Polypropylene composition

Abstract

The present invention relates to a polypropylene composition, a method for preparing the same, and an article comprising such a polyolefin composition. The polypropylene composition comprises (A) a heterophasic polypropylene, (B) optionally a first elastomer of ethylene and α-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev of 0-3%, (C) optionally a second elastomer of ethylene and α-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev of above 3%, and (D) optionally a block copolymer comprising a terminal block comprising styrene or alpha-methyl styrene, wherein a sum of (B), (C) and (D) is in the range of 10-30 wt% of the polypropylene composition, and the amount of (C) is less than 60 wt% of the sum of (B), (C) and (D).

Description

[0001] POLYPROPYLENE COMPOSITION

[0002] The present invention relates to a polypropylene composition, a method for preparing the same, and an article comprising such a polyolefin composition.

[0003] Polypropylene is a versatile thermoplastic material known for its excellent chemical resistance, high melting point, and good strength-to-weight ratio. It has been widely used in various applications, such as packaging, textiles, and automotive components. It is widely known in the art to add a polyolefin elastomer to the base polypropylene to improve its impact strength, flexibility, thermal resistance, and adhesion properties, making it more versatile and suitable for a wider range of applications.

[0004] However, the addition of the polyolefin elastomer has the disadvantage of deteriorating other properties such as transparency. For applications in need of a transparent appearance of the articles produced from such polypropylene compositions, a balance between mechanical properties and optical properties needs to be improved.

[0005] Heterophasic polypropylene (PP) is known for its enhanced impact resistance in comparison with other types of polypropylenes, including homophasic PP. However, heterophasic PP tends to be less transparent than homophasic PP, because homophasic PP has a more uniform crystal structure, which allows it to transmit light more evenly and appear more transparent. Heterophasic PP, on the other hand, normally has a mixture of ethylene-propylene rubber phase and a homo propylene matrix phase, which can scatter light and reduce transparency. For applications in need of a transparent appearance, heterophasic PP is usually not a choice. W02019043087A1 discloses a polypropylene composition for use as a storage container, which requires transparency. Heterophasic PP is specifically excluded from the choice for the polypropylene.

[0006] It has been unexpectedly discovered by the inventors of the present invention that heterophasic polypropylene can be used in applications in need of transparency by way of addition of specific types of polyolefin elastomers or polystyrene block copolymers. In fact, the transparency of the polypropylene composition is unexpectedly increased after addition of such components, contrary to common understandings in the field. In one aspect, the present invention provides a polypropylene composition comprising:

[0007] (A) a heterophasic polypropylene consisting of 60-98 wt% of a propylene-based matrix and 2-40 wt% of a dispersed ethylene-a-olefin copolymer, wherein the propylene-based matrix consists of a propylene homopolymer and / or a propylene copolymer consisting of at least 90 wt% of propylene monomer units and at most 10 wt% of comonomer units selected from ethylene monomer units and a-olefin monomer units having 4 to 10 carbon atoms, wherein the amount of ethylene monomer units in the ethylene-a-olefin copolymer is 10 to 60 wt%, and the a-olefin in the ethylene-a-olefin copolymer is chosen from the group of a-olefins having 3 to 8 carbon atoms, and at least one of (B), (C) and (D),

[0008] (B) a first elastomer of ethylene and a-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev of 0-3%,

[0009] Dev = [(density of polypropylene)-(density of elastomer) ] / (density of polypropylene)*100%,

[0010] (C) a second elastomer of ethylene and a-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev of above 3%,

[0011] (D) a block copolymer comprising a terminal block comprising styrene or alpha-methyl styrene, wherein a sum of (B), (C) and (D) is in the range of 10-30 wt% of the polypropylene composition, and the amount of (C) is less than 60 wt% of the sum of (B), (C) and (D).

[0012] The polypropylene composition of the present invention optionally comprises:

[0013] (E) 0-10 wt% of a filler.

[0014] The polypropylene composition of the present invention optionally comprises:

[0015] (F) 0-10 wt% of additives.

[0016] The polypropylene composition of the present invention unexpectedly achieves an improved transparency in comparison with the heterophasic polypropylene used in the composition and achieves an improved balance between impact strength and transparency.

