Process for producing a polypropylene composition and polypropylene composition produced thereby

Abstract

A process for producing a polypropylene composition using a compounding extruder comprising a) a melting section (100) comprising a first elongated cylindrical tube having an end with a first inlet (101), an end with a first outlet (102) and a first screw; b) a mixing section (200) comprising a second elongated cylindrical tube having an end with a second inlet (201), an end with a second outlet (202), side inlets (204, 205, 206) between the second inlet and the second outlet and a second screw, wherein the process comprises the steps of: A) feeding a propylene-based polymer and optionally additives to the first inlet and discharging a first melt composition from the first outlet, wherein the first screw is operated at a first screw speed, and B) feeding the first melt composition from the first outlet to the second inlet and feeding other components to the side inlets, and discharging a second melt composition from the second outlet, wherein the second screw is operated at a second screw speed which is less than the first screw speed.

Description

[0001] This invention relates to a method for producing polypropylene compositions using a compounding extruder. The invention also relates to such polypropylene compositions and articles comprising such polypropylene compositions.

[0002] Polypropylene compositions are typically prepared by melt-blending polypropylene granules with other components, such as additives and fillers, using a compounding extruder. This is usually done in a compounding extruder that includes a melting section and a mixing section, where the polymer is added and melted in the melting section and the melted polymer is mixed with the other components in the mixing section. The screw extends through the melting and mixing sections, melting and mixing both. After the mixing section, there are usually venting and degassing sections. Finally, a homogeneous polymer composition melt is extruded from the extruder.

[0003] "Influence of the Conditions of Corotating Twin-Screw Extrusion for Talc-Filled Polypropylene on Selected Properties of the Extrudate", Polymers 2019, 11, 1460. This paper uses a conventional compounding extruder and investigates the effects of various parameters on the properties of talc-filled polypropylene obtained through extrusion. In the conclusion (page 16), the paper mentions the negative impact of high screw speeds on polymer properties due to polymer degradation.

[0004] Known methods of producing polypropylene compositions have this problem: increasing output by applying higher screw speeds leads to a deterioration in the properties of the resulting polymer composition. For example, polypropylene compositions produced at high output rates may have lower mechanical properties and / or flame retardancy.

[0005] Furthermore, obtaining polypropylene compositions with reduced odor has been a challenge. Polypropylene compositions tend to have various types of unpleasant odors, which are particularly undesirable in consumer applications such as automotive interior components like dashboards.

[0006] The object of the present invention is to provide a method for producing polypropylene compositions in which the above and / or other problems are solved.

[0007] Therefore, the present invention provides a method for producing polypropylene compositions using a compounding extruder, the extruder comprising:

[0008] a) Melting zone, including

[0009] ai) A first slender cylindrical tube, which has

[0010] - An end having a first inlet configured to receive, during operation, a propylene-based polymer and optional additives, and

[0011] - An end having a first outlet configured to discharge, during operation, a first melt composition comprising a propylene-based polymer and optional additives, and

[0012] aii) A first screw disposed in a first elongated cylindrical tube and having a first length L1, a first screw outer diameter Do1, and a first screw inner diameter Di1, the first screw being configured to deliver a propylene-based polymer and optional additives to a first outlet during operation, and

[0013] b) Mixed sections, including

[0014] bi) a second slender cylindrical tube, which has

[0015] - An end having a second inlet configured to receive a first melt composition from a first outlet during operation.

[0016] - The end with a second outlet, and

[0017] - A side inlet between the second inlet and the second outlet, configured to receive other components during operation.

[0018] The second outlet is configured to discharge, during operation, a second melt composition comprising the first melt composition and other components, and

[0019] A second screw (bii) is arranged in a second elongated cylindrical tube and has a second length L2, a second screw outer diameter Do2, and a second screw inner diameter Di2. The second screw is configured to deliver the first melt composition and other components to a second outlet during operation.

[0020] The first and second screws can operate at different screw speeds.

[0021] The method includes the following steps:

[0022] A) A propylene-based polymer and optional additives are fed into a first inlet and a first melt composition is discharged from a first outlet, wherein a first screw operates at a first screw speed, and

[0023] B) The first melt composition from the first outlet is fed into the second inlet, and other components are fed into the side inlet, and the second melt composition is discharged from the second outlet, wherein the second screw operates at a second screw speed less than that of the first screw, and

[0024] C) Optionally, the second melt composition is formed into granules.

[0025] This invention is based on the understanding that melting polypropylene and mixing polypropylene melts require different conditions than other components to achieve optimal results. Melting polypropylene at high screw speeds is advantageous, resulting in rapid melting and high yield. However, it has been recognized that mixing at high screw speeds can degrade other components to be mixed with polypropylene. This is especially true for large-diameter extruders.

[0026] The inventors have realized that different optimal conditions can be applied for melting and mixing by using different screws that operate at different speeds. Melting can be carried out using a screw running at a higher screw speed, while mixing can be carried out using a screw running at a lower screw speed.

[0027] The low screw speed in the mixing zone produces gentle mixing and a long residence time, both of which allow for better blending of the propylene-based polymer with other components. The low screw speed in the mixing zone further prevents breakage and thermal degradation of components sensitive to mechanical stress or heat. This has been found to improve a variety of properties of the resulting compositions, such as odor, mechanical properties, and / or flame retardancy.

[0028] Furthermore, this invention offers great flexibility in the preparation of various polypropylene compositions. Various polypropylene compositions can be prepared by varying the screw speeds of the first and second screws, rather than designing screws for different polypropylene compositions.

[0029] The mixing section has a side inlet between the second inlet and the second outlet, whereby the side inlet receives the first melt composition downstream of the second inlet. This location of the side inlet results in a particularly favorable composition, especially when glass fibers are fed into the side inlet. Adding glass fibers upstream of the inlet for receiving the melt composition results in a reduction in fiber length, which degrades the properties of the final composition. Furthermore, adding filler (such as talc) upstream of the inlet for receiving the melt composition increases damage to the screw due to friction with the filler.

[0030] It should be understood that US20060245294 describes a method for melting and homogenizing multimodal or bimodal polyolefins in a first extruder and a second extruder, the second extruder being downstream of it in the conveying direction, wherein the shear rate of the first extruder is higher than that of the second extruder. According to US20060245294, homogeneous multimodal or bimodal polyolefins are obtained. US20060245294 does not involve a compounding process in which the polymer is mixed with other components. US20060245294 does not disclose feeding other components from a side feeder of the second extruder.

