PP is a very flammable material with a limiting oxygen index (LOI) 17-18% and prone to produce droplets when burning. The application of PP and its compounds is limited for uses where flame retardancy is required, such as electronics, electrical vehicles, building and construction, and appliances.

[0004] Whilst halogenated flame retardants release large amounts of corrosive smoke during burn, halogen free flame retardants are preferred instead as an eco-friendly solution. The modification of PP with addition of flame-retardant materials were disclosed in previous patents, as described in EP3444300B1 where polyolefin-based resin composition containing an intumescent flame retardant based in melamine and piperazine salts delivering good thermal resistance and flame retardancy.

[0005] It is also known in the field to add mineral fillers such as talc to improve mechanical performances of the polypropylene compositions, such as impact strength.

[0006] The general trend in the present field is to use mineral fillers in the form of fine particles with a coating, for example a filler which is treated with a surface modifier such as one or more selected from the group consisting of silanes, amines, glycols, stearates, sorbates and titanates.

[0007] There is still a need in the art for polypropylene compositions further improved in flame retardancy.

[0008] The present invention provides a flame-retardant polypropylene composition comprising:

[0009] (A) 40-60 wt% of a polypropylene-based polymer,

[0010] (B) 20-40 wt% of an intumescent halogen free flame retardant, and

[0011] (C) 11-30 wt% of an uncoated coarse mineral filler with a particle size of 5 pm or more. According to the inventors of the present invention, it was surprisingly found that the use of an uncoated coarse mineral filler allows the good flame retardancy in the composition compared to the use of other talcum.

[0012] The flame-retardant polypropylene composition comprises (A) a polypropylene-based polymer.

[0013] The amount of the component (A) is 40-60 wt%, preferably 45-55 wt%, for example, 48 wt%, 50wt%, or 52 wt%, with respect to the total composition.

[0014] The polypropylene-based polymer may comprise or may be a propylene homopolymer or a propylene copolymer including random copolymers and (multi)block copolymers. Preferably, the polypropylene-based polymer is a propylene homopolymer.

[0015] The copolymer is preferably a random copolymer. The copolymer may consist of at least 70 wt% of propylene monomer units and up to 30 wt% of ethylene and / or a-olefin monomer units, based on the total weight of the copolymer. Preferably, the a-olefin is selected from the group of a-olefins having 4-10 carbon atoms, for example 1 -butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene or 1-octene. The propylene copolymer is preferably a propylene-ethylene copolymer.

[0016] The amount of ethylene and / or a-olefin monomer units in the propylene copolymer is preferably 1-15 wt%, more preferably 1-10 wt%, more preferably 1-6 wt%, more preferably 1-4 wt% based on the total weight of the propylene copolymer.

[0017] When the polypropylene-based polymer comprises a propylene copolymer, the propylene copolymer is preferably a propylene-ethylene random copolymer wherein the amount of ethylene monomer units is 1-15 wt%, more preferably 1-10 wt%, more preferably 1-6 wt%, more preferably 1-4 wt% based on the total weight of the propylene copolymer.

[0018] The MFI of some preferred propylene homopolymer or propylene copolymer may be for example at least 10 dg / min, at least 20 dg / min, at least 30 dg / min or at least 40 dg / min and / or at most 100 dg / min, at most 80 dg / min, at most 60 dg / min or at most 50 dg / min, measured according to ISO1133-1 :2011 (2.16 kg / 230°C). The polypropylene-based polymer may comprise or may be a heterophasic propylene copolymer. Heterophasic propylene copolymers, also known as impact propylene copolymers, are an important class of polymers due to their attractive combination of mechanical properties, such as impact strength over a wide temperature range and their low cost. These copolymers find a wide range of applications ranging from the consumer industry (for example packaging and housewares), the automotive industry to electrical and electronics applications.

