REDUCTION OF VOC AND FOG VALUES OF CHARGED HETEROPHASIC POLYPROPYLENE BY SEPARATE AERATION OF INDIVIDUAL POLYOLEFIN COMPONENTS

Abstract

A process for reducing the volatile and semi-volatile organic content (VOC and FOG values) of a heterophasic polypropylene composition, the heterophasic polypropylene composition comprising (i) at least 15 wt% of at least one first heterophasic polypropylene; (ii) less than 15 wt% of at least one elastomeric polyolefin; (iii) at least one filler; (iv) optionally polyethylene;and (v) optionally additional polyolefins below 100 µg / g (VOC, VDA 278 October 2011) and below 390 µg / g (FOG, VDA 278 October 2011), the process involving aerating the first heterophasic polypropylene and each additional polyolefin component that is present in an amount of at least 15% by weight relative to the total weight of the heterophasic polypropylene composition, before extruding these aerated components with the at least one elastomeric polyolefin and the at least one filler and the optional polyethylene and / or optional additional polyolefins.;

Description

REDUCTION OF VOC AND FOG VALUES OF CHARGED HETEROPHASIC POLYPROPYLENE BY SEPARATE AERATION OF INDIVIDUAL POLYOLEFIN COMPONENTS Field of invention The present invention relates to a process for obtaining loaded heterophasic polypropylene compositions with low volatile organic compound content and low semi-volatile condensable substance content, determined as VOC content and FOG content according to VDA 278 of October 2011 (VDA = Association of the Automotive Industry (Verband der Automobilindustrie, in German)). Background Polymers resulting from solution or bulk polymerization often contain traces of the medium in which the polymerization reaction took place, as well as low-molecular-weight byproducts of the polymerization process. Various options are known for removing volatile organic compounds (VOCs, VDA 278 October 2011) and semi-volatile organic compounds (FOGs, VDA 278 October 2011) from polyethylene polymers. These include the use of solvents such as water, the use of steam, and the use of high-temperature gas streams in a process called aeration or purging. Examples of general aeration methods can be found in GB 1272778, WO 02 / 088194, WO2004 / 039848, and US 6,218,504. These documents refer specifically to the aeration or purging of polyethylene compositions. Developing aeration processes is challenging because polyolefin polymers have intrinsic stickiness and a tendency to agglomerate above a relatively low temperature. This results in a limited temperature window in which aeration can be carried out. Polyolefins obtained from solution or bulk polymerization processes often have a high volatile organic compound (VOC) content (VDA 278). In situations where it is also important to remove semi-volatile organic compounds (FOG, VDA 278), longer aeration times are often required, as these molecules are, by definition, less volatile and more difficult to remove. However, in order to ensure that the polyolefin composition nRLznn / zznz / e / YiAi retains its desirable properties, such as, e.g.For mechanical properties and scratch resistance, it is important not to remove or eliminate the additives necessary to produce a material with these properties. Polyolefin compositions, such as, e.g., polypropylene compositions, which exhibit a low level of emissions in conventional tests such as VDA 277 and VDA 278, can be roughly divided into two categories: - polyolefins that obtain their low level of emissions from the polymerization process, mainly due to the nature of the catalyst, but also due to the purity of the monomers applied and possibly the selection of additives. - polyolefins and polyolefin compositions that have undergone a post-purification step during or after combining, possibly involving the use of specific substances as carrier liquids or absorbents. For automotive applications, due to increasingly stringent weight requirements, there is a growing trend toward using thin-walled plastic parts. Manufacturing such thin-walled parts by injection molding requires that the constituent polymer resins have a sufficiently low viscosity so that the molten resins can flow easily and uniformly fill the mold cavities without excessive injection pressures. Decreasing the melt viscosity of a polymer resin requires decreasing the molecular weight of the constituent polymer molecules. However, producing polymer resins containing lower molecular weight molecules increases the content of volatile organic compounds (VOCs, VDA 278 October 2011) and semi-volatile organic compounds (FOGs, VDA 278 October 2011) in the resin. Individualized catalytic systems can be used to synthesize polyolefins that have an intrinsically lower FOG and VOC content, although by limiting the choice of catalyst, the ability to adequately tailor the other properties of the polyolefin is restricted. Another common approach to reducing the occurrence of medium VOC and FOG content is the use of additives that act predominantly to adsorb the compounds, thereby reducing their volatility. nRLznn / zznz / e / YiAi Strategies involving specific catalysts or additives are described in documents EP 2154190, EP 0737712, EP 2262858, EP 1498255, EP 2470600 and EP 3260489. Polyolefin particle degassing is another well-known strategy for reducing their volatile content. EP 3126408 discloses a method for producing rheologically modified polypropylene in which a post-reactor treatment is used to reduce FOG and VOC content. This post-reactor treatment involves, first, a viscous reduction step, followed by holding the viscous-reduced polypropylene at 105 °C for at least 48 hours under a purge gas flow. No information is disclosed on VOC values; only residual FOG and peroxide levels are given. WO 2014 / 090856 describes a method for producing low-VOC particles, in which the polymer particles are degassed using a nitrogen gas flow. This degassing step occurs directly on the particles exiting the reactor, before granulation. Since the polymer particle size distribution in the reactor is very variable, it is easy to foresee that degassing these particles carries a risk of particle carryover, and therefore the degassing conditions used must be carefully selected. Information on VOC and FOG values ​​is not disclosed. EP 1671773 discloses a method for degassing polyethylene granules suitable for pipe fabrication. This method involves the use of specific cooling systems for more effective heat transfer between the different stages of the degassing process, resulting in a faster and more energy-efficient process. Limited information is provided on the shape of the degassing silo, and the effect of the process on FOG and VOC content is not specifically discussed. In each of the preceding examples, simple polymer granules (or particles) are provided, which, after degassing, can then be used directly for the production of articles. The degassing of more complex polymer systems and the potential problems that might arise are not considered. As discussed above and in the cited documents of the above-mentioned technique nRLznn / zznz / e / YiAi, the suitable conditions for aeration of polymer granules are restricted by the tendency of the granules to become sticky and agglomerate. This is particularly