[0031] It should also be understood that EP2995436 discloses a method for producing a filled polymeric composite material containing a polymeric carrier material and a fibrous material as fillers. The apparatus includes a first extrusion unit having an inlet for the polymeric carrier material and an outlet for the molten polymeric carrier material, a melt processing unit connected to the outlet of the first extrusion unit, and a second extrusion unit. The second extrusion unit has a melt inlet connected to the outlet of the melt processing unit and a fibrous material inlet for the fibrous material. The fibrous material inlet of EP2995436 is arranged upstream of the melt inlet, which is contrary to the present invention requiring a side inlet between the inlet and outlet in the mixing section. EP2995436 does not disclose that the second extrusion unit operates at a screw speed lower than that of the first extrusion unit. EP2995436 also does not address the problem of achieving higher yields and better properties of propylene-based polymer compositions.

[0032] extruder

[0033] The compounding extruder used in the method according to the invention comprises: a) a melting section and b) a mixing section. The mixing section is disposed downstream of the melting section in the conveying direction.

[0034] The melting section includes ai) a first elongated cylindrical tube and aii) a first screw arranged in the first elongated cylindrical tube.

[0035] The first elongated cylindrical tube has an end with a first inlet and an end with a first outlet. The first inlet is configured to receive, in operation, a propylene-based polymer and optionally additives. The first inlet is also configured to optionally receive other polymers in operation.

[0036] The first screw is configured to deliver a propylene-based polymer and optional additives and other optional polymers to a first outlet during operation. During operation, the propylene-based polymer melts as it is delivered to the first outlet. The first outlet is configured to discharge a first melt composition comprising the melt of the polymer and optional additives and other optional polymers during operation.

[0037] The first slender cylindrical tube may have a vacuum degassing section between the first inlet and the first outlet.

[0038] For example, the discharged first melt composition is transferred to the mixing section by heating the transition connector.

[0039] The mixing section includes: bi) a second elongated cylindrical tube and bii) a second screw arranged in the second elongated cylindrical tube.

[0040] The second elongated cylindrical tube has an end with a second inlet and an end with a second outlet. The second inlet is configured to receive a first melt composition from the first outlet during operation. The second elongated cylindrical tube also has a side inlet between the second inlet and the second outlet, which is configured to receive other components during operation.

[0041] The second screw is configured to mix the first melt composition with other components during operation and deliver it to the second outlet. The second outlet is configured to discharge a second melt composition comprising the first melt composition and other components during operation.

[0042] The second slender cylindrical tube may have a vacuum degassing section between the side inlet and the second outlet.

[0043] The first screw has a first length L1, a first screw outer diameter Do1, and a first screw inner diameter Di1. The second screw has a second length L2, a second screw outer diameter Do2, and a second screw inner diameter Di2. The first screw and the second screw can operate at different screw speeds.

[0044] In the method according to the invention, the first screw operates at a screw speed higher than that of the second screw. The screw design of the first and second screws is selected such that the mixing section can handle input from the melting section and any input from the side inlet.

[0045] In some implementations, the first screw has a much smaller free volume than the second screw, allowing the second screw to handle the input. This is advantageous when the first screw operates at a very high screw speed to achieve high throughput. For example, Do1 is 0.30 to 0.80 × Do2 (i.e., Do1 is (0.30 to 0.80) × Do2, or Do1 is 0.30 to 0.80 times Do2).

[0046] In some embodiments, the dimensions of the first and second screws are optimized according to the present invention to achieve high throughput while avoiding the disadvantages associated with excessively high screw speeds.

[0047] The output of an extruder depends in particular on the screw speed and free volume of the extruder.

[0048] Higher screw speeds in the first screw result in higher output. However, if the first screw operates at very high speeds, the propylene-based polymer and other components added to the first extruder can degrade. Furthermore, the temperature of the first melt composition entering the mixing section can become so high that other components added to the second extruder (e.g., flame retardants) may degrade.

[0049] A larger free volume in the first screw results in higher output. A larger free volume in the extruder is achieved through a larger screw outer diameter and a larger ratio between the screw outer diameter and the screw inner diameter.

[0050] To melt polymers, extruders with a smaller diameter ratio are typically used. Due to the smaller diameter ratio, these extruders have higher specific torque levels because more "metal" can be used as structural material in the screw to handle these high torque levels. Greater torque means more energy to melt the polymer, which in turn allows for higher yields during melting. Similarly, a smaller diameter ratio makes melting more efficient because the average overall shear rate is highest when the diameter ratio is at its smallest.

[0051] Therefore, in some embodiments, the first screw has a relatively large outer diameter to increase the available large free volume, enabling high throughput, while the screw speed of the first screw can be set to a medium level. Thus, in some embodiments, the outer diameter Do1 of the first screw is close to the outer diameter Do2 of the second screw, i.e., Do1 is greater than 0.80 × Do2 (i.e., Do1 is (greater than 0.80) × Do2, or Do1 is greater than 0.80 times Do2), preferably Do1 is 0.82 to 1.2 × Do2 (i.e., Do1 is (0.82 to 1.2) × Do2, or Do1 is 0.82 to 1.2 times Do2). Therefore, the first screw has a free volume slightly larger than, equal to, or slightly smaller than the second screw, rather than a free volume much smaller than the second screw. This allows the first screw to operate at an optimal screw speed, higher than the second screw speed, high enough to achieve high throughput without being too high to cause degradation.

[0052] Preferably, Do1 is at least 0.85 × Do2 (i.e., Do1 is (at least 0.85) × Do2, or Do1 is at least 0.85 times Do2). Preferably, Do1 is at most 1.0 × Do2 (i.e., Do1 is (at most 1.0) × Do2, or Do1 is at most 1.0 times Do2).

[0053] Preferably, Do1 is 0.85 to 1.2 × Do2 (i.e., Do1 is (0.85 to 1.2) × Do2, or Do1 is 0.85 to 1.2 times Do2) or Do1 is 0.82 to 1.0 × Do2 (i.e., Do1 is (0.82 to 1.0) × Do2, or Do1 is 0.82 to 1.0 times Do2). More preferably, Do1 is 0.85 to 1.0 × Do2 (i.e., Do1 is (0.85 to 1.0) × Do2, or Do1 is 0.85 to 1.0 times Do2).