[0017] (A) Heterophasic polypropylene

[0018] The composition according to the invention comprises a heterophasic polypropylene (A). Heterophasic polypropylenes, or 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.

[0019] The heterophasic propylene copolymers 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 Ven, Studies in Polymer Science 7, Elsevier 1990; W006 / 010414; US4399054 and US4472524.

[0020] Preferably, the heterophasic propylene copolymer is made using Ziegler-Natta catalyst.

[0021] The heterophasic propylene copolymer may be prepared by a process comprising:

[0022] - polymerizing propylene and optionally ethylene and / or a-olefin in the presence of a catalyst system to obtain the propylene-based matrix and

[0023] - 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.

[0024] 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 comprises a propylene-based matrix and a dispersed ethylene-a-olefin copolymer, which are certainly different from each other. 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 matrix consists of a propylene homopolymer and / or a propylene copolymer consisting of at least 90 wt% of propylene monomer units and at most 10 wt% of comonomer units selected from ethylene monomer units and a-olefin monomer units having 4 to 10 carbon atoms, for example consisting of at least 95 wt% of propylene monomer units and at most 5 wt% of the comonomer units, based on the total weight of the propylene-based matrix.

[0026] Preferably, the comonomer in the propylene copolymer of the propylene-based matrix is selected from the group of ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1- heptene and 1 -octene, and is preferably ethylene.

[0027] Preferably, the propylene-based matrix consists of a propylene homopolymer. The fact that the propylene-based matrix consists of a propylene homopolymer is advantageous in that a higher stiffness is obtained compared to the case where the propylene-based matrix is a propylene-a- olefin copolymer.

[0028] 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, and / or for example at most 20 dg / min, at most 10 dg / min, at most 5.0 dg / min, at most 3.0 dg / min, at most 1.0 dg / min, measured according to ISO1133-1:2011 (2.16 kg / 230°C).

[0029] Preferably, the propylene-based matrix is present in an amount of 60 to 98 wt%, for example at most 97 wt%, at most 96 wt%, at most 95 wt%, at most 93 wt% or at most 91 wt%, based on the total heterophasic propylene copolymer. Preferably, the propylene-based matrix is present in an amount of at least 70 wt%, more preferably at least 75 wt%, for example at least 80 wt%, at least 85 wt%, at least 87 wt% or at least 90 wt%, based on the total heterophasic propylene copolymer.

[0030] 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.

[0031] 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.

[0032] Preferably, the amount of ethylene monomer units in the ethylene-a-olefin copolymer is 10 to 60 wt%, preferably 20 to 40 wt%, more preferably 25 to 35 wt% or about 30 wt%. The amount of ethylene monomer units in the dispersed ethylene-a-olefin copolymer in the heterophasic propylene copolymer may herein be sometimes referred as RCC2.

[0033] 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.

[0034] The MFI of the dispersed ethylene a-olefin copolymer (before the heterophasic propylene copolymer is mixed into the composition of the invention), MFIrUbber, may be for example at least 0.001 dg / min, at least 0.03 dg / min or at least 0.05 dg / min, and / or for example at most 0.1 dg / min or 0.01 dg / min. MFIrUbber is calculated according to the following formula:

[0035] Log MFIheterophasic — matrix content Log MFlmatrix MF rubber = 10A(— - - . ras - .te;.r content ” - 0 wherein MFI heterophasic is the MFI (dg / min) of the heterophasic propylene copolymer measured according to ISO1133-1 :2011 (2.16kg / 230°C), MFImat™ is the MFI (dg / min) of the propylene- based matrix measured according to ISO1133-1 :2011 (2.16kg / 230°C), matrix content is the fraction of the propylene-based matrix in the heterophasic propylene copolymer, rubber content is the fraction of the dispersed ethylene-a-olefin copolymer in the heterophasic propylene copolymer. The sum of the matrix content and the rubber content is 1. For the avoidance of any doubt, Log in the formula means log .