the case for polymer compositions containing low-melting-point elastomers, such as heterophasic compositions. On the other hand, more complex compositions, which include multiple polymers produced in separate polymerizations, also invariably contain a number of common additives, such as fillers, pigments, nucleating agents, antioxidants, stabilizers, slip agents, and so on. In some cases, these additives may themselves be volatile, and therefore care must be taken during the blending stage to ensure that sufficient additives are used so that an aeration process does not deplete them too significantly. Finally, it is obvious that not all components of a complex polymer composition will require aeration. The aeration of complex composite compositions, currently the conventional method in the art, could therefore be improved. The present invention is based on the finding that by aerating only certain components of a complex composition, more efficient degassing can be achieved. While it is expected that less degassing will result in a faster process, it is an unexpected effect that the efficiency of VOC and FOG reduction does not decrease significantly in line with the reduced degassing. In particular, notable improvements in efficiency can be achieved when considering loaded heterophase compositions. When maximum reduction of VOC and FOG content is desired, the entire loaded heterophasic polypropylene composition can undergo an aeration process. However, such a process is relatively expensive due to limited space and time efficiency. First, the filler reduces the available space. Second, the added elastomeric components typically require relatively low temperatures, which again limits space and time efficiency. Summary of the invention The present invention is based on the finding that the reduction of volatile and semi-volatile organic content (VOC and FOG values) for complex polymer mixtures can be achieved more efficiently by selectively aerating certain polymer components, while other components do not need to be aerated so that the final blended composition achieves the desired overall VOC and FOG values. The present invention insofar as it provides a process for reducing the volatile and semi-volatile organic content (VOC and FOG values) of a heterophasic polypropylene composition, the heterophasic polypropylene composition comprising (i) at least 15% by weight of at least one first heterophasic polypropylene; (ii) less than 15% by weight of at least one elastomeric polyolefin, (iii) at least one filler; (iv) optionally polyethylene; and (v) optionally additional polyolefins below 100 pg / g (VOC, VDA 278 of October 2011) and below 390 pg / g (FOG, VDA 278 of October 2011), the process comprising the steps of a) aerating the first heterophasic polypropylene through steps a1) to a5) wherein the polyolefin of said steps is the first heterophasic polypropylene: a1) providing an aeration vessel having - at least one inlet for aeration gas, - at least one exhaust outlet, - an inlet for a polyolefin at the top of the aeration vessel, - an outlet for the polyolefin at the bottom of the aeration vessel; where the polyolefin is present as a compact bed; a 2) initiate a countercurrent flow of the polyolefin and the aeration gas a3) by - feeding the raw polyolefin showing a VOC value greater than 100 pg / g and an FOG value greater than 390 pg / g (VOC and FOG values ​​in accordance with VDA 278 of October 2011) into said aeration vessel from the top, - the supply of aeration gas to said aeration vessel through at least one inlet at the bottom; - the extraction of exhaust gas through the exhaust gas outlet of nRLznn / zznz / e / YiAi; 4) maintain said aeration gas flow for an aeration time of less than 24 hours; 5) extract the aerated polyolefin having a VOC value of less than 100 pg / g and a FOG value of less than 390 pg / g (VOC and FOG values ​​in accordance with VDA 278 of October 2011) through the outlet at the bottom of the aeration vessel; b) repeat steps a1) to a5) for the respective aeration of each additional polyolefin component that is present in an amount of at least 15% by weight with respect to the total weight of the heterophasic polypropylene composition, so that all polyolefin components that are individually present in an amount of at least 15% by weight with respect to the total weight of the heterophasic polypropylene composition are aerated; c) extruding the first extracted heterophasic polypropylene and any additional aerated polyolefin component with at least one elastomeric polyolefin and at least one filler and optional polyethylene and / or additional optional polyolefins if present to produce the heterophasic polypropylene composition having a VOC value below 100 pg / g (VDA 278 October 2011) and a FOG value below 390 pg / g (VDA 278 October 2011). The invention is also directed to a product that can be obtained by the process of the invention, preferably an article, more preferably an article from the interior of a car. The term composition can refer to both homopolymers and copolymers, which may optionally contain other components and / or additives. In the present invention, the term polypropylene encompasses propylene homopolymers and / or propylene copolymers. The term volatile organic compound content or VOC content refers to the toluene equivalent content in an emission sample of material determined according to the recommendation of the German Automotive Industry Association (VDA) 278 of October 2011. VOC content is a measure of emissions from plastic materials such as low-density plastomers, caused by low molecular weight components in the polymeric material, typically alkanes with carbon chain lengths up to C20. These low molecular weight components may be residual monomers, oligomers, additives, plasticizers, and / or degradation products. The expression semi-volatile organic condensable content (FOG content) refers to the equivalent content of n-hexadecane in a material emission sample determined according to the recommendation of the Association of the Automotive Industry, VDA 278 of October 2011. The content of semi-volatile organic compounds is a measure of the emissions of plastic materials, which are caused by medium molecular weight components, such as oligomers, which have a boiling point in the boiling range of alkanes C16 - C32. The term "raw" refers to polyolefins or polyolefin compositions that have not been or have not yet been subjected to an aeration process, as distinct from the aerated polyolefin components of the invention. The term aeration or aeration process, as used herein, denotes a process or process step in which a compound is subjected to a gas flow. This process is carried out in an aeration vessel. The term "aeration gas" as used herein denotes any gas suitable for heating to at least 50°C and suitable for removing volatile organic compounds (VOCs) and condensable semi-volatile organic compounds (FOGs) from polyolefin compositions. Suitable gases include, for example, nitrogen, air, or mixtures thereof. However, in principle, any inert gas may be used. For economic reasons, air is the preferred gas for the process of the present invention. The gas that comes out of the aeration vessel, i.e., the gas that has absorbed the volatile organic