[0054] Preferably, Do1 / Di1 = 0.8 to 1.0 × Do2 / Di2 (i.e., Do1 / Di1 = (0.8 to 1.0) × Do2 / Di2, or Do1 / Di1 is 0.8 to 1.0 times Do2 / Di2). This helps the first screw operate at an optimal screw speed while allowing the mixing section to handle inputs from the melting section and any inputs from the side inlet. Very preferably, Do1 is 0.82 to 1.2 × Do2 (i.e., Do1 is (0.82 to 1.2) × Do2, or Do1 is 0.82 to 1.2 times Do2), and Do1 / Di1 = 0.8 to 1.0 × Do2 / Di2 (i.e., Do1 / Di1 = (0.8 to 1.0) × Do2 / Di2, or Do1 / Di1 is 0.8 to 1.0 times Do2 / Di2).

[0055] Preferably, Do1 / Di1 is 1.4 to 2.1. Preferably, Do2 / Di2 is 1.4 to 2.1.

[0056] The length of the first screw is not critical and can be low. For example, L1 / Do1 can be 10 to 100, preferably 14 to 24.

[0057] The length of the second screw is preferably larger to allow for a longer dwell time. Preferably, L2 / Do2 is greater than L1 / Do1. Preferably, L2 / Do2 is between 30 and 100.

[0058] Each of the melting and mixing sections can be configured as a single-screw extruder or a twin-screw extruder. Twin-screw extruders have a higher mixing capacity than single-screw extruders, but also carry a higher risk of causing degradation of the component being processed, especially when the component is glass fiber.

[0059] In some embodiments, at least the mixing section is configured as a twin-screw extruder. According to the invention, a side inlet is located between the second inlet and the second outlet of the mixing section, which reduces the risk of degradation of other components to be mixed compared to adding other components upstream of the second inlet. Therefore, higher mixing capacity is achieved in these embodiments while having a lower risk of degradation of other components added to the side inlet.

[0060] propylene-based polymers

[0061] The terms “polypropylene” and “propylene-based polymer” are used interchangeably herein. Propylene-based polymers may be, for example, propylene homopolymers, random propylene copolymers, or multiphase propylene copolymers.

[0062] Propylene homopolymers can be obtained by polymerizing propylene under suitable polymerization conditions. Propylene copolymers can be obtained by copolymerizing propylene with one or more other α-olefins, preferably ethylene, under suitable polymerization conditions. The preparation of propylene homopolymers and copolymers is described, for example, in Moore, EP (1996) Polypropylene Handbook. Polymerization, Characterization, Properties, Processing, Applications, Hanser Publishers: New York.

[0063] Random propylene copolymers may include ethylene and / or α-olefins selected from α-olefins having 4 to 10 carbon atoms, preferably ethylene, 1-butene, 1-hexene, or any mixture thereof as comonomers. The amount of comonomer is preferably up to 10% by weight based on the random propylene copolymer, for example, 2 to 7% by weight based on the random propylene copolymer.

[0064] Polypropylene can be manufactured using any known polymerization technique and any known polymerization catalyst system. Regarding techniques, slurry, solution, or gas-phase polymerization may be mentioned; regarding catalyst systems, Ziegler-Natta, metallocene, or single-point catalyst systems may be mentioned. All of these are known in the art.

[0065] Multiphase propylene copolymers are generally prepared in one or more reactors by polymerizing propylene in the presence of a catalyst and subsequently polymerizing an ethylene-α-olefin mixture. The resulting polymeric material is multiphase, but its specific morphology usually depends on the preparation method and the monomer ratios used.

[0066] Multiphase propylene copolymers can be produced using any conventional techniques known to those skilled in the art, such as multi-stage process polymerization, including bulk polymerization, gas-phase polymerization, slurry polymerization, solution polymerization, or any combination thereof. Any conventional catalyst system can be used, such as Ziegler-Natta or metallocene. Such techniques and catalysts are described, for example, in WO06 / 010414; Polypropylene and other Polyolefins Ser van der Ven, Studies in Polymer Science, 7, Elsevier, 1990; WO06 / 010414, US4399054 and US4472524.

[0067] Preferably, a Ziegler-Natta catalyst is used to prepare the multiphase propylene copolymer.

[0068] Multiphase propylene copolymers can be prepared by a method including the following steps:

[0069] - Propylene and optionally ethylene and / or α-olefins are polymerized in the presence of a catalyst system to obtain a propylene-based matrix, and

[0070] Subsequently, ethylene and α-olefins are polymerized in a propylene-based matrix in the presence of a catalyst system to obtain dispersed ethylene-α-olefin copolymers. These steps are preferably carried out in separate reactors. The catalyst systems for the first and second steps can be different or the same.

[0071] The multiphase propylene copolymer compositions of the present invention consist of a propylene-based matrix and dispersed ethylene-α-olefin copolymers. The propylene-based matrix typically forms the continuous phase in the multiphase propylene copolymer. The amount of the propylene-based matrix and the dispersed ethylene-α-olefin copolymer can be determined by... 13 The method of determination by C-NMR is also known in this field.

[0072] The propylene-based matrix consists of propylene homopolymers and / or propylene copolymers; the propylene copolymers consist of at least 70% by weight of propylene monomer units and at most 30% by weight of comonomer units selected from ethylene monomer units and α-olefin monomer units having 4 to 10 carbon atoms, based on the total weight of the propylene-based matrix, for example, at least 80% by weight of propylene monomer units and at most 20% by weight of comonomer units, at least 90% by weight of propylene monomer units and at most 10% by weight of comonomer units, or at least 95% by weight of propylene monomer units and at most 5% by weight of comonomer units.

[0073] Preferably, the comonomers in the propylene copolymer based on a propylene matrix are selected from ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene, with ethylene being the most preferred.

[0074] Preferably, the propylene-based matrix is ​​composed of propylene homopolymer.

[0075] Melt flow index (MFI) based on propylene matrix (before incorporating multiphase propylene copolymers into the compositions of this invention) PP The MFI can be measured according to ISO 1133 (2.16 kg / 230°C) at, 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. The MFI can be measured according to ISO 1133 (2.16 kg / 230°C). PPIt can be, for example, 0.1 to 50 dg / min, for example, 0.2 to 40 dg / min, for example, 0.3 to 30 dg / min, for example, 0.5 to 25 dg / min, for example, 1 to 20 dg / min, for example, 1.5 to 10 dg / min.

[0076] The propylene-based matrix may be present, for example, in an amount of 50 to 95% by weight based on the total multiphase propylene copolymer. Preferably, the propylene-based matrix may be present, for example, in an amount of 60 to 85% by weight based on the total multiphase propylene copolymer, for example, at least 65% by weight or at least 70% by weight and / or at most 78% by weight.