[0019] Heterophasic propylene copolymers are generally prepared in one or more reactors, by polymerization of propylene in the presence of a catalyst and subsequent polymerization of an ethylene-a-olefin mixture. The resulting polymeric materials are heterophasic, but the specific morphology usually depends on the preparation method and monomer ratios used.

[0020] The heterophasic propylene copolymers which may be employed in the present invention can be produced using any conventional technique known to the skilled person, for example multistage process polymerization, such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or any combinations thereof. Any conventional catalyst systems, for example, Ziegler-Natta or metallocene may be used. Such techniques and catalysts are described, for example, in W006 / 010414; Polypropylene and other Polyolefins, by Ser van der en, Studies in Polymer Science 7, Elsevier 1990; W006 / 010414, US4399054 and US4472524.

[0021] Preferably, the heterophasic propylene copolymer is made using Ziegler-Natta catalyst.

[0022] The heterophasic propylene copolymer may be prepared by a process comprising:

[0023] - polymerizing propylene and optionally ethylene and / or a-olefin in the presence of a catalyst system to obtain the propylene-based matrix and

[0024] - subsequently polymerizing ethylene and a-olefin in the propylene-based matrix in the presence of a catalyst system to obtain the dispersed ethylene-a olefin copolymer. These steps are preferably performed in different reactors. The catalyst systems for the first step and for the second step may be different or same.

[0025] The heterophasic propylene copolymer of the composition of the invention consists of a propylene-based matrix and a dispersed ethylene-a-olefin copolymer. The propylene- based matrix typically forms the continuous phase in the heterophasic propylene copolymer. The amounts of the propylene-based matrix and the dispersed ethylene-a- olefin copolymer may be determined by13C-NMR, as well known in the art. The propylene-based polymer may be one type of heterophasic propylene copolymer or a mixture of different types of heterophasic propylene copolymers, e.g., a mixture of a first type of a heterophasic propylene copolymer and a second type of heterophasic propylene copolymer at any weight ratio, e.g., 1 :99-99:1 or 50:50.

[0026] The heterophasic propylene copolymer consists of

[0027] (a) a propylene-based matrix, wherein the propylene-based matrix consists of a propylene homopolymer and / or a propylene copolymer consisting of at least 70 wt% of propylene monomer units and at most 30 wt% of ethylene and / or a-olefin monomer units, based on the total weight of the propylene-based matrix and wherein the propylene-based matrix is present in an amount of 60 to 95 wt% based on the total heterophasic propylene copolymer and

[0028] (b) a dispersed ethylene-a-olefin copolymer, wherein the dispersed ethylene-a-olefin copolymer is present in an amount of 40 to 5 wt% based on the total heterophasic propylene copolymer and wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-a-olefin copolymer in the heterophasic propylene copolymer is 100 wt% with respect to the heterophasic propylene copolymer.

[0029] The propylene-based matrix consists of a propylene homopolymer and / or a propylenecopolymer consisting of at least 70 wt% of propylene monomer units and up to 30 wt% of ethylene and / or a-olefin monomer units, for example consisting of at least 80 wt% of propylene monomer units and up to 20 wt% of ethylene and / or a-olefin monomer units, for example consisting of at least 90 wt% of propylene monomer units and up to 10 wt% of ethylene and / or a-olefin monomer units, based on the total weight of the propylene-based matrix. Preferably, the a-olefin is selected from the group of a-olefins having 4 to 10 carbon atoms, for example 1-butene, 1-pentene, 4-methyl-1-pentene, 1- hexene, 1 -heptene or 1 -octene. The propylene copolymer is preferably a propyleneethylene copolymer.