compounds (VOCs) and semi-volatile organic condensables (FOGs), is referred to herein as exhaust gas. The percentage reduction in VOC values ​​(i.e., VOC content) according to the present invention is calculated as: Percentage reduction in VOC values ​​(VOC value before aeration — VOC value after aeration — I____________________________________________________________________________________________________) X VOC value before aeration / nRLznn / zznz / e / YiAi The percentage reduction in FOG values ​​(i.e., FOG content) according to the present invention is calculated as: Percentage reduction in FOG values ​​ / FOG value before aeration — FOG value after aeration \ — I--------------------------------------------------------------------------------------------------------------------------I \ FOG value before aeration / In the process according to the present invention, it is preferred that the at least one elastomeric polyolefin and the at least one filler are not aerated. Furthermore, the present invention preferably provides an aeration process, wherein the combined heterophasic polypropylene and any additional aerated polyolefin component constitute 50 to 90% by weight of the heterophasic polypropylene composition. In the process according to the present invention, the first raw heterophasic polypropylene and any other polyolefin components to be aerated, flowing into the aeration vessel, are preferably provided in granule form. The preferred granule diameters, more precisely, the mean particle size, d50, measured according to ISO 3310 and determined by ISO 9276-2, are from 2.5 to 5.0 mm, preferably from 2.5 to 4.5 mm, and most preferably from 2.8 to 4.0 mm. Granules (or granules) often exhibit a considerable gradient in volatile content. As expected, in conventionally produced polyolefin granules, the amount of volatile organic compounds (VOCs) and semi-volatile organic compounds (FOGs) is essentially zero near the surface, while it is considerably higher further from the granule surface. In the process according to the present invention, the granules are optionally pre-heated before being added to the aeration container, such as pre-heated to 40 °C before being added to the aeration container. The present invention provides an aeration process that operates for less than 24 hours, less than 12 hours, or less than 10 hours, such as 3 to 9 hours. The present invention preferably provides a process wherein the temperature of the aeration gas is at least 100°C, or at least 110°C, or at least 115°C. The temperature may be from 100°C to 140°C, or from 110°C to 135°C, or from 115°C to 130°C. The aeration temperature is most preferably 120°C. It is believed that the process according to this invention nRLznn / zznz / e / YiAi, when carried out at 120°C, results in a heterophasic polypropylene composition that maintains the scratch resistance previously exhibited by a heterophasic polypropylene composition that has not undergone the process of the invention.Furthermore, it is believed that at these high temperatures most polymers would melt or, alternatively, be too sticky to be easily handled; consequently, the present process in combination with specific polymers provides process efficiency advantages, while ensuring that the heterophasic polypropylene composition can be easily handled. The present invention optionally provides a process in which the exhaust gas is subjected to a purification stage and recycled back to the inlet for the aeration gas. The present invention optionally provides a process in which the exhaust gas passes through a heat exchanger before being discharged into the atmosphere. The present invention preferably provides a process in which the aeration vessel is a silo, preferably an insulated silo. It should be understood that the use of an insulated silo is preferred for all embodiments described herein. The present invention preferably provides a process in which the aeration vessel is cylindrical or a cylinder with a conical base. Brief description of the figures Figure 1 shows the VOC content of the inventive and comparative examples Figure 2 shows the FOG content of the inventive and comparative examples Detailed description of the invention The process The invention relates primarily to a process for reducing the volatile and semi-volatile organic content (VOC and FOG values) of a heterophasic polypropylene composition, the heterophasic polypropylene composition comprising (i) at least 15% by weight of at least one first heterophasic polypropylene; (i) less than 15% by weight of at least one elastomeric polyolefin, nRLznn / zznz / e / viAi (iii) at least one filler; (iv) optionally polyethylene; and (v) optionally additional polyolefins below 100 pg / g (VOC, VDA 278 of October 2011) and below 390 pg / g (FOG, VDA 278 of October 2011), the process comprising the steps of a) aerating the first heterophasic polypropylene through steps a1) to a5) wherein the polyolefin of said steps is the first heterophasic polypropylene: a1) provide an aeration vessel having at least one inlet for the aeration gas, at least one outlet for the exhaust gas, an inlet for a polyolefin at the top of the aeration vessel, an outlet for the polyolefin at the bottom of the aeration vessel; wherein the polyolefin is present as a compact bed; a2) initiating a countercurrent flow of the polyolefin and the aeration gas a3) by feeding the raw polyolefin showing a VOC value greater than 100 pg / g and a FOG value greater than 390 pg / g (VOC and FOG values ​​in accordance with VDA 278 of October 2011) into said aeration vessel from the top, feeding the aeration gas into said aeration vessel through at least one inlet at the bottom; the extraction of exhaust gas through the exhaust gas outlet; a4) maintain said aeration gas flow for an aeration time of less than 24 hours; a5) extract the aerated polyolefin having a VOC value of less than 100 pg / g and a FOG value of less than 390 pg / g (VOC and FOG values ​​in accordance with VDA 278 of October 2011) through the outlet at the bottom of the aeration vessel; b) repeat steps a1) to a5) for the respective aeration of each additional polyolefin component that is present in an amount of nRLznn / zznz / e / YiAi at least 15% by weight with respect to the total weight of the heterophasic polypropylene composition, so that all polyolefin components that are individually present in an amount of at least 15% by weight with respect to the total weight of the heterophasic polypropylene composition are aerated; c) extruding the first extracted heterophasic polypropylene and any additional aerated polyolefin component with at least one elastomeric polyolefin and at least one filler and optional polyethylene and / or additional optional polyolefins if present to produce the heterophasic polypropylene composition having a VOC value below 100 pg / g (VDA 278 October 2011) and a FOG value below 390 pg / g (VDA 278 October 2011). The effect of the invention is a more effective reduction of VOC and FOG values ​​than that which would be achieved by aerating the granules of the final mixed heterophasic polypropylene composition. While it is obvious that reducing the mass being treated will accelerate the process, i.e., increase the spatiotemporal yield, other factors combine to enhance