[0077] The propylene-based matrix is ​​preferably semi-crystalline, meaning it is neither 100% amorphous nor 100% crystalline. For example, the propylene-based matrix is ​​at least 40% crystalline, such as at least 50%, at least 60%, and / or at most 80% or 70% crystalline. For example, the propylene-based matrix has a crystallinity of 60 to 70%. For the purposes of this invention, the crystallinity of the propylene-based matrix is ​​measured using differential scanning calorimetry (DSC) according to ISO 11357-1 and ISO 11357-3 (1997), using a scan rate of 10 °C / min, a sample size of 5 mg, and a second heating curve using 207.1 J / g as the theoretical standard for 100% crystalline material.

[0078] In addition to the propylene-based matrix, multiphase propylene copolymers also contain dispersed ethylene-α-olefin copolymers. These dispersed ethylene-α-olefin copolymers are also referred to herein as the 'dispersed phase'. The dispersed phase is embedded in the multiphase propylene copolymer in a discontinuous manner. The particle size of the dispersed phase is typically 0.05 to 2.0 micrometers, as can be determined by transmission electron microscopy (TEM). The amount of ethylene-α-olefin copolymer dispersed in the multiphase propylene copolymer is sometimes referred to herein as RC.

[0079] The amount of ethylene monomer units in an ethylene-α-olefin copolymer can be, for example, 20 to 65% by weight. The amount of ethylene monomer units in an ethylene-α-olefin copolymer dispersed in a multiphase propylene copolymer may sometimes be referred to herein as RCC2.

[0080] The α-olefin in the ethylene-α-olefin copolymer is preferably selected from the group consisting of α-olefins having 3 to 8 carbon atoms. Suitable examples of α-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 α-olefin in the ethylene-α-olefin copolymer is selected from the group consisting of α-olefins having 3 to 4 carbon atoms and any mixture thereof; more preferably, the α-olefin is propylene, in which case the ethylene-α-olefin copolymer is an ethylene-propylene copolymer.

[0081] The MFI of the dispersed ethylene α-olefin copolymer (before the multiphase propylene copolymer is incorporated into the composition of the present invention) can 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 MFI of the rubber can be, for example, from 0.001 to 30 dg / min, for example, from 0.01 to 20 dg / min, for example, from 0.1 to 15 dg / min, for example, from 0.3 to 10 dg / min, for example, from 0.7 to 5 dg / min, for example, from 1 to 3 dg / min. The MFI of the rubber is calculated according to the following formula:

[0082]

[0083] in

[0084] MFI (Multiphase Indicator) is the MFI (dg / min) of multiphase propylene copolymers measured according to ISO 1133 (2.16 kg / 230℃).

[0085] MFI matrix is ​​the MFI (dg / min) of a propylene-based matrix measured according to ISO 1133 (2.16 kg / 230℃).

[0086] Matrix content is the fraction of propylene-based matrix in a multiphase propylene copolymer.

[0087] The rubber content is the fraction of ethylene-α-olefin copolymer dispersed in the multiphase propylene copolymer. The sum of the matrix content and the rubber content is 1. To avoid any ambiguity, Log in the formula means log 10 .

[0088] The dispersed ethylene-α-olefin copolymer is present in an amount of 50 to 5% by weight based on the total multiphase propylene copolymer. Preferably, the dispersed ethylene-α-olefin copolymer is present in an amount of 40 to 15% by weight based on the total multiphase propylene copolymer, for example at least 22% by weight and / or for example at most 35% by weight or at most 30% by weight.

[0089] In the multiphase propylene copolymer in the composition of the present invention, the sum of the total weight of the propylene-based matrix and the total weight of the dispersed ethylene-α-olefin copolymer is 100% by weight of the multiphase propylene copolymer.

[0090] Propylene-based polymers may, for example, have a melt flow index of 0.1 to 100 dg / min as determined according to ISO 1133-1:2011.

[0091] In some embodiments, the propylene-based polymer has a melt flow index of 0.1 to 1.0 dg / min as determined according to ISO 1133-1:2011. This invention is particularly advantageous in this case because mixing such a low MFI polymer typically requires high shear, resulting in high heat and thus degradation of the propylene-based polymer.

[0092] In the polypropylene composition produced according to the present invention, the amount of propylene-based polymer relative to the polypropylene composition is preferably at least 30% by weight, more preferably 40 to 95% by weight, for example 50 to 90% by weight or 55 to 85% by weight.

[0093] Other polymers

[0094] According to the present invention, a polypropylene composition is produced by mixing a propylene-based polymer with other components. These other components may include polymers that are not propylene-based.

[0095] Therefore, in some implementations, step A) includes feeding other polymers into the first inlet.

[0096] The amount of other polymers relative to the polypropylene composition is generally less than the amount of propylene-based polymers relative to the polypropylene composition. In the polypropylene composition produced according to the invention, the amount of other polymers relative to the polypropylene composition is preferably 0 to 30% by weight, for example 1 to 20% by weight or 2 to 10% by weight.

[0097] Other polymers can be any type of polymer, but polyolefins are preferred, and polyethylene is particularly preferred. Polyethylene can be selected from high-density polyolefins (HDPE), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and ultra-high molecular weight polyethylene (UHMwPE).

[0098] The production methods of HDPE, LLDPE and LDPE are summarized on pages 43 to 66 of Andrew Peacock’s Polyethylene Handbook (2000; Dekker; ISBN 0824795466).

[0099] HDPE

[0100] HDPE can be a homopolymer of ethylene, or it can contain comonomers such as butene or hexene.

[0101] Preferably, the HDPE has a strength of 940 to 960 kg / m³ as measured according to ISO 1183.3 More preferably 940 to 955 kg / m 3 The density.

[0102] Preferably, the HDPE has a melt flow rate of 0.1 to 4 g / 10 min, more preferably 0.1 to 1 g / 10 min, as measured according to ISO 1133-1:2011 (190°C / 5 kg).

[0103] LLDPE

[0104] Suitable technologies for LLDPE manufacturing include gas-phase fluidized bed polymerization, solution polymerization, polymerization in polymer melts under very high ethylene pressure, and slurry polymerization.

[0105] LLDPE comprises ethylene and C3-C10 α-olefin comonomers (ethylene-α-olefin copolymers). Suitable α-olefin comonomers include 1-butene, 1-hexene, 4-methylpentene, and 1-octene. Preferred comonomer is 1-hexene. Preferably, the α-olefin comonomer is present in an amount of about 5% to about 20% by weight of the ethylene-α-olefin copolymer, more preferably in an amount of about 7% to about 15% by weight of the ethylene-α-olefin copolymer.

[0106] Preferably, LLDPE has a strength of 900 to 948 kg / m³ as determined according to ISO 1872-2. 3 More preferably 915 to 935 kg / m 3 More preferably 920 to 935 kg / m 3 The density.