[0030] Preferably, the propylene-based matrix consists of a propylene homopolymer. When the propylene-based matrix consists of a propylene homopolymer, a higher stiffness is obtained compared to the case where the propylene-based matrix is a propylene copolymer as described above, which may be advantageous. The melt flow index (MFI) of the propylene-based matrix (before the heterophasic propylene copolymer is mixed into the composition of the invention), MFIPP. may be for example at least 0.1 dg / min, at least 0.2 dg / min, at least 0.3 dg / min, at least 0.5 dg / min, at least 1 dg / min, at least 1 .5 dg / min, and / or for example at most 50 dg / min, at most 40 dg / min, at most 30 dg / min, at most 25 dg / min, at most 20 dg / min, measured according to ISO1133 (2.16 kg / 230°C). The MFIPPmay be in the range of for example 0.1 to 50 dg / min, for example from 0.2 to 40 dg / min, for example 0.3 to 30 dg / min, for example 0.5 to 25 dg / min, for example from 1 to 20 dg / min, for example from 1.5 to 10 dg / min, measured according to ISO1133 (2.16 kg / 230°C).

[0031] The propylene-based matrix is present in an amount of 60 to 95wt%. Preferably, the propylene-based matrix is present in an amount of 60 to 80wt%, for example at least 65 wt% or at least 70 wt% and / or at most 78 wt%, based on the total heterophasic propylene copolymer.

[0032] The propylene-based matrix is preferably semi-crystalline, that is it is not 100% amorphous, nor is it 100% crystalline. For example, the propylene-based matrix is at least 40% crystalline, for example at least 50%, for example at least 60% crystalline and / or for example at most 80% crystalline, for example at most 70% crystalline. For example, the propylene-based matrix has a crystallinity of 60 to 70%. For purpose of the invention, the degree of crystallinity of the propylene-based matrix is measured using differential scanning calorimetry (DSC) according to ISO11357-1 and ISO11357- 3 of 1997, using a scan rate of 10°C / min, a sample of 5mg and the second heating curve using as a theoretical standard for a 100% crystalline material 207.1 J / g.

[0033] Besides the propylene-based matrix, the heterophasic propylene copolymer also comprises a dispersed ethylene-a-olefin copolymer. The dispersed ethylene-a-olefin copolymer is also referred to herein as the ‘dispersed phase’. The dispersed phase is embedded in the heterophasic propylene copolymer in a discontinuous form. The particle size of the dispersed phase is typically in the range of 0.05 to 2.0 microns, as may be determined by transmission electron microscopy (TEM). The amount of the dispersed ethylene-a-olefin copolymer in the heterophasic propylene copolymer may herein be sometimes referred as RC.

[0034] In some preferred heterophasic propylene copolymers, the amount of ethylene monomer units in the ethylene-a-olefin copolymer is in the range of 5 to 65 wt%, for example at most 40 wt%, at most 30 wt% or at most 20 wt%, based on the total weight of the ethylene-a-olefin copolymer. The amount of ethylene in the dispersed ethylene- a-olefin copolymer in the heterophasic propylene copolymer may herein be sometimes referred as RCC2.

[0035] The a-olefin in the ethylene-a-olefin copolymer is preferably chosen from the group of a-olefins having 3 to 8 carbon atoms. Examples of suitable a-olefins having 3 to 8 carbon atoms include but are not limited to propylene, 1 -butene, 1 -pentene, 4-methyl- 1 -pentene, 1 -hexene, 1 -heptene and 1 -octene. More preferably, the a-olefin in the ethylene-a-olefin copolymer is chosen from the group of a-olefins having 3 to 4 carbon atoms and any mixture thereof, more preferably the a-olefin is propylene, in which case the ethylene-a-olefin copolymer is ethylene-propylene copolymer.