this increase. By selecting only the components that are the main contributors to the overall FOG and VOC content of the composition, these overall values ​​can be reduced to a satisfactory level without aerating other components. Although the resulting FOG and VOC values ​​of the composition will be higher than if all components were aerated, the values ​​are still more than satisfactory for a composition that will be used in the manufacture of, among other things, automotive parts. The improvement in spatiotemporal yield resulting from the process outweighs the reduced effect of degassing. The improved space-time efficiency offers clear economic advantages, as aeration over relatively short periods requires less energy to supply heated gas. Additionally, less silo space is needed to store the polymer composition compared to longer aeration processes, where larger quantities of the polymer composition must be stored for extended periods. The process of the invention, as indicated above, defines nRLznn / zznz / e / Yi / u that each polyolefin fraction constituting at least 15% by weight of the heterophasic polypropylene composition is aerated by steps a1) to a5). Since the at least one elastomeric polyolefin is present in less than 15% by weight, this means that both it and the filler (which may be present in at least 15% by weight but is not a polyolefin) are not aerated. It is preferred that the total mass of polyolefins to be aerated not be so high as to minimize the efficiency gains of the process of the invention, but equally not so low as to mean that the reduction in VOC and FOG values ​​is insufficient for use, for example, in automotive interiors. Suitablely, the total mass of the compounds to be aerated constitutes 50 to 90% by weight of the heterophasic polypropylene composition. If necessary, it is also theoretically possible to further improve efficiency by tailoring the degassing properties to each individual component, rather than to the stickiest component, as must be done when the composition is aerated as a whole. Furthermore, the aeration process of the present invention also offers advantages in terms of maintaining the structural properties of the heterophasic polypropylene composition and preserving the scratch resistance of the polypropylene material, while also resulting in low levels of VOCs and FOG. It is believed that aeration for extremely long periods with a low-temperature gas or using a gas with a temperature exceeding 140°C would lead to the deterioration of the polypropylene material's properties, such as its scratch resistance. Furthermore, the process according to the present invention does not lead to a significant loss of slip agent, which means that if the heterophasic polypropylene composition is used for injection molding to produce polypropylene articles, it easily detaches from the mold and no polypropylene remains adhered to the surface of the mold. Heterophasic polypropylene composition The heterophasic polypropylene composition of the invention comprises (i) at least 15% by weight of at least one first heterophasic polypropylene; (ii) less than 15% by weight of at least one elastomeric polyolefin; (iii) at least one filler; nRLznn / zznz / e / YiAi (iv) optionally polyethylene; and (v) optionally additional polyolefins The properties of the first heterophasic polypropylene are not particularly limited. The MFR2 can be, for example, from 0.1 to 200 g / 10 min, more preferably from 1.0 to 150 g / 10 min. The density can be from 850 to 930 g / cm3, more preferably from 860 to 910 g / cm3. Examples of suitable heterophasic polypropylenes include, but are not limited to, BG055AI, BF970MO, BJ400HP, ED007HP, EF015AE, and EG050AE, available from Borealis AG, Austria. Heterophasic polypropylene can also be virgin heterophasic polypropylene manufactured in a reactor. Similarly, the at least one elastomeric polyolefin is not particularly limited. Suitable elastomeric polyolefins are often copolymers of ethylene with α-olefin comonomers, for example octene. Some examples of suitable elastomeric polyolefins include Engage 7220, Engage 8100, Engage 8200, and Engage 8401 from Dow Chemical, USA, as well as Queo 8201, Queo 8203, and Queo 8210 from Borealis AG, Austria. The at least one elastomeric polyolefin may also be a virgin elastomeric polyolefin manufactured in a reactor. At least one filler is selected from the group of natural or synthetic non-thermoplastic fillers or reinforcements. Preferably, at least one filler is a mineral filler. It is noted that at least one filler is a phyllosilicate, mica, or wollastonite. Even more preferably, at least one filler is selected from the group consisting of mica, wollastonite, kaolinite, smectite, montmorillonite, and talc. The most preferred at least one filler is talc. Optional polyethylene is typically (when present) in the form of a stock blend formulation for the addition of various additives and stabilizers. Optional additives in heterophasic polypropylene compositions are well-known in the art and may include (but are not limited to) antioxidants, pigments, nucleating agents, and specific additives to improve UV stability and / or scratch resistance. Additives known to improve the scratch resistance of polypropylene compounds include erucamide, glyceryl stearate, and glyceryl monostearate, among others. nRLznn / zznz / e / YiAi Additional polyolefins are not limited and may be, for example, additional heterophasic polypropylenes as described above. The melting point (Tf) of the first unwrought heterophasic polypropylene and all the additional polyolefin components to be aerated is preferably above 150°C, more preferably above 160°C. After aeration, there may be a negligible change in the melting point (Tf) of the polypropylene composition, such as, for example, a reduction of less than 10% in the melting point (Tf), or a reduction of less than 5% in the melting point value, or a reduction of less than 2.5% in the melting point value. The melting point (Tf) of the individual components after aeration is therefore each above 150°C, preferably above 160°C. Without wishing to be bound by any theory, it is believed that the aeration process according to the present invention does not lead to a substantial change in the properties of the individual components, such as, for example,, Tf and, therefore, there would be no substantial change in the properties of the final heterophasic polypropylene composition of the invention with respect to an identical heterophasic polypropylene composition in which no individual component has undergone aeration. The individual aerated components of the heterophasic polypropylene composition of the invention can exhibit FOG values ​​of less than 500 pg / g, preferably less than 450 pg / g, more preferably less than 400 pg / g, and most preferably less than 380 pg / g. Furthermore, the individual aerated components resulting from the inventive process according to steps a1) to a5) can exhibit VOC values ​​of less than 150 pg / g, preferably less than 100 pg / g, more preferably less than 80 pg / g, and most preferably less than 60 pg / g. (Both VOC and FOG values ​​in accordance with VDA 278 of October 2011) In certain embodiments, the inventive process leads to a reduction of the VOC values ​​(VDA 