[0107] Preferably, the LLDPE has a melt flow rate of 0.1 to 3.0 g / 10 min, more preferably 0.3 to 3.0 g / 10 min, as determined according to ISO 1133-1:2011 (190°C / 2.16 kg).

[0108] LDPE

[0109] LDPE can be produced using autoclave high-pressure technology and tubular reactor technology.

[0110] LDPE can be a homopolymer of ethylene or may contain comonomers such as butene or hexene.

[0111] Preferably, LDPE has a strength of 916 to 940 kg / m³ as determined according to ISO 1872-2. 3 More preferably 920 to 935 kg / m 3 The density.

[0112] Preferably, the LDPE has a melt flow rate of 0.1 to 3.0 g / 10 min, more preferably 0.3 to 3.0 g / 10 min, as determined according to ISO 1133-1:2011 (190 °C / 2.16 kg).

[0113] UHMwPE

[0114] UHMwPE is a substantially linear polyethylene with a relative viscosity of 1.44 or higher at a concentration of 0.02% in decahydronaphthalene at 135°C. UHMwPE is further described in ASTM D4020 2011.z.

[0115] additive

[0116] In some implementations, step A) includes feeding the additive into the first inlet.

[0117] In the polypropylene composition produced according to the present invention, the amount of additive relative to the polypropylene composition is preferably 0 to 30% by weight, for example 1 to 20% by weight or 2 to 10% by weight.

[0118] Preferably, the additives include at least one selected from: flame retardants, nucleating agents and clarifying agents, stabilizers, mold release agents, peroxides, plasticizers, antioxidants, lubricants, antistatic agents, crosslinking agents, antiscratch agents, pigments and / or colorants, impact modifiers, foaming agents, deacidifying agents, recycling additives, coupling agents, antimicrobial agents, antifogging additives, slip additives, anti-blocking additives, and polymer processing aids.

[0119] Preferably, the additive includes an impact modifier, which is an elastomer of ethylene and an α-olefin comonomer having 4 to 8 carbon atoms. Advantageously, the method according to the invention produces higher impact strength due to better mixing and less degradation.

[0120] The elastomer may, for example, have a g / cm³ content of 0.850 to 0.915 g / cm³. 3 The density of such elastomers. These types of elastomers are sometimes also called plastic bodies.

[0121] The α-olefin comonomer in the elastomer is preferably a noncyclic monoolefin, such as 1-butene, 1-pentene, 1-hexene, 1-octene or 4-methylpentene.

[0122] Therefore, the elastomer is preferably selected from the group consisting of ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, and mixtures thereof, more preferably wherein the elastomer is selected from ethylene-1-octene copolymers. Most preferably, the elastomer is an ethylene-1-octene copolymer.

[0123] Preferably, the density of the elastomer is at least 0.865 g / cm³. 3 And / or at most 0.910 g / cm³ 3 For example, the density of the elastomer is at least 0.850, for example at least 0.865, for example at least 0.88, for example at least 0.90 and / or for example at most 0.915, for example at most 0.910, for example at most 0.907, for example at most 0.906 g / cm³. 3 More preferably, the density of the elastomer is 0.88 to at most and including 0.907 g / cm³. 3 Most preferably, the density of the elastomer is 0.90 to at most and including 0.906 g / cm³. 3 .

[0124] The elastomer suitable for use in this invention is commercially available, for example, from ExxonChemical, Inc., Houston, Texas, under the trademark EXACT. TM Purchased, or available from Dow Chemical Company, Midland, Michigan, under the trademark ENGAGE. TM The polymer (a series of metallocene-catalyzed plastics) is available, or can be purchased from the MITSUIChemicals Group in Minato, Tokyo, under the trademark TAFMER. TM Purchased, or obtained from SK Chemicals under the trademark Nexlene TM Purchased.

[0125] Elastomers can be prepared using methods known in the art, for example, by using a single-site catalyst, i.e., a catalyst in which the transition metal component is an organometallic compound and at least one ligand has a cyclopentadienyl anionic structure, the ligand being coordinated to the transition metal cation via said anionic structure. This type of catalyst is also known as a "metallocene" catalyst. Metallocene catalysts are described, for example, in U.S. Patent Nos. 5,017,714 and 5,324,820. Elastomers can also be prepared using conventional types of multiphase, multisite Ziegler-Natta catalysts.

[0126] Preferably, the elastomer has a melt flow index of 0.1 to 40 dg / min (ISO 1133, 2.16 kg, 190°C), for example at least 1 dg / min and / or at most 35 dg / min. More preferably, the elastomer has a melt flow index of at least 1.5 dg / min, for example at least 2 dg / min, for example at least 2.5 dg / min, for example at least 3 dg / min, more preferably at least 5 dg / min and / or preferably at most 30 dg / min, more preferably at most 20 dg / min, more preferably at most 10 dg / min, measured according to ISO 1133 using 2.16 kg weight and at 190°C.

[0127] Preferably, the amount of ethylene incorporated into the elastomer is at least 50 mol%. More preferably, the amount of ethylene incorporated into the elastomer is at least 57 mol%, for example at least 60 mol%, at least 65 mol%, or at least 70 mol%. Even more preferably, the amount of ethylene incorporated into the elastomer is at least 75 mol%. The amount of ethylene incorporated into the elastomer can typically be up to 97.5 mol%, for example up to 95 mol% or up to 90 mol.

[0128] In the polypropylene composition produced according to the present invention, the amount of ethylene and the elastomer of the α-olefin comonomer having 4 to 8 carbon atoms relative to the polypropylene composition is preferably 0 to 30% by weight, for example 1 to 20% by weight or 2 to 10% by weight.

[0129] Other components

[0130] One or more other components are fed into the side inlet of the mixing section to mix with the first melt composition. The mixing section may have one, two, three or more side inlets. Different components may be fed into the same or different side inlets.

[0131] In the polypropylene composition produced according to the present invention, the amount of other components fed to the side inlet of the mixing section relative to the polypropylene composition is preferably 1 to 70% by weight, for example 2 to 40% by weight or 3 to 30% by weight.

[0132] Other components can be of various types, such as glass fiber; flame retardants, especially organic flame retardants; and fillers, such as talc, like surface-modified talc.

[0133] The method according to the invention enables the production of compositions with improved properties at high yields because it prevents the breakage or degradation of other components fed to the side inlet during mixing.

[0134] In some embodiments, other components include glass fibers. The low screw speed in the mixing section prevents fiber breakage of the glass fibers, thereby improving the mechanical properties of the resulting composition.