[0036] The MFI of the dispersed ethylene a-olefin copolymer (before the heterophasic propylene copolymer is mixed into the composition of the invention), MFIEPR, may be for example at least 0.001 dg / min, at least 0.01 dg / min, at least 0.1 dg / min, at least 0.3 dg / min, at least 0.7 dg / min, at least 1 dg / min, and / or for example at most 30 dg / min, at most 20 dg / min, at most 15 dg / min at most 10 dg / min, at most 5 dg / min or at most 3 dg / min. The MFIEPR may be in the range for example from 0.001 to 30 dg / min, for example from 0.01 to 20 dg / min, for example 0.1 to 15 dg / min, for example 0.3 to 10 dg / min, for example from 0.7 to 5 dg / min, for example from 1 to 3 dg / min. MFIEPR is calculated taking into account the MFI of the propylene-based matrix (MFIPP) measured according to ISO1133 (2.16 kg / 230 °C), the MFI of the heterophasic propylene copolymer (MFIheterophasic) measured according to ISO1133 (2.16 kg / 230 °C) and the amount of the propylene-based matrix in the heterophasic propylene copolymer (matrix content) and the amount of the dispersed phase in the heterophasic propylene copolymer (rubber content (RC)) according to the following formula:

[0037] The dispersed ethylene-a-olefin copolymer is present in an amount of 40 to 5 wt% based on the total heterophasic propylene copolymer. In some preferred heterophasic propylene copolymers, the dispersed ethylene-a-olefin copolymer is present in an amount of at least 10 wt%, for example at least 15 wt% or at least 17 wt%, and / or at most 35 wt%, for example at most 30 wt% or 25 wt%, based on the total heterophasic propylene copolymer.

[0038] In the heterophasic propylene copolymer in the composition of the invention, the sum of the total weight of the propylene-based matrix and the total weight of the dispersed ethylene-a-olefin copolymer is 100 wt% with respect to the heterophasic propylene copolymer. Preferably, the heterophasic propylene copolymer has a fraction soluble in p-xylene at 25 °C (CXS) measured according to ISO 16152:2005 of 40 to 5 wt%. In some preferred heterophasic propylene copolymers, the heterophasic propylene copolymer has CXS of at least 10 wt%, for example at least 15 wt% or at least 17 wt%, and / or at most 35 wt%, for example at most 30 wt% or 25 wt%. In some preferred heterophasic propylene copolymers, the heterophasic propylene copolymer has CXS of 10 to 25 wt%. In some preferred heterophasic propylene copolymers, the heterophasic propylene copolymer has CXS of 25 to 40 wt%.

[0039] Preferably, the amount of ethylene monomer units in the heterophasic propylene copolymer (sometimes referred as TC2) is in the range of 3-25 wt% based on the heterophasic propylene copolymer. For example, the amount of ethylene monomer units in the heterophasic propylene copolymer may be at least 5 wt% or at least 7 wt% and / or at most 20 wt%, at most 15 wt% or at most 13 wt%, based on the heterophasic propylene copolymer.

[0040] The MFI of some preferred heterophasic propylene copolymers may be for example at least 10 dg / min or at least 15 dg / min and / or at most 50 dg / min or at most 40 dg / min, measured according to ISO1133 (2.16 kg / 230°C). The MFI of some preferred heterophasic propylene copolymers may be for example at least 0.1 dg / min, at least 0.2 dg / min, at least 0.3 dg / min, at least 0.5 dg / min, at least 1 dg / min at least 1.5 dg / min, and / or for example at most 8 dg / min or at most 5 dg / min, measured according to ISO1133 (2.16 kg / 230°C).

[0041] The values of the MFI of the propylene-based matrix (MFIPP) and the MFI of the dispersed ethylene-a-olefin elastomer (MFIEPR) mentioned herein are understood as the values before the heterophasic propylene copolymer is mixed with other components to obtain the composition according to the invention. The value of the MFI of the heterophasic propylene copolymer (MFIheterophasic) refers to the final MFI of the heterophasic propylene copolymer. To exemplify this:

[0042] In case the heterophasic propylene copolymer is not subjected to vis-breaking or shifting by melt-mixing with a peroxide, the MFIheterophasic is the original MFI value of the heterophasic propylene copolymer. In case the heterophasic propylene copolymer is subjected to vis-breaking or shifting by melt-mixing with a peroxide, the MFIheterophasic is the value of the heterophasic propylene copolymer after such visbreaking or shifting.