278 of October 2011) of the aerated components of the heterophasic polypropylene composition, in relation to said aerated components before aeration, greater than 50%, preferably greater than 60%, more preferably greater than 70%. In certain embodiments, the inventive process leads to a reduction of the FOG values ​​(VDA 289 of October 2011) of the aerated components nRLznn / zznz / e / YiAi of the heterophasic polypropylene composition, in relation to said aerated components before aeration, greater than 10%, preferably greater than 20%, more preferably greater than 30%. In certain similar embodiments, the inventive process leads to a reduction, in relation to said aerated components before aeration, in the VOC values ​​(VDA 278 of October 2011) of the aerated components of the polypropylene composition of more than 50%, and a reduction in the FOG values ​​(VDA 278 of October 2011) of more than 10%, more preferably a reduction of more than 60% and 20%, respectively, most preferably a reduction in the VOC values ​​(VDA 278 of October 2011) of the aerated components of the polypropylene composition of more than 70%, and a reduction in the FOG values ​​(VDA 278 of October 2011) of more than 30%. The heterophasic polypropylene composition of the invention can exhibit FOG values ​​of less than 390 pg / g, preferably less than 380 pg / g, and most preferably less than 370 pg / g. Furthermore, the heterophasic polypropylene compositions resulting from the inventive process can exhibit VOC values ​​of less than 100 pg / g, preferably less than 90 pg / g. (VOC and FOG values ​​in accordance with VDA 278 of October 2011). In certain embodiments, the inventive process leads to a reduction of the VOC values ​​(VDA 278 of October 2011) of the heterophasic polypropylene composition, in relation to a comparative heterophasic polypropylene composition in which none of the components has undergone aeration, greater than 30%, preferably greater than 40%, more preferably greater than 50%. In certain embodiments, the inventive process leads to a reduction of the FOG values ​​(VDA 289 of October 2011) of the heterophasic polypropylene composition, in relation to a comparative heterophasic polypropylene composition in which none of the components has undergone aeration, greater than 10%, preferably greater than 30%, more preferably greater than 20%, most preferably greater than 30%. In certain similar embodiments, the inventive process leads to a reduction, in relation to a comparative heterophasic polypropylene composition as described above, in the VOC values ​​(VDA 278 October 2011) of the polypropylene composition of more than 30%, and a reduction in the FOG values ​​(VDA 278 October 2011) of more than 10%, more preferably a reduction of more than 40% and 20%, respectively, most preferably a reduction in the VOC values ​​(VDA 278 October 2011) of the polypropylene composition of more than 50%, and a reduction in the FOG values ​​(VDA 278 October 2011) of more than 30%. The process according to the present invention, moreover, does not lead to the depletion of slip agents such as, e.g., erucamide. During the production of polypropylene, slip agents are often added to the polypropylene blend to reduce the coefficient of friction of these polypropylene materials. The most popular slip agents used by the industry are from the chemical group of fatty acid amides, such as, e.g., erucamide. When a slip agent is mixed with a molten polypropylene polymer, it is absorbed into the amorphous regions of the polypropylene polymer. Upon cooling, the slip agent becomes incompatible with the polypropylene material due to the different surface energies of the two materials and migrates to the material's surface. The migration rate depends on the difference between the surface energies of the polypropylene and the slip agent (the greater the difference, the faster the migration). This initially leads to the formation of a monolayer on the polymer surface, followed by the deposition of subsequent layers as new slip agent molecules reach the surface, resulting in the formation of a double layer. Due to the weak bonding between fatty acid amide layers, polypropylene-based materials containing fatty acid amides will slide over one another easily. The presence of a slip agent layer also reduces friction on the surface of the polypropylene composition.This property is also important, for example, when producing injection-molded articles, since slip agents can be used to help release the injection-molded articles from a mold. Fatty acid amides reach the surface of the polypropylene articles as the polypropylene cools, thus reducing the coefficient of friction between the polypropylene article and the mold. This means that with relatively little force, the polypropylene article can be removed from the mold and no polypropylene adheres to the mold when releasing the molded article. nRLznn / zznz / e / Yi / u Many slip agents, particularly fatty acid amides such as, for example, erucamide, are relatively volatile, and therefore care must be taken to prevent these materials from escaping during the processing steps in polymer production. The process according to the present invention does not lead to the depletion of slip agents, particularly fatty acid amides such as, for example, erucamide. Therefore, the process according to the present invention allows for the advantageous removal of volatile and semi-volatile substances without removing slip agents from the polypropylene composition. Accordingly, in the process according to the present invention, the polypropylene composition preferably contains at least one slip agent, more preferably at least one slip agent selected from the group of fatty acid amides, most preferably erucamide. Aeration gas flow In the process according to the present invention, the polyolefin, preferably in granule form, is preferably subjected to a hot gas stream. The present invention preferably provides a process in which the total standardized volumetric air flow used is from 1 to 5 Nm3 / kg, such as at least approximately 1.5 Nm3 / kg, preferably at least approximately 2 Nm3 / kg, such as approximately 2.6 Nm3 / kg. According to the present invention, the gas inlet is located at the bottom of the aeration vessel, resulting in a bottom-to-upward gas flow through the polyolefin composition bed. In the present invention, the gas inlet may preferably be selected from the group of: a nozzle, a series of nozzles, a gas distribution ring, and a gas distribution plate. The process according to the present invention comprises a step of optionally subjecting the gas downstream of the aeration vessel to a means of removing hydrocarbons. Preferably, these means are selected from one or more catalytic oxidation units, one or more carbon absorption columns (drums), and / or any conventional exhaust treatment known in the art. Even more preferably, these means are carbon absorption columns (drums). Preferably, when the aeration gas is air and / or nitrogen, it can be released into the atmosphere after hydrocarbon removal. Additionally, the aeration gas can be treated and recirculated back to the aeration vessel. Furthermore, the heat still contained in the discharged gas can be transferred to the gas used for aeration through heat