[0135] In some embodiments, other components include flame retardants, particularly organic flame retardants. The low screw speed in the mixing section prevents degradation due to overheating of the flame retardants, especially organic flame retardants, thus improving flame retardancy.

[0136] In some embodiments, other components include surface-modified talc. Surface-modified talc is talc coated with an organic compound (such as silanes, amides, glycols, stearates / esters, sorbates / esters, and titanates / esters). Surface-modified talc is known to those skilled in the art and is commercially available from, for example, Imerys Luzenac. The low screw speed in the mixing section prevents the degradation of the organic compounds, thus avoiding the generation of unpleasant odors.

[0137] In the polypropylene composition produced according to the present invention, when other components include glass fiber, the amount of glass fiber relative to the polypropylene composition is preferably 5 to 50% by weight, for example 10 to 40% by weight or 15 to 35% by weight.

[0138] In the polypropylene composition produced according to the present invention, when other components include an (organic) flame retardant, the amount of the (organic) flame retardant relative to the polypropylene composition is preferably 5 to 50% by weight, for example 10 to 40% by weight or 15 to 35% by weight.

[0139] In the polypropylene composition produced according to the present invention, when other components include fillers, the amount of filler relative to the polypropylene composition is preferably 5 to 50% by weight, for example 10 to 40% by weight or 15 to 35% by weight.

[0140] In some embodiments, the end with the second inlet may also have an inlet prior to the second inlet for receiving additives such as color masterbatch. In this case, these additives are also mixed with the first melt composition in the mixing section of the extruder according to the invention to form part of the second melt composition.

[0141] Other aspects

[0142] The present invention also provides polymer compositions that are obtained or can be obtained by the method according to the invention.

[0143] According to the method of the invention, a polypropylene composition is provided in the form of a second melt composition. In some embodiments, the method according to the invention further includes step C): forming the second melt composition into granules. Therefore, the polypropylene composition according to the invention is provided in granule form.

[0144] Granules can be molded into (semi-)finished products. Suitable examples of molding methods include injection molding, compression molding, extrusion, and extrusion compression molding.

[0145] The present invention also provides articles comprising the polymer composition. For example, articles may be selected from: pipes, automotive exterior parts, automotive interior parts, battery casings in automobiles, household appliances, and building and construction articles.

[0146] Preferably, the polypropylene composition has an odor value of up to 4.0 as determined by VDA270.

[0147] It should be noted that the present invention relates to the subject matter defined by the independent claims alone or in combination with any possible combination of features described herein, preferably, in particular, those combinations of features presented in the claims. Therefore, it is to be understood that all combinations of features relating to compositions according to the invention, all combinations of features relating to methods according to the invention, and all combinations of features relating to compositions according to the invention and features relating to methods according to the invention are described herein.

[0148] It should be further noted that the terms 'comprising' and 'including' do not exclude the presence of other elements. However, it should also be understood that descriptions of products / compositions comprising certain components also disclose products / compositions composed of those components. Products / compositions composed of these components may be advantageous because they provide a simpler and more economical method for preparing the product / composition. Similarly, it should be understood that descriptions of methods including certain steps also disclose methods composed of those steps. Methods composed of these steps may be advantageous because they provide a simpler and more economical method.

[0149] When a value is mentioned for the lower and upper limits of a parameter, it is also understood to mean that the range of combinations of the lower and upper limits is disclosed.

[0150] The invention is now illustrated with the aid of the following figures and embodiments, but the invention is not limited thereto.

[0151] Figure 1 An embodiment of a compounding extruder according to the present invention is shown. The extruder includes a melting section 100 and a mixing section 200.

[0152] The melting section 100 includes a first elongated cylindrical tube and a first screw (not shown) arranged in the first elongated cylindrical tube.

[0153] The first elongated cylindrical tube has an end with a first inlet 101 and an end with a first outlet 102. The first elongated cylindrical tube also has a vacuum degassing section 103 between the first inlet 101 and the first outlet 102.

[0154] The first inlet 101 is configured to receive, in operation, a propylene-based polymer, optional additives, and optional other polymers. The first outlet 102 is configured to discharge, in operation, a first melt composition comprising the components added to the inlet 101.

[0155] The first melt composition discharged from the first outlet 102 is transferred to the mixing section 200 through a heated transition connector.

[0156] The mixing section 200 includes a second elongated cylindrical tube and a second screw (not shown) arranged in the second elongated cylindrical tube.

[0157] The second elongated cylindrical tube has an end with a second inlet 201 and an end with a second outlet 202. The second inlet is configured to receive a first melt composition from the first outlet during operation.

[0158] The second elongated cylindrical tube also has an inlet 203 prior to the second inlet, which is configured to receive additives such as color masterbatch during operation.

[0159] The second elongated cylindrical tube also has three side inlets 204, 205, and 206 between the second inlet 201 and the second outlet 202. For example, side inlets 204 and 205 may be configured to receive fillers such as talc and flame retardants in operation, and side inlet 206 may be configured to receive glass fibers in operation.

[0160] The second slender cylindrical tube also has a vacuum degassing section 207 between the first side inlet 206 and the second outlet 202.

[0161] The second outlet 202 is configured to discharge, during operation, a second melt composition comprising components added from inlets 203, 201, 204, 205 and 206.

[0162] The second melt composition extruded from the second outlet 202 is solidified and cut into granules.

[0163] Referring to the reference numerals mentioned above, the compounding extruder according to the present invention is:

[0164] A method for producing a polypropylene composition using a compounding extruder, the extruder comprising:

[0165] a) Melting section (100), including

[0166] ai) A first slender cylindrical tube, which has

[0167] - An end having a first inlet (101) configured to receive, in operation, a propylene-based polymer and optional additives, and

[0168] - An end having a first outlet (102) configured to discharge, during operation, a first melt composition comprising a propylene-based polymer and optional additives, and

[0169] aii) A first screw arranged in a first elongated cylindrical tube and having a first length L1, a first screw outer diameter Do1, and a first screw inner diameter Di1, the first screw being configured to deliver a propylene-based polymer and optional additives to a first outlet (102) during operation, and

[0170] b) Mixed section (200), including

[0171] bi) a second slender cylindrical tube, which has

[0172] - An end having a second inlet (201) configured to receive a first melt composition from a first outlet (102) during operation.

[0173] - The end with a second outlet (202), and

[0174] - Side inlets (204, 205, 206) between the second inlet (201) and the second outlet (202), the side inlets are configured to receive other components during operation.

[0175] The second outlet (202) is configured to discharge a second melt composition comprising the first melt composition and other components during operation.