[0043] Preferably, in the heterophasic propylene copolymer according to the invention, the propylene copolymer of the matrix consists of propylene monomer units and ethylene and / or a-olefin monomer units wherein the a-olefin is selected from the group of a-olefins having 2 or 4 to 10 carbon atoms and the dispersed ethylene-a-olefin copolymer consists of ethylene and a-olefin selected from the group of a-olefins having 3 to 8 carbon atoms.

[0044] The propylene-based polymer may also be a combination of any of the propylene- based polymer mentioned above, e.g. a mixture of a propylene homopolymer and a heterophasic propylene copolymer at a weight ratio of 1 :99-99:1 or 50:50, a mixture of a propylene homopolymer and a random propylene-ethylene copolymer at a weight ratio of 1 :99-99:1 or 50:50 or a mixture of two different types of propylene homopolymer at a weight ratio of 1 :99-99:1 or 50:50.

[0045] (B) Flame retardant

[0046] The flame-retardant polypropylene composition comprises (B) a flame retardant, which is an intumescent halogen free flame retardant.

[0047] The amount of the component (B) is 20-40 wt%, preferably 25-35 wt%, for example, 28 wt%, 30wt%, or 32 wt%, with respect to the total composition.

[0048] The intumescent halogen free flame retardant comprises at least one non-halogen flame retardant compound. Examples of the non-halogen flame retardant compound include ammonium phosphate, ammonium polyphosphate; melamine orthophosphate, melamine pyrophosphate, melamine polyphosphate, and melamine phosphate; piperazine orthophosphate, piperazine phosphate, piperazine polyphosphate, and piperazine pyrophosphate.

[0049] Further examples of the non-halogen flame retardant compound include phosphinates of the following phosphinic acids: dimethylphosphinic acid, ethylmethylphosphinic acid, diethylphosphinic acid, methyl-n-propylphosphinic acid, methanedi(methylphosphinic acid), benzene-1 ,4-(dimethylphosphinic acid), methylphenylphosphinic acid and diphenylphosphinic acid. Examples also include metal salts of the above dialkyl or diaryl or arylalkyl phosphinic acid, where metal is an alkali metal, Li, Na, K and Cs and the like or alkaline earth metal, Be, Ca, Mg, Ba, Sr and the like or a transition metal, Zn, Ti and the like or other main group elements such as Al, Sn, Sb and the like, such as aluminum diethyl phosphinate.

[0050] In one embodiment, the non-halogen flame retardant comprises a melamine polyphosphate and an aluminum diethyl phosphinate. In an embodiment, the non- halogen flame retardant agent consists of a melamine polyphosphate and an aluminum diethyl phosphinate in a weight ratio of 0.5-2, such as 1.

[0051] In one embodiment, the non-halogen flame retardant comprises an organic phosphate compound, an organic phosphoric acid compound and zinc oxide. Preferably, the weight ratio of organic phosphate compound to organic phosphoric acid compound is 1 :0.01 to 1 :2, more preferably, the weight ratio is from 2:1 to 1 :1. The organic phosphate compound is selected from the group consisting of piperazine pyrophosphate, piperazine polyphosphate, piperazine phosphate or combinations thereof. The organic phosphoric acid compound is selected from the group consisting of melamine pyrophosphate, melamine polyphosphates, melamine phosphate or combinations thereof. It is preferred that the phosphoric acid compound is melamine phosphate.

[0052] The zinc oxide is used in an amount of from 2 - 10 wt.%, more preferably from 3 - 6 wt.% based on the weight of the flame retardant.

[0053] A similar flame retardant is described in WO2016102278A1.

[0054] In one embodiment, the flame retardant is a nitrogen-phosphorus based flame retardant, preferably comprising or consisting of 60-70 wt% of a piperazine pyrophosphate, 25-35 wt% of a melamine phosphate compound and 2-8 wt% of ZnO.