exchangers known in the art, if the gas extracted from the environment has a temperature lower than the temperature required for the process. In the process according to the present invention, the exhaust gas is preferably discharged into the atmosphere. Alternatively, but less preferably, the exhaust gas is reused after the separation of volatile and semi-volatile substances. Aeration process The present invention preferably provides an aeration process that operates for less than 24 hours, preferably less than 12 hours, more preferably less than 10 hours, and most preferably from 3 to 9 hours. In general, the aeration time is inversely proportional to the gas temperature, meaning a compromise must be reached to prevent the granules from melting and sticking together. Typical values ​​for temperature and residence time for polypropylene, according to EP 1 671 773 A1, are 80 to 110 °C for a period of 10 to 50 hours. It is believed that the reduction of VOC values ​​reaches a plateau after prolonged aeration times of more than five hours under the conditions described herein; conversely, for FOG values, there is a weaker dependence on aeration time in the period of 0 to 5 hours.This is thought to be due to the slow diffusion of higher molecular weight alkanes (C1e - C32), which contribute greatly to FOG values, unlike the rapid diffusion of <25 that are considered for VOC values. In the process according to the present invention, the polyolefin is preferably not mixed or moved throughout the treatment by mechanical means. Consequently, during the aeration process, the polyolefin composition is effectively stationary (apart from its vertical transit through the aeration vessel). Therefore, the present invention preferably excludes processes in which the polymer composition is agitated during aeration; such processes, such as fluidized bed processes, are not within the scope of this invention. The absence of mechanical mixing and similar measures, such as filling, is particularly advantageous as it prevents the formation of fines. Furthermore, the degree of filling is higher without the need for mechanical agitation or the need to transfer the polyolefin composition to another treatment vessel / silo. The present invention optionally provides a process in which the granules are preheated before being added to the aeration vessel, such as by preheating them to at least 40 °C, more preferably by preheating them to temperatures of 80 °C to 100 °C before being added to the aeration vessel. Since the specific heat capacity of the polyolefin composition, along with its mass, is significantly higher than the specific heat capacity of the gas, care must be taken to ensure that the gas stream temperatures at the aeration inlet and outlet are met. Therefore, if the polyolefin composition is supplied to a silo at relatively low temperatures, a preheating stage will be necessary. Preheating can also occur naturally through the gas stream and the temperatures specified above. However, during such preheating, the outlet temperature will be lower as heat is transferred to the polyolefin composition. The polyolefin composition is optionally preheated before the start of the aeration period to accelerate the process. In general, any heating method known in the prior art may be used for preheating. The polyolefin composition may be preheated to temperatures of 40 °C or higher, preferably 50 °C or higher. Preheating could also be considered as preventing the granules, which are produced, extruded, and granulated shortly beforehand, from cooling down. These granules typically have a temperature of approximately 40°C or higher, preferably 50°C or higher. Consequently, the production process of the polyolefin composition and the process of the present invention can be carried out as an integrated process. In contrast, the present invention provides a process in which the polyolefin composition is not preheated before being added to the aeration vessel and in which the polyolefin is heated simply by the flow of heated aeration gas in the silo. Without intending to be bound by any theory, it is believed that with a fairly small granule size (diameter of approximately 3.5 mm), the composition quickly reaches the desired aeration temperature after being added to the aeration vessel. The aeration vessel used in the process of the present invention is not particularly limited and, in principle, any aeration vessel or aeration silo available on the market can be used; in addition, custom-made aeration vessels, which have been built specifically for the purpose of performing aeration, can be used. To shorten the preheating phase, avoid energy loss during aeration, and / or achieve greater homogeneity in the cross-section, the use of an insulated treatment vessel, preferably an insulated silo, is preferred. The silo can be, for example, a steel silo. Furthermore, the silo can be cylindrical or conical in shape. Products and articles One aspect of the present invention also relates to products obtainable by the processes described above and to articles produced using them. Polypropylene is a versatile material that is easily processed and has a number of applications in the automotive industry, e.g., for injection-molded components such as dashboards or interior door trim. Polypropylene compositions are also used as a coating for blister packaging. All preferred intervals and realizations described above also apply to these products and items and are incorporated herein by reference. Experimental section The following examples are included to demonstrate certain aspects and embodiments of the invention as described in the claims. Those skilled in the art will appreciate, however, that the following description is illustrative only and should not be taken in any way as a restriction on the invention. Test methods Sample preparation The VOC values, FOG values ​​and TVOC values ​​were measured nRLznn / zznz / e / YiAi as described below, after the preparation of a sample consisting of injection-molded plates according to EN ISO 19069-2:2016. These plates were packaged in aluminum and composite sheets immediately after production and the sheets were sealed. For thermodesorption analysis according to VDA 278 (October 2011), samples were stored uncovered at room temperature (23 °C max.) for 7 days immediately before the start of the analysis. Regarding the measurements for VDA 277 (January 1995), no additional uncovered storage or other conditioning was carried out. Instead, the injection-molded plates were cut and ground in a Retsch SM-2000 mill. In both cases (VDA 277 and VDA 278), the production date of the injection-molded plates, the time the sample arrived at the laboratory, and the date of analysis were recorded. VOC and FOC according to VDA278 VOC value: It is determined in accordance with VDA 278 of October 2011 from injection-molded plates. VDA 278 of October 2011, Thermal Desorption Analysis of Organic Emissions for the Characterization of Non-Metallic Materials for Automobiles, Automotive Industry Association, VDA. According to VDA 278 of October 2011, the VOC value is defined as the total of easily volatile to moderately volatile substances. It is calculated as toluene equivalents. The method described in this Recommendation allows for