[0036] Preferably, the dispersed ethylene-a-olefin copolymer is present in an amount of 2.0 to 40 wt%, for example at least 3.0 wt%, at least 4.0 wt%, at least 5.0 wt%, at least 7.0 wt% or at least 9.0 wt%, based on the total heterophasic propylene copolymer. Preferably, the dispersed ethylene- a-olefin copolymer is present in an amount of at most 20 wt%, more preferably at most 15 wt%, for example at most 13 wt%, at most 11 wt%, or at most 10 wt%, based on the total heterophasic propylene copolymer. This leads to good mechanical properties of the composition according to the invention such as impact strength.

[0037] 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 may be at least 95 wt%, at least 97 wt%, at least 99 wt% or 100 wt% of the heterophasic propylene copolymer.

[0038] Preferably, the heterophasic propylene copolymer has a fraction soluble in p-xylene at 25°C (CXS) measured according to ISO 16152:2005 of 2.0 to 40 wt%, for example 9.0 to 25 wt%.

[0039] Preferably, the amount of ethylene monomer units in the heterophasic propylene copolymer (sometimes referred as TC2) is in the range of 1.0 to 20 wt%, for example 5.0 to 15 wt%, based on the heterophasic propylene copolymer.

[0040] Preferably, the MFI of the heterophasic propylene copolymer is 10 to 100 dg / min, for example 15 to 60 dg / min, such as 20 dg / min, 25 dg / min, 30 dg / min, 35 dg / min, 40 dg / min, 45 dg / min, 50 dg / min, 55 dg / min, measured in accordance with ISO 1133 using a 2.16 kg weight and at a temperature of 230 °C.

[0041] Preferably, the amount of (A) the heterophasic propylene copolymer with respect to the composition of the invention is 60 to 90 wt%, preferably 75 to 85 wt%. In the context of the present invention, the polypropylene composition may also comprise two or more heterophasic polypropylenes (A), each of which and / or a combination of which meets the definitions above.

[0042] Optionally, the composition according to the invention may comprise at least one polypropylene(s) other than the heterophasic polypropylene (A), such as a propylene homopolymer or a propylene copolymer with at most 10 wt% of comonomer units, such as 8 wt%, 6 wt%, 5wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, or 0.1 wt%. The comonomer units may be ethylene monomer units and / or an a-olefin monomer units having 4 to 10 carbon atoms.

[0043] However, the amount of such at least one polypropylene(s) other than the heterophasic polypropylene (A) in the polypropylene composition shall be limited to a minor content, for example, at most 5 wt%, preferably at most 2 wt%.

[0044] (B) First Elastomer

[0045] The composition according to the invention may comprise a first elastomer (B) of ethylene and a-olefin comonomer having 4 to 10 carbon atoms.

[0046] The first elastomer has a density deviation Dev of 0-3%, in which Dev is calculated as follows: Dev = [(density of polypropylene)-(density of elastomer)] / (density of polypropylene)*100%. For example, when the polypropylene (A) has a density of 0.905 g / cm3, and the first elastomer (B) has a density of 0.900 g / cm3, the Dev of the first elastomer (B) is (0.905-0.900) / 0.905*100% = 0.55%.

[0047] In one embodiment, Dev of the first elastomer (B) is 0-2%, for example, 0-1%.

[0048] In one embodiment, the (B) first elastomer is a copolymer of ethylene and octene, preferably 1- octene. In one embodiment, the (B) first elastomer is a copolymer of ethylene and butylene, preferably 1 -butylene.

[0049] In one embodiment, the (B) first elastomer has a density of 0.877-0.950 g / cm3, for example, 0.880-0.900 g / cm3, measured in accordance with ASTM D1505. In one embodiment, the (B) first elastomer has a melt flow rate of 0.1 to 10 dg / min, for example 1 to 5 dg / min, measured in accordance with ASTM D1238 using a 2.16 kg weight and at a temperature of 190 °C.

[0050] In one embodiment, the amount of the (B) first elastomer in the composition is 0 to 30 wt%, for example 5 to 25 wt%, 8 to 20 wt%, or 10 to 16 wt%, with respect to the total composition (100 wt%).

[0051] In one embodiment, the total of (A) and (B) is at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% of the total composition. In a particular embodiment, the polypropylene composition does not comprise (C) nor (D).

[0052] In the context of the present invention, the polypropylene composition may also comprise two or more first elastomers (B), each of which and / or a combination of which meets the definitions above.