[0055] (C) Mineral filler

[0056] The flame-retardant polypropylene composition comprises (C) a mineral filler. The mineral filler is not coated and / or is coarse. The mineral filler has a particle size of 5 pm or more.

[0057] The amount of the component (C) is 11-30 wt%, preferably 15-25 wt%, for example, 18 wt%, 20wt%, or 22 wt%, with respect to the total composition.

[0058] Examples of the mineral filler include talc, calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, magnesium hydroxide, magnesium oxide, aluminium hydroxide, magnesium sulphate, barium sulphate, glass powder, clay, dolomite, mica, silica, alumina, potassium titanate, wollastonite, and fibrous magnesium oxysulphate. These inorganic fillers may be used alone or in any combination of two or more thereof. Talc, calcium carbonate, clay and dolomite are particularly preferred as inorganic filler.

[0059] In one embodiment, the composition of the invention comprises talc. Talc can be categorised as a hydrated magnesium silicate and its main components can be represented by, amongst others, one or more of the formulas (Si2O5)2Mg3(OH)2, SisMg602o(OH)4 or Mgi2Sii604o(OH)s.

[0060] In one embodiment, the composition of the invention comprises calcium carbonate.

[0061] In one embodiment, the composition does not comprise other fillers than component

[0062] (C). In one embodiment, the composition does not comprise other fillers than talc and calcium carbonate.

[0063] The mineral filler used in the present invention is not a surface-treated filler or surface-coated filler, for example a filler which is treated with a surface modifier such as one or more selected from the group consisting of silanes, amines, glycols, stearates, sorbates and titanates.

[0064] The mean particle size of the mineral filler (D50) is preferably in the range of 5-30 pm, preferably in the range of 5-20 pm, more preferably in the range of 10-15 pm, according to sedimentation analysis, Stokes’ law (ISO 13317-3).

[0065] The BET specific surface area of the mineral filler is preferably in the range of 7m2 / g or less, preferably in the range of 1-6 m2 / g, more preferably in the range of 2-5 m2 / g, according to ISO 9277.

[0066] (D) Additives

[0067] Optionally, the flame-retardant polypropylene composition comprises (D) additives.

[0068] The amount of the component (D) is 0-5 wt%, preferably 0.01-5 wt%, more preferably 0.1-2wt%, for example, 0.5 wt%, 0.8wt%, 1.0 wt%, or 1.5 wt%, with respect to the total composition.

[0069] The additives may include nucleating agents, stabilizers, e.g., heat stabilizers, antioxidants, UV stabilizers; colorants, like pigments and dyes; clarifiers; surface tension modifiers; lubricants; mould-release agents; flow improving agents; plasticizers; anti-static agents and blowing agents.

[0070] The sum of all components added in the process of the invention to form the composition comprising (A), (B), (C) and the optional component (D) should add up to 100% by weight of the total composition. In one embodiment, a total amount of components (A)-(B) is at least 60wt%, preferably at least 70 wt%, more preferably at least 75wt%, and at most 85 wt%, preferably at most 82 wt%, more preferably at most 80 wt%.

[0071] In one embodiment, a total amount of components (A)-(C) is at least 95wt%, preferably at least 98 wt%, more preferably at least 99wt%, even more preferably at least 99.9wt%.

[0072] A total amount of components (A)-(D) is at least 95wt%, preferably at least 99 wt%, more preferably at least 99.9 wt%, even more preferably 100 wt%.

[0073] In one embodiment, the composition has a flame retardancy of VO according to the UL94 test standard at a sample thickness of 1.6 mm.

[0074] In one embodiment, the composition has a flame retardancy of VO according to the UL94 test standard at a sample thickness of 2.0 mm.

[0075] In one embodiment, the composition has a warpage of 1 .0% or less according to ISO 294-4.