[0176] A second screw (bii) is arranged in a second elongated cylindrical tube and has a second length L2, a second screw outer diameter Do2, and a second screw inner diameter Di2. The second screw is configured to deliver the first melt composition and other components to a second outlet (202) during operation.

[0177] The first and second screws can operate at different screw speeds.

[0178] The method includes the following steps:

[0179] A) A propylene-based polymer and optional additives are fed into a first inlet (101) and discharged from a first outlet (102), wherein a first screw operates at a first screw speed, and

[0180] B) The first melt composition from the first outlet (102) is fed into the second inlet (201), and other components are fed into the side inlets (204, 205, 206), and the second melt composition is discharged from the second outlet (202), wherein the second screw operates at a second screw speed less than that of the first screw, and

[0181] C) Optionally, the second melt composition is formed into granules.

[0182] experiment

[0183] A variety of compositions were manufactured using the following two types of compounding extruders.

[0184] Conventional extruder: a compounding extruder with a screw length of 58 L / D, a screw outer diameter of 65 mm and a screw inner diameter of 44.5 mm, two side inlets, atmospheric degassing and vacuum degassing.

[0185] The extruder according to the invention: a compounding extruder having a melting section with a first screw and a mixing section with a second screw, the first screw having a first length of 30L1 / Do1, a first screw outer diameter Do1 of 65 mm and a first screw inner diameter Di1 of 44.5 mm, the second screw having a second length of 58L2 / Do2, a second screw outer diameter Do2 of 65 mm and a second screw inner diameter Di2 of 39.5 mm, two side inlets, atmospheric degassing and vacuum degassing.

[0186] Do1 = 1.0 × Do2

[0187] Do1 / Di1 = 1.46

[0188] Do2 / Di2 = 1.65

[0189] Do1 / Di1 = 0.89 × Do2 / Di2

[0190] Material properties are measured using the following methods:

[0191] According to ISO 180 / 1A (II), Izod impact strength was measured at 23°C and 0°C.

[0192] Charpy impact strength was measured at 23°C, 0°C and -20°C according to ISO 179 / 1eA(II);

[0193] Odor was measured using VDA270.

[0194] Experimental Group A: PP compound with an external elastomer (talc-filled PP)

[0195] The following materials were used:

[0196] PP1: Polypropylene copolymer with an MFI of 33 dg / min (ISO 1133, 230℃ / 2.16 kg);

[0197] HDPE: High-density polyethylene with an MFI of 8 dg / min (ASTM D 1238, 190℃ / 2.16 kg);

[0198] Elastomer: Ethylene-based α-olefin elastomer.

[0199] Comparative Experiment 1 (Conventional Extruder)

[0200] 100 parts by weight of PP1, 13 parts by weight of HDPE, 10 parts by weight of elastomer, 5 parts by weight of color masterbatch and 2 parts by weight of other additives are fed into the inlet of a conventional extruder.

[0201] 32 parts by weight of fine talc were fed into the two side inlets of the extruder, where the mixture was melt-mixed. The screw operated at a screw speed of 600 rpm. A PP composition with a yield of 1000 kg / h was obtained.

[0202] Example 2 (Extruder according to the present invention)

[0203] 100 parts by weight of PP1, 13 parts by weight of HDPE, 10 parts by weight of elastomer, 5 parts by weight of color masterbatch and 2 parts by weight of other additives are fed into the inlet of the melting section of the extruder according to the present invention.

[0204] 32 parts by weight of fine talc were fed into the two side inlets of the mixing section of the extruder according to the invention, and the mixture was melt-mixed. The screw in the melting section ran at a screw speed of 600 rpm. The screw in the mixing section ran at a screw speed of 375 rpm. A PP composition with a yield of 1000 kg / h was obtained.

[0205] The properties of the obtained PP composition were measured and are shown below.

[0206]

[0207] The average value before rounding, determined by a special team based on VDA270.

[0208] It is understood that the composition of Example 2 obtained using the extrusion mechanism according to the present invention has higher impact strength and lower odor compared with the composition of Comparative Experiment 1 obtained using a conventional extrusion mechanism.

[0209] Experimental Group B: Short Glass Fiber (SGF) Reinforced PP Compound

[0210] The following materials were used:

[0211] PP2: Polypropylene homopolymer with an MFI of 47 dg / min (ISO 1133, at 230°C / 2.16 kg);

[0212] SGF: Short-cut glass fiber, 4mm, Ø = 13µm;

[0213] Coupling agent: maleic anhydride-functionalized homopolymer polypropylene.

[0214] Comparative Experiment 3 (Conventional Extruder):

[0215] 100 parts by weight of PP2, 4 parts by weight of coupling agent, 2 parts by weight of color masterbatch and 1.5 parts by weight of other additives are fed into the inlet of a conventional extruder.

[0216] 71 parts by weight of SGF were fed into the second inlet of the extruder, and the mixture was melt-mixed. The screw ran at a screw speed of 400 rpm. A PP composition with a yield of 500 kg / h was obtained.

[0217] Example 4 (Extruder according to the present invention):

[0218] 100 parts by weight of PP2, 4 parts by weight of coupling agent, 2 parts by weight of color masterbatch and 1.5 parts by weight of other additives are fed into the inlet of the melting section of the extruder according to the present invention.

[0219] 71 parts by weight of SGF were fed into the second side inlet of the mixing section of the extruder according to the invention, and the mixture was melt-mixed. The screw in the melting section ran at a screw speed of 400 rpm. The screw in the mixing section ran at a screw speed of 200 rpm. A PP composition with a yield of 600 kg / h was obtained.

[0220] The properties of the obtained PP composition were measured and are shown below.

[0221]

[0222] The average value before rounding, determined by a special team based on VDA270.

[0223] It is understood that the composition of Example 4 obtained using the extrusion mechanism according to the present invention has higher impact strength and lower odor compared with the composition of Comparative Experiment 3 obtained using a conventional extrusion mechanism.

[0224] Experimental Group C: Flame-retardant short glass fiber (SGF) reinforced PP compounds

[0225] The following materials were used:

[0226] PP2: Polypropylene homopolymer with an MFI of 47 dg / min (ISO 1133, at 230°C / 2.16 kg);

[0227] FR: Nitrogen- and phosphorus-based flame retardants;

[0228] SGF: Short-cut glass fiber, 4mm, Ø = 13 µm;

[0229] Coupling agent: maleic anhydride-functionalized homopolymer polypropylene.