[0053] (C) Second Elastomer

[0054] The composition according to the invention may comprise a second elastomer (C) of ethylene and a-olefin comonomer having 4 to 10 carbon atoms. The second elastomer (C) and the first elastomer (B) may be the same type or different types.

[0055] The second elastomer has a density deviation Dev of above 3%, in which Dev is calculated as follows:

[0056] Dev = [(density of polypropylene)-(density of elastomer)] / (density of polypropylene)*100%. For example, when the polypropylene (A) has a density of 0.900 g / cm3, and the second elastomer (C) has a density of 0.860 g / cm3, the Dev of the first elastomer (B) is (0.900-0.860) / 0.900*100% = 4.4%.

[0057] In one embodiment, Dev of the second elastomer (C) is 3.01-12%, for example, 4-8%, 4-6%, or 4-5%. In one embodiment, the (C) second elastomer is a copolymer of ethylene and octene, preferably 1-octene. In one embodiment, the (C) second elastomer is a copolymer of ethylene and butylene, preferably 1 -butylene.

[0058] In one embodiment, the (C) second elastomer has a density of 0.850-0.875 g / cm3, for example, 0.860-0.870 g / cm3, measured in accordance with ASTM D1505.

[0059] In one embodiment, the (C) second elastomer has a melt flow rate of 0.1 to 10 dg / min, for example 1 to 5 dg / min, measured in accordance with ASTM D1238 using a 2.16 kg weight and at a temperature of 190 °C.

[0060] In one embodiment, the amount of the (C) second elastomer in the composition is less than 16 wt%, for example 0 to 12 wt%, 1 to 10 wt%, 2 to 8 wt% or 3 to 5 wt%, with respect to the total composition (100 wt%).

[0061] In one embodiment, the total of (A), (B) and (C) is at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% of the total composition.

[0062] In one embodiment, the amount of an elastomer of ethylene and a-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev above 6% is at most 2 wt%, for example at most 1wt%, or at most 0.1wt%.

[0063] In the context of the present invention, the polypropylene composition may also comprise two or more second elastomers (C), each of which and / or a combination of which meet the definitions above.

[0064] (D) Styrene block copolymer

[0065] The composition according to the invention may comprise a styrene block copolymer (D).

[0066] The styrene block copolymer used in the present invention is a block copolymer comprising a terminal block comprising styrene or alpha-methyl styrene. The block copolymer is preferably selected from the group consisting of polystyrene-polybutadiene, polystyrene- poly(ethylene- propylene) (SEP), polystyrene-polyisoprene, poly(alpha-methylstyrene)- polybutadiene, polystyrene-polybutadiene-polystyrene (SBS), polystyrene-poly(ethylene- butylene)-polystyrene (SEBS), polystyrene-poly(ethylene-propylene)-polystyrene, polystyrene-polyisoprene- polystyrene (SIS), poly(alpha-methylstyrene)-polybutadiene- poly(alpha-methylstyrene) and polystyrene- poly(ethylene-propylene-styrene)-polystyrene.

[0067] One preferred example of the block copolymer is polystyrene-polyisoprene-polystyrene (SIS). However, preferably, the block copolymer comprises a non-terminal block comprising ethylene, for example selected from the group consisting of polystyrene-poly(ethylene- propylene) (SEP), polystyrene-poly(ethylene-butylene)-polystyrene (SEBS), polystyrene- poly(ethylene-propylene)- polystyrene and polystyrene-poly(ethylene-propylene-styrene)- polystyrene. Most preferably, the block copolymer is polystyrene-poly(ethylene-butylene)- polystyrene (SEBS).

[0068] Typically, the block copolymer (D) has a melt flow rate of 1 to 10 dg / min, for example 2 to 5 dg / min as measured according to ISO 1133 using a 2.16 kg weight and at a temperature of 230 °C.

[0069] In the context of the present invention, the amount of styrene or alpha-methyl styrene in the block copolymer (D) is at most 25 wt%, preferably at most 21 wt%, more preferably at most 18 wt%, for example 10 to 16 wt% or 12 to 15 wt%, based on the block copolymer.