[0076] Process for making the composition

[0077] The composition of the invention may be obtained by a process comprising melt-mixing (A), (B), (C) and optionally (D) by using any suitable means. Accordingly, the invention further relates to a process for the preparation of the composition according to the invention comprising melt mixing (A), (B), (C) and optionally (D). Preferably, the composition of the invention is made in a form that allows easy processing into a shaped article in a subsequent step, like in pellet or granular form. Preferably, the composition of the invention is in pellet or granular form as obtained by mixing all components in an apparatus like an extruder; the advantage being a composition with homogeneous and well-defined concentrations of the additives.

[0078] With melt-mixing, it is meant that the components (B) and (C) and optionally (D) are mixed with (A) at a temperature that exceeds the melting point of the component (A). Melt-mixing may be done using techniques known to the skilled person, for example in an extruder. Generally, in the process of the invention, melt-mixing is performed at a temperature in the range from 170-300°C.

[0079] Suitable conditions for melt-mixing, such as temperature, pressure, amount of shear, screw speed and screw design when an extruder is used are known to the skilled person. When using an extruder, a conventional extruder such as a twin-screw extruder may be used. The temperature can vary through the different zones of the extruder as required. For example, the temperature may vary from 100°C in the feed zone to 300°C at the die. Preferably, the temperature in the extruder varies from 200 to 265°C. Likewise, the screw speed of the extruder may be varied as needed. Typical screw speed is in the range from about 100rpm to about 400rpm.

[0080] Further aspects

[0081] The composition according to the invention may be processed by any conventional technique known in the art into an article. Suitable examples of processing techniques wherein the composition according to the invention may be used include: injection moulding, injection blow moulding, injection stretch blow moulding, rotational moulding, compression moulding, extrusion, extrusion compression moulding, extrusion blow moulding, sheet extrusion, film extrusion, cast film extrusion, foam extrusion, thermoforming and thin-walled injection moulding.

[0082] The invention further relates to an article comprising the composition according to the invention. In particular, the invention relates to an article comprising the composition according to the invention, wherein the article is made by one of the processing techniques mentioned above.

[0083] Preferably, the article according to the invention is used in electrical vehicles and electronic appliances, such as battery components for electric vehicles, charging station components, power tools, household goods and appliances parts such as cooktops, refrigerators, and washer boiler covers.

[0084] The invention further relates to the use of the composition according to the invention for electrical and electronic appliances.

[0085] It is noted that the invention relates to all possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein.

[0086] It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product / composition comprising certain components also discloses a product / composition consisting of these components. The product / composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product / composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process.

[0087] When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

[0088] The invention is now elucidated by way of the following examples, without however being limited thereto.

[0089] Examples

[0090] Materials as shown in Table 1 were used in the experiments.

[0091] Table 1

[0092] The components of the compositions as shown in Table 2 were melt-mixed by a twin- screw extruder to obtain pellets, which were molded into test samples. Various properties were measured on the samples. The flame retardancy was measured according to the UL94 test standard, wherein the sample was conditioned at 23 °C ±2 °C and 50 percent ± 10% relative humidity for 48 hours prior to testing.

[0093] According to the UL94 standard, VO indicates the best flammability behaviour, followed by ratings V1 , V2 and NR (no rating). Although good V-0 performance could be reached by all the examples 1-7 at 3mm sample thickness, when the sample thickness is decreased to 1.6mm (the thinner the harder to pass the flame retardancy test), only inventive examples 1 and 7 using an uncoated coarse talc formulation show V-0 flammability performance.

[0094] As indicated in example 1 , the polypropylene composition using a coarse talc delivers also exceptional LOI (limiting oxygen index) as measured according to ASTM D2863. Also, the polypropylene composition of example 7 using an uncoated coarse talc formulation shows a warpage (ISO 294-4) of 0.8%, meeting industrial needs for low warpage on determined E&E (electric and electronic) applications. Known warpage for commercial short glass fiber filled polypropylene flame-retardant compounds (SABIC H1015 and SABIC H1030) are obviously higher, particularly between 1.7-2%.