[0230] Comparative Experiment 5 (Conventional Extruder):

[0231] 100 parts by weight of PP2, 7 parts by weight of coupling agent, 5 parts by weight of color masterbatch and 2 parts by weight of other additives are fed into the inlet of a conventional extruder.

[0232] 45 parts by weight of FR were fed into the first side inlet of the extruder, and 68 parts by weight of SGF were fed into the second side inlet of the extruder. The mixture was melt-mixed. The screw ran at a screw speed of 400 rpm. A PP composition with a yield of 500 kg / h was obtained.

[0233] Example 6 (Extruder according to the present invention):

[0234] 100 parts by weight of PP2, 7 parts by weight of coupling agent, 5 parts by weight of color masterbatch and 2 parts by weight of other additives are fed into the inlet of the melting section of the extruder according to the present invention.

[0235] 45 parts by weight of FR were fed into the first side inlet of the mixing section of the extruder according to the invention, and 68 parts by weight of SGF were fed into the second side inlet of the mixing section of the extruder according to the invention, and the mixture was melt-mixed. The screw in the melting section ran at a screw speed of 400 rpm. The screw in the mixing section ran at a screw speed of 280 rpm. A PP composition with a yield of 500 kg / h was obtained.

[0236] The properties of the obtained PP composition were measured and are shown below.

[0237]

[0238] It can be understood that the composition of Example 6 obtained using the extrusion mechanism according to the present invention has a higher impact strength compared with the composition of Comparative Experiment 5 obtained using a conventional extrusion mechanism.

[0239] In addition, a glow wire flammability test was conducted according to NEN-EN-IEC 60695-2-12:2014. The results are shown below.

[0240]

[0241] It is understood that the composition of Example 6 obtained using the extrusion mechanism according to the present invention has better flame retardancy than the composition of Comparative Experiment 5 obtained using a conventional extrusion mechanism.

[0242] In the compounding extruder according to the invention, Do1 = 1.0 × Do2, Do1 / Di1 = 0.89 × Do2 / Di2. This means that the first screw has a smaller free volume than the second screw, but the difference is not significant. This allows the first and second screws to operate at optimal speeds: the first screw operates at a higher screw speed than the second screw, but the difference in screw speed is not substantial. Operating the first screw at a high screw speed achieves high output while preventing degradation in the melting and mixing sections. Therefore, by using the compounding extruder according to the invention, a polypropylene composition with good properties is obtained in high output.

Claims

1. A method for producing a polypropylene composition using a compounding extruder, said compounding extruder comprising: a) Melting zone, including ai) A first slender cylindrical tube, the tube having - An end having a first inlet configured to receive, during operation, a propylene-based polymer and optional additives, and - An end having a first outlet configured to discharge, during operation, a first melt composition comprising the propylene-based polymer and the optional additives, and aii) A first screw disposed within the first elongated cylindrical tube and having a first length L1, a first screw outer diameter Do1, and a first screw inner diameter Di1, the first screw being configured to deliver the propylene-based polymer and the optional additives to the first outlet during operation, and b) Mixed sections, including bi) a second elongated cylindrical tube, the second elongated cylindrical tube having - An end having a second inlet configured to receive the first melt composition from the first outlet during operation. - The end with a second outlet, and - A side inlet between the second inlet and the second outlet, the side inlet being configured to receive other components during operation. The second outlet is configured to discharge, during operation, a second melt composition comprising the first melt composition and the other components, and A second screw (bii) is arranged in the second elongated cylindrical tube and has a second length L2, a second screw outer diameter Do2, and a second screw inner diameter Di2. The second screw is configured to deliver the first melt composition and the other components to the second outlet during operation. The first screw and the second screw can operate at different screw speeds. The method includes the following steps: A) The propylene-based polymer and the optional additives are fed into the first inlet and the first melt composition is discharged from the first outlet, wherein the first screw operates at a first screw speed, and B) The first melt composition from the first outlet is fed into the second inlet, and the other components are fed into the side inlet, and the second melt composition is discharged from the second outlet, wherein the second screw operates at a second screw speed less than the speed of the first screw, and C) Optionally, the second melt composition is formed into granules; Where Do1 is greater than 0.80 × Do2 to 1.2 × Do2.

2. The method according to claim 1, wherein Do1 is 0.82 × Do2 to 1.2 × Do2.

3. The method according to any one of claims 1-2, wherein Do1 is at least 0.85 × Do2 and / or Do1 is at most 1.0 × Do2.

4. The method according to any one of claims 1-2, wherein Do1 / Di1 = (0.8~1.0) × Do2 / Di2.

5. The method according to any one of claims 1-2, wherein Do1 / Di1 is 1.4 to 2.1 and / or Do2 / Di2 is 1.4 to 2.

1.

6. The method according to any one of claims 1-2, wherein the other component comprises glass fiber.

7. The method according to any one of claims 1-2, wherein the other components include a flame retardant.

8. The method according to any one of claims 1-2, wherein the other component comprises an organic flame retardant.

9. The method according to any one of claims 1-2, wherein the other component comprises a surface-coated talc.

10. The method according to any one of claims 1-2, wherein the propylene-based polymer is selected from propylene homopolymers, propylene random copolymers, and multiphase propylene copolymers and mixtures thereof.

11. The method according to any one of claims 1-2, wherein the propylene-based polymer has a melt flow index of 0.1 to 100 dg / min as determined according to ISO 1133-1:2011.

12. The method according to any one of claims 1-2, wherein the propylene-based polymer has a melt flow index of 0.1 to 1.0 dg / min as determined according to ISO 1133-1:2011.

13. The method according to any one of claims 1-2, wherein the propylene-based polymer has a single-modal molecular weight distribution.

14. The method according to any one of claims 1-2, wherein the additive comprises at least one selected from: flame retardants, nucleating agents and clarifying agents, stabilizers, release agents, peroxides, plasticizers, antioxidants, lubricants, antistatic agents, crosslinking agents, antiscratch agents, colorants, impact modifiers, foaming agents, deacidifying agents, recycling additives, coupling agents, antimicrobial agents, antifogging additives, slip additives, anti-blocking additives, and polymer processing aids.

15. The method according to any one of claims 1-2, wherein the additive comprises pigment.

16. The method according to any one of claims 1-2, wherein the additive comprises an impact modifier and / or an organic flame retardant, said impact modifier being an elastomer of ethylene and an α-olefin comonomer having 4 to 8 carbon atoms.

17. The method according to any one of claims 1-2, wherein the polypropylene composition has an odor value of up to 4.00 as determined by VDA270.

18. The method according to any one of claims 1-2, wherein the polypropylene composition has an odor value of up to 3.90 as determined by VDA270.

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