[0070] The block copolymer (D) may comprise a non-terminal block comprising ethylene. In this case, the amount of ethylene in the block copolymer may typically be 10-60 wt% based on the block copolymer. The amount of components of the block copolymer (C), such as ethylene, butylene and styrene or alpha-methylstyrene, may be determined by13 C NMR measurements, for example according to the following method: The samples are dissolved in C2D2CI4 at 130°C. 2,6-Di-tert-butyl-p-cresol (DBPC) is added as an internal stabilizer. The13 C NMR measurements are performed on a Bruker500 Avance III NMR spectrometer equipped with a 10mm-diameter cryo-cooled probe head operating at 125°C. The weight percentage of ethylene, butylene and styrene are obtained by analyzing the13 C NMR spectra.

[0071] In one embodiment, the amount of the block copolymer (D) in the composition is 0 to 30 wt%, for example 5 to 25 wt%, 8 to 20 wt%, or 10 to 16 wt%, with respect to the total composition (100 wt%). In one embodiment, the total of (B), (C) and (D) is 10-30 wt%, for example 12-25 wt%, such as 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19wt% or 20 wt%.

[0072] In one embodiment, the total of (A), and (D) is at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% of the total composition. In a particular embodiment, the polypropylene composition does not comprise (B) nor (C).

[0073] In one embodiment, the total of (A), (B), and (D) is at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% of the total composition. In a particular embodiment, the polypropylene composition does not comprise (C).

[0074] In one embodiment, the total of (A), (B), (C) and (D) is at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt%, at least 99.5 wt%, at least 99.9 wt% or 100 wt% of the total composition.

[0075] (E) Filler

[0076] The composition according to the invention may comprise a filler, preferably an inorganic filler.

[0077] Suitable inorganic fillers include talc, chalk, clay, mica, glass fibers and carbon fibers. Preferably, the inorganic filler is talc. In one embodiment, the inorganic filler is mica.

[0078] Preferably, the inorganic filler has a d50 of 1 to 50 pm. D50 is the mean (or median) particle size, i.e. the particle diameter where 50% of the particles are larger and 50% are smaller. This value may be determined e.g. by techniques based on the principle of light diffraction. In one embodiment, the inorganic filler has a D50 of 10-30 pm, such as 20 pm.

[0079] In one embodiment, the amount of the filler (E) in the composition is 0-10 wt%, for example 0.1- 10 wt%, 0.1 to about 5 wt%, or from about 0.2 to about 3 wt%, based on the total composition.

[0080] (F) Additives

[0081] The composition may further comprise optional components different from the polypropylene (A), the first elastomer (B), the second elastomer (C), the styrene block copolymer (D) and the filler (E), such as additives (F), wherein the total of (A), (B), (C), (D), (E) and (F) is 100 wt% of the total composition. Accordingly, the invention relates to a composition consisting of (A), (B), (C), (D), (E) and (F).

[0082] The additives may include nucleating agents, stabilizers, e.g. heat stabilizers, antioxidants, UV stabilizers; colorants, like pigments and dyes; clarifiers; surface tension modifiers; lubricants; flame-retardants; mold-release agents; flow improving agents; plasticizers; anti-static agents; blowing agents; and / or components that enhance interfacial bonding between polymer and filler, such as a maleated polypropylene.

[0083] The skilled person can readily select any suitable combination of additives and additive amounts without undue experimentation. The amount of the additives depends on their type and function and typically is of from 0 to about 10 wt%. The amount of the additives may e.g. be from about 0.1 to about 5 wt%, or from about 0.2 to about 3 wt%, based on the total composition.

[0084] Process

[0085] The composition of the invention may be obtained by a process comprising melt-mixing the components of the composition 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 component (A), optional component (B), optional component (C), optional component (D), optional component (E) and optional component (F). For example, when the composition comprises components (A), (B), (D) and (F), the process comprises melt mixing component (A), component (B), component (D) and component (F).

[0086] The melt-mixing step may be preceded by dry-mixing of the components (A), (B) and (C), if applicable. This is especially preferred when the melt-mixing is performed by injection molding.

[0087] 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. With melt-mixing, it is meant that the components are mixed 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 of 200 to 260°C.

[0088] 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.

[0089] In one embodiment, the polypropylene composition of the present invention has a transmittance, measured in accordance with ASTM D1003A at 23°C, of at least 50%, preferably at least 55%, more preferably at least 60%, even more preferably at least 65%, and at most 90%.