[0095] Table 2 (amounts in weight parts)

[0096] The components of the compositions as shown in Table 3 were melt-mixed by a twin- screw extruder to obtain pellets, which were molded into test samples. Various properties were measured on the samples.

[0097] As indicated, the inventive example 10, which uses an uncoated coarse CaCO3as the mineral filler, achieved V-0 flammability performance at 2 and 3mm sample thicknesses, whilst the other calcium carbonate used in comparative examples 8-9 could not reach a flammability result (no rating - NR).

[0098] As such, the same principle as seen for talc applies for calcium carbonate, where uncoated coarse mineral fillers showed good flammability performance whereas other types of conventional mineral fillers (finer particle size and / or coating) show an antagonistic effect with the flame retardant agent. Table 3 (amounts in weight parts)

Claims

CLAIMS1 . A flame-retardant polypropylene composition, relative to the total weight thereof, comprising:(A) 40-60 wt% of a polypropylene-based polymer,(B) 20-40 wt% of an intumescent halogen free flame retardant, and(C) 11-30 wt% of an uncoated coarse mineral filler selected from the group consisting of talc and calcium carbonate with a particle size of 5 pm or more, wherein the flame retardant comprises 60-70 wt% of a piperazine pyrophosphate, 25-35 wt% of a melamine phosphate compound and 2-8 wt% of ZnO based on the total weight of the flame retardant, and wherein the composition does not comprise other fillers than component (C).

2. The composition according to claim 1 , further comprising:(D) 0.01-5 wt% of additives.

3. The composition according to any one of the preceding claims, wherein a total amount of components (A)-(C) is at least 95wt%, preferably at least 98 wt%, more preferably at least 99wt%, even more preferably at least 99.9wt%.

4. The composition according to any one of the preceding claims, wherein the amount of component (A) is 45-55 wt%.

5. The composition according to any one of the preceding claims, wherein the amount of component (B) is 25-35 wt%.

6. The composition according to any one of the preceding claims, wherein the amount of component (C) is 15-25 wt%.

7. The composition according to any one of the preceding claims, wherein the amount of component (D) is 0.1 -2.0 wt%, and the additives comprises one or more selected from the group consisting of nucleating agents, heat stabilizers, antioxidants, UV stabilizers, colorants, clarifiers, surface tension modifiers, lubricants, mould-release agents, flow improving agents, plasticizers, anti-static agents and blowing agents.

8. The composition according to any one of the preceding claims, wherein the component (C) has a particle size in the range of 5-30 pm, preferably in the range of 5-20 pm, more preferably in the range of 10-15 pm.

9. The composition according to any one of the preceding claims, wherein the component (C) has a superficial area of 7m2 / g or less, preferably in the range of 1-6 m2 / g, more preferably in the range of 2-5 m2 / g.

10. The composition according to any one of the preceding claims, wherein (A) the polypropylene-based polymer is a propylene homopolymer or a propylenecopolymer consisting of at least 70 wt% of propylene monomer units and at most 30 wt% of ethylene and / or a-olefin monomer units based on the copolymer.

11. The composition according to any one of the preceding claims, wherein the polypropylene-based polymer (A) has a MFI of 10 to 100 dg / min, preferably 20 to 80 dg / min, measured according to ISO1133-1 :2011 at 2.16 kg and 230°C.

12. The composition according to any one of the preceding claims, wherein the composition has a flame retardancy of V0 according to the UL94 test standard at a sample thickness of 1.6 mm, and / or the composition has a flame retardancy of V0 according to the UL94 test standard at a sample thickness of 2.0 mm.

13. The composition according to any one of the preceding claims, wherein the composition has a warpage of 1 .0% or less according to ISO 294-4.

14. A process for the preparation of the composition according to any one of the preceding claims, comprising melt mixing (A), (B), and (C) and optional components.

15. An article comprising the composition according to any one of claims 1-13, preferably wherein the article is used in electrical vehicles and electronic appliances.

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