the determination and analysis of substances in the boiling / elution range up to n-pentacosane (C25). FOG value: The FOG value is determined according to VDA 278 of October 2011 from injection-molded plates. According to VDA 278 of October 2011, the FOG value is defined as the total of low-volatility substances that elute within the retention time of n-tetradecane (inclusive). It is calculated as hexadecane equivalents. Substances with a boiling point in the C16 to C32 n-alkane boiling range are determined and analyzed. flow index (MFR2): The flow indices were measured with a load of 2.16 kg (MFR2) at 230 °C. nRLznn / zznz / e / viAi The melt flow index is the amount of polymer in grams that the test apparatus standardized according to ISO 1133 extrudes in a period of 10 minutes at a temperature of 230 °C with a load of 2.16 kg. Cold xylene soluble fraction (XCS, % by weight): The cold xylene soluble fraction (XCS) is determined at 23 °C according to ISO 6427. Polymer - puncture plate - instrumented: The puncture energy was determined by an instrumented drop weight test according to ISO 6603-2 using 60x60x1 mm injection-molded plates at a test speed of 2.2 m / s, with a 20 mm diameter lubricated, clamp-mounted striker. The indicated puncture energy is the result of an integral of the failure energy curve measured at (60x60x1 mm). Diameter D A sieve analysis was performed according to ISO 3310. The sieve analysis involved a nested column of wire mesh sieves with the following sizes: >20 µm, >32 µm, >63 µm, >100 µm, >125 µm, >160 µm, >200 µm, >250 µm, >315 µm, >400 µm, >500 µm, >710 µm, >1 mm, >1.4 mm, >2 mm, >2.8 mm, >4 mm. Samples were poured onto the top sieve, which has the largest mesh openings. Each sieve below it in the column has smaller openings than the one above it (see sizes listed above). The receiver is located at the base. The column was placed on a mechanical shaker. The shaker shook the column. After shaking was complete, the material on each sieve was weighed. The weight of the sample on each sieve was then divided by the total weight to give a percentage retained on each sieve.The particle size distribution and the characteristic mean particle size, d50, were determined from the results of sieving analysis according to ISO 9276-2. Examples: Resin composition: The following components were mixed to form a charged heterophasic polypropylene composition. Table 1: Composition of heterophasic polypropylene charged to aeration. nRLznn / zznz / e / YiAi Component % by weight HECO 1 29.32 HECO 2 17.6 Component % by weight HECO 3 15.0 EP 1 6.0 Talc 17.0 CB 4.5 PE 8.0 PP 1.2 Epoxy resin 0.4 Erucamide 0.23 Nucleating agent NA21 0.2 Cyasorb UV 3808PP5 0.2 Irganox 1076 FD 0.15 Richfos 168 0.1 Creta 0.1 nRLznn / zznz / e / YiAi HECO 1: Commercial heterophasic propylene copolymer BJ400HP from Borealis AG, Austria, having an MFR2 (230 °C) melt flow index of 100 g / 10 min and a cold xylene solubles (XCS) content of 14% by weight. HECO 2: Commercial heterophasic propylene copolymer EF015AE from Borealis AG, Austria, having an MFR2 (230 °C) melt flow index of 18 g / 10 min and a cold xylene solubles (XCS) content of 31% by weight. HECO 3: Commercial heterophasic propylene copolymer ED007HP from Borealis AG, Austria, having a melt flow index MFR2 (230 °C) of 7 g / 10 min and a cold xylene solubles (XCS) content of 25% by weight. EP: Commercial ethylene-octene elastomeric copolymer Engage 8200 from Dow Chemical, USA, which has an MFR2 (190 °C) melt flow index of 5 g / 10 min and a density of 870 kg / m3. Talc: Jetfine 3 CA commercial talc from Imerys, UK. PE: Borealis BorPure™ MB7541 commercial high-density polyethylene that has an MFR2 (190 °C) melt flow index of 4 g / 10 min and a density of 954 kg / m3. PP: Borealis commercial propylene homopolymer HA001A-B1 having a melt flow index MFR2 (230 °C) of 0.6 g / 10 min. Epoxy resin: Commercial medium molecular weight bisphenol-based solid epoxy resin NPES-902 from Nan Ya Plastics Corporation, Taiwan. The combination was performed in a Coperion W&P ZSK40 twin-screw extruder at a temperature range of 220-240 °C followed by solidification of the resulting melt strand in a water bath and granulation. Comparative Example 1 (EC1): EC1 represents the resin composition described above, in which neither the individual components nor the final composition have been subjected to aeration. Comparative Example 2 (EC2): EC2 represents the resin composition described above, in which the final composition has been subjected to aeration after blending. Aeration was carried out in an insulated cylindrical silo with dimensions of 1.5 m3. The granules had an average particle size d50 of 3.5 mm (ISO 3310, evaluation according to ISO 9276-2). The granules were at room temperature (approximately 25 °C) before being subjected to aeration, i.e., no preheating stage was applied. The aeration process was carried out for 7 hours at a temperature of 140 °C. A gas flow rate of 260 m³ / h was used. This corresponds to a standardized gas flow rate of 2.6 Nm³ / kg. The granules were not mixed or agitated during the process, but were simply moved vertically through the silo at a rate of 100 kg / h. The process was carried out on a scale of 1000 kg, in a cylindrical silo of 1.5 m3. A relative flow rate of polypropylene composition granules of 100 kg / h was maintained throughout the aeration process. Inventive Example 1 (Eli): EI1 represents the resin composition described above, in which HECO 1, HECO 2 and HECO 3 have been individually aerated prior to the combination stage in which the described resin composition is mixed. The aeration conditions of the individual components are identical to those described above for EC2. The VOC and FOG values ​​obtained for HECO 1, HECO 2, HECO 3, and each final composition are given in Table 2. The values ​​in parentheses are the VOC and FOG values ​​for the individual components of un-aerated HECO. Table 2: Content of volatile and semi-volatile organic condensates of the resin components and final composition under different aeration regimes. nRLznn / zznz / e / viAi Example VOC (pg / g) FOG (pg / g) % VOC Reduction % FOG Reduction HECO 1 48 (197) 369 (630) 76% 41% HECO 2 56 (196) 377 (632) 71% 40% HECO 3 32 (131) 274 (394) 76% 30% EC1 205 545 - - EC2 42 283 80% 48% EI1 85 363 59% 33% nRLznn / zznz / e / YiAi As can be seen from the data shown in Table 2, while the reduction of VOC and FOG values ​​is greater for EC2 than for E11, the efficiency (i.e., the spatiotemporal performance) of E11 is improved. In the E11 process only approximately 62% of the composition has been aerated, while the reduction of VOC content is 73.6% as high as for EC2 (i.e., 59% / 80%) and the reduction of FOC content is 69.5% as effective. As discussed previously, this improved spatiotemporal efficiency has clear economic advantages, since aeration for relatively short periods requires less energy to supply heated gas. Additionally, less silo space is required to hold the polymer composition compared to longer aeration processes, where larger quantities of the polymer composition must be stored for extended periods. Further improvements could be expected if the aeration of each individual component were optimized separately, rather than the general conditions used for each resin.