[0090] In one embodiment, the polypropylene composition of the present invention has a 100% YD curve type as measured in accordance with ISO 6603-2 at -10°C.

[0091] In one embodiment, the polypropylene composition of the present invention has an at least 80%, preferably 100% YD curve type as measured in accordance with ISO 6603-2 at -20°C.

[0092] In one embodiment, the polypropylene composition of the present invention has an at least 80%, preferably 100% YD curve type as measured in accordance with ISO 6603-2 at -30°C.

[0093] In one embodiment, the polypropylene composition of the present invention has a Charpy impact strength above 20 kJ / m2, as measured in accordance with ISO 179-1eA (II) (2010) at 23°C.

[0094] Further aspects

[0095] The invention further relates to an article, preferably automotive exterior parts like panels and bumpers, and / or automotive interior parts like instrument panels and lighting, prepared from the composition according to the invention.

[0096] The invention further relates to use of the composition according to the invention for automotive exterior parts and / or automotive interior parts. 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.

[0097] 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. 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.

[0098] The invention is now elucidated by way of the following examples, without however being limited thereto.

[0099] Experiments

[0100] Components used in the experiments are summarized in Table 1. In all tables, “%” means “wt%”, unless indicated otherwise.

[0101] Table 1. Components The PP homopolymer, ICP, elastomers, styrene block copolymers and additives were dry blended, and injection molded. The properties of the compositions were measured as summarized in Table 2.

[0102] The measurements of the properties of the components and compositions were performed as follows:

[0103] • Density was measured according to ASTM D 1505.

[0104] • MFR was measured according to ISO 1133 using a 2.16 kg weight and at a temperature of 230 °C.

[0105] • Charpy impact strength was measured according to ISO 179-1eA (II) (2010) at 23°C and -20°C.

[0106] • Haze and Transmittance were measured by ASTM D1003A at 23°C.

[0107] MAI (Multiaxial impact)

[0108] Multiaxial impact is also termed in Dutch as val energie meting (VEM). The MAI / VEM test was conducted respectively on five samples according to ISO 6603-2 at -10°C.

[0109] The ISO 6603-2 curve type evaluation is a common method to characterize the force / deflection data obtained by puncture test experiments. It provides four typical types of curve progression that can usually be observed during data evaluation. In general, these range from ductile to brittle and focus on information like yielding, crack initiation and crack propagation. Obtained data was divided into four break types summarized below:

[0110] YD: Yielding followed by deep drawing (Ductile) - most preferred

[0111] YS: Yielding followed by stable cracking (Semi-ductile) - preferred

[0112] YU: Yielding followed by unstable cracking (Semi-brittle) - least preferred NY: No yielding (Brittle) - not preferred.

[0113] The percentage of YD samples in the five samples tested was reported.

[0114] Table 2. Compositions and properties

[0115] As can be seen from a comparison between comparative example 1 (CE1), CE2, CE3 and CE4, the addition of some polyolefin elastomers, although improves the impact strength, drastically deteriorates the transmittance of the composition.

[0116] From E5 to E7, it can be seen that the use of polyolefin elastomers with a lower density Dev unexpectedly improves the transmittance of the PP composition, contrary to common knowledge in the field. Meanwhile, impact strength of the composition is also improved.

[0117] From E8 to E12, it can be seen that the use of styrene block copolymers in place of or in addition to the low Dev elastomers achieves an even better balance between unexpectedly improved transmittance, improved room temperature Charpy impact strength and low temperature VEM ductility, in which E10 achieves a 100% YD curve type (most preferred ductile curve) at a temperature as low as -30°C.

Claims

Claims:

1. A polypropylene composition comprising:(A) a heterophasic polypropylene consisting of 60-98 wt% of a propylene-based matrix and 2-40 wt% of a dispersed ethylene-a-olefin copolymer, wherein the propylene-based matrix consists of a propylene homopolymer and / or a propylene copolymer consisting of at least 90 wt% of propylene monomer units and at most 10 wt% of comonomer units selected from ethylene monomer units and a-olefin monomer units having 4 to 10 carbon atoms, wherein the amount of ethylene monomer units in the ethylene-a-olefin copolymer is 10 to 60 wt%, and the a-olefin in the ethylene-a-olefin copolymer is chosen from the group of a-olefins having 3 to 8 carbon atoms, and at least one of (B), (C) and (D),(B) a first elastomer of ethylene and a-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev of 0-3%,Dev = [(density of polypropylene)-(density of elastomer) ] / (density of polypropylene)*100%,(C) a second elastomer of ethylene and a-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev of above 3%,(D) a block copolymer comprising a terminal block comprising styrene or alpha-methyl styrene, wherein a sum of (B), (C) and (D) is in the range of 10-30 wt% of the polypropylene composition, and the amount of (C) is less than 60 wt% of the sum of (B), (C) and (D).

2. The polypropylene composition of claim 1 , further comprising:(E) 0-10 wt% of a filler, preferably selected from the group consisting of talc and mica, and(F) 0-10 wt% of additives, and a sum of (A), (B), (C), (D), (E) and (F) is 100%.

3. The polypropylene composition of any of the preceding claims, wherein the amount of (A) is in the range of 60-90 wt% of the polypropylene composition.

4. The polypropylene composition of any of the preceding claims, wherein the polypropylene (A) has a density of 0.890-0.950 g / cm3, and / or a melt flow rate of 10 to 100 dg / min, for example 15 to 60 dg / min, measured in accordance with ISO 1133 using a 2.16 kg weight and at a temperature of 230 °C.

5. The polypropylene composition of any of the preceding claims, wherein an amount of a polypropylene other than heterophasic polypropylene (A) is at most 5 wt%, preferably at most 2 wt%.

6. The polypropylene composition of any of the preceding claims, wherein the first elastomer (B) is a copolymer of ethylene and octene or a copolymer of ethylene and butylene.

7. The polypropylene composition of any of the preceding claims, wherein the first elastomer (B) has a density of 0.877-0.950 g / cm3, and / or a melt flow rate of 0.1 to 10 dg / min, for example 1 to 5 dg / min, measured in accordance with ASTM D1238 using a 2.16 kg weight and at a temperature of 190 °C.

8. The polypropylene composition of any of the preceding claims, wherein the second elastomer (C) is a copolymer of ethylene and octene or a copolymer of ethylene and butylene.

9. The polypropylene composition of any of the preceding claims, wherein the second elastomer (C) has a density of 0.850-0.875 g / cm3, and / or a melt flow rate of 0.1 to 10 dg / min, for example 1 to 5 dg / min, measured in accordance with ASTM D1238 using a 2.16 kg weight and at a temperature of 190 °C.

10. The polypropylene composition of the preceding claims, wherein the block copolymer (D) has a polystyrene content of at most 25 wt%, preferably at most 18 wt%, more preferably at most 15 wt%, and / or the (D) block copolymer is SEBS.

11. The polypropylene composition of any of the preceding claims, wherein a sum of (B), (C) and (D) is in the range of 12-25 wt% of the polypropylene composition.

12. The polypropylene composition of any of the preceding claims, wherein the amount of(C) is less than 50 wt%, preferably less than 30 wt%, more preferably less than 10 wt%, even more preferably being 0%, of the sum of (B), (C) and (D).

13. The polypropylene composition of any of the preceding claims, wherein the amount of(B) is in the range of 3-20 wt%, preferably 5-16 wt% of the polypropylene composition.

14. The polypropylene composition of any of the preceding claims, wherein the amount of(D) is in the range of 3-20 wt%, preferably 5-16 wt% of the polypropylene composition.

15. The polypropylene composition of any of the preceding claims, wherein the amount of(C) is less than 12 wt% of the polypropylene composition, and / or the amount of an elastomer of ethylene and a-olefin comonomer having 4 to 10 carbon atoms with a density deviation Dev above 6% is at most 2 wt%.

16. The polypropylene composition of any of the preceding claims, having a transmittance, measured in accordance with ASTM D1003A at 23°C, of at least 50%, preferably at least 55%, more preferably at least 60%, even more preferably at least 65%, and at most 90%.

17. A process for preparing the polypropylene composition of any of the preceding claims, comprising melt-mixing the components (A)-(F), when applicable.

18. An article comprising the composition according to any one of claims 1-15, which is an automotive exterior or interior part.

Images