Claims

1. A process for reducing the volatile and semi-volatile organic content (VOC and FOG values) of a heterophasic polypropylene composition, the heterophasic polypropylene composition comprising (i) at least 15 wt% of at least one first heterophasic polypropylene; (ii) less than 15 wt% of at least one elastomeric polyolefin; (iii) at least one filler; (iv) optionally polyethylene;and (v) optionally additional polyolefins below 100 pg / g (VOC, VDA 278 of October 2011) and below 390 pg / g (FOG, VDA 278 of October 2011), the process comprising the steps of (a) aerating the first heterophasic polypropylene through steps (a1) to (a5) wherein the polyolefin of said steps is the first heterophasic polypropylene; (a1) providing an aeration vessel having - at least one inlet for the aeration gas, - at least one outlet for the exhaust gas, - an inlet for a polyolefin at the top of the aeration vessel, - an outlet for the polyolefin at the bottom of the aeration vessel; wherein the polyolefin is present as a compact bed;a2) initiating a countercurrent flow of the polyolefin and the aeration gas a3) by - feeding the raw polyolefin showing a VOC value greater than 100 pg / g and a FOG value greater than 390 pg / g (VOC and FOG values ​​in accordance with VDA 278 of October 2011) into said aeration vessel from the top, - feeding the aeration gas into said aeration vessel through at least one inlet at the bottom; - extracting the exhaust gas through the exhaust gas outlet; a4) maintaining said aeration gas flow for an aeration time of less than 24 hours; a5) extracting the aerated polyolefin having a VOC value of less than 100 pg / g and a FOG value of less than 390 pg / g (VOC and FOG values ​​in accordance with VDA 278 of October 2011) through the outlet at the bottom of the aeration vessel;b) repeat steps a1) to a5) for the respective aeration of each additional polyolefin component that is present in an amount of at least 15% by weight with respect to the total weight of the heterophasic polypropylene composition, so that all polyolefin components that are individually present in an amount of at least 15% by weight with respect to the total weight of the heterophasic polypropylene composition are aerated;c) extruding the first extracted heterophasic polypropylene and any additional aerated polyolefin component with the at least one elastomeric polyolefin and the at least one filler and optional polyethylene and / or additional optional polyolefins if present to produce the heterophasic polypropylene composition having a VOC value below 100 pg / g (VDA 278 of October 2011) and a FOG value below 390 pg / g (VDA 278 of October 2011), wherein the at least one elastomeric polyolefin and the at least one filler are not aerated.

2. The process according to claim 1, wherein the first combined heterophasic polypropylene and any additional aerated polyolefin component constitute 50 to 90% by weight of the heterophasic polypropylene composition.

3. The process according to any one of the preceding claims, wherein the aeration gas is air.

4. The process according to any one of the preceding claims, wherein the process is continuous.

5. The process according to any one of the preceding claims, wherein the first crude heterophasic polypropylene and any additional polyolefin component to be aerated are provided in granule form and optionally the granules have a diameter D in the range of 2.5 mm up to 5 mm.

6. The process according to claim 6, wherein the granules are preheated before being added to the aeration vessel, such as preheated to 40 °C before being added to the aeration vessel.

7. The process according to any one of the preceding claims, wherein the aeration gas flow is maintained for an aeration time of less than 12 hours, preferably less than 10 hours, most preferably from 3 to 9 hours.

8. The process according to any one of the preceding claims, wherein the temperature of the aeration gas is from 100 °C to 140 °C, or from 110 °C to 135 °C, or from 115 °C to 130 °C.

9. The process according to any one of the preceding claims, whereby the exhaust gas is subjected to a purification stage and then recycled back to the inlet for the aeration gas.

10. The process according to any one of the preceding claims, wherein the exhaust gas optionally passes through a heat exchanger before being discharged to the atmosphere.

11. The process according to any one of the preceding claims, wherein the aeration vessel is cylindrical, conical, or cylindrical with a conical bottom portion.