	US 12,281,218 B2
	Reduction in VOC and FOG values of polypropylene grades by aeration
Girish Suresh Galgali, Linz (AT); Luca Boragno, Linz (AT); Andreas Fuchs, Linz (AT); Jürgen Huber, Linz (AT); and Stefanie Engleder, Linz (AT)
Assigned to BOREALIS AG, Vienna (AT)
Appl. No. 17/289,629
Filed by BOREALIS AG, Vienna (AT)
PCT Filed Oct. 30, 2019, PCT No. PCT/EP2019/079690 § 371(c)(1), (2) Date Apr. 28, 2021, PCT Pub. No. WO2020/089308, PCT Pub. Date May 7, 2020.
Claims priority of application No. 18203757 (EP), filed on Oct. 31, 2018.
Prior Publication US 2021/0395504 A1, Dec. 23, 2021
This patent is subject to a terminal disclaimer.
Int. Cl. C08L 23/14 (2006.01); B01D 19/00 (2006.01); C08F 6/00 (2006.01); C08L 23/16 (2006.01); B29B 9/16 (2006.01)

CPC C08L 23/14 (2013.01) [B01D 19/0005 (2013.01); C08F 6/005 (2013.01); C08L 23/16 (2013.01); B29B 2009/168 (2013.01); C08L 2205/025 (2013.01); C08L 2205/035 (2013.01); C08L 2207/062 (2013.01)]

13 Claims

1. A process for reducing the volatile and semi-volatile organic compounds (VOC and FOG values) of a polypropylene composition to below 20 μg/g (VOC, VDA 278 October 2011) and below 250 μg/g (FOG, VDA 278 October 2011), the polypropylene composition including a polypropylene homopolymer and/or a polypropylene random copolymer,

the process comprising the steps of:

a) providing an aeration vessel having:

at least one inlet for aeration gas,

at least one outlet for exhaust gas,

an inlet for a raw polypropylene composition at the top of the aeration vessel,

an outlet for the polypropylene composition at the bottom of the aeration vessel;

wherein the polypropylene composition is present as a packed bed;

b) initiating a counter-current flow of the polypropylene composition and aeration gas, wherein the aeration gas is nitrogen or air or mixtures thereof;

c) by

feeding particles of the raw polypropylene composition showing a VOC value of greater than about 150 μg/g and an FOG value of greater than about 350 μg/g (VOC and FOG values according to VDA 278 October 2011), into said aeration vessel from the top, the polypropylene homopolymer and/or the polypropylene random copolymer having a melting point (Tm) of greater than 150° C., a melt flow rate MFR₂(230° C.) of 4 to 160 g/10 min, and a xylene soluble fraction having a melt flow rate MFR₂from 10 to 40 g/10 min prior to aeration, wherein the particles of the raw polypropylene composition are in pellet form and the pellets have a diameter D in the range of from 2.8 to 4.0 mm, wherein a polypropylene composition weight flow through the aeration vessel is from 70 to 170 kg/h referenced to an aeration vessel with a volume of 1.5 m³;

feeding the aeration gas into said aeration vessel via the at least one inlet at the bottom, wherein a total volumetric airflow used is from 2 Nm³/kg to 4 Nm³/kg, the total volumetric airflow being the volume of gas flowing into the aeration vessel per hour referenced to the polypropylene composition weight flow;

withdrawing the exhaust gas via the outlet for exhaust gas;

withdrawing the aerated polypropylene composition via the outlet at the bottom of the aeration vessel;

d) maintaining said aeration gas flow for an aeration time of from 3 to 9 hours,

wherein, the temperature of the aeration gas is from 100° C. to 150° C., and wherein a Reynolds number (Re) of the gas flow is from 15 to 50, wherein the Reynolds number for the flow of aeration gas through the packed bed is defined by formula (I):

Re=(ρ·v_s·D)/μ (I)

where:

ρ is the density of the aeration gas at the temperature used (kg/m³),

μ is the kinematic viscosity of the aeration gas at the temperature used (kg/m s),

v_sis the superficial velocity, defined as Q/A where Q is the volume flow rate of the aeration gas, (m³/s) and A is a cross sectional area (m²) of the aeration vessel, and

D is a diameter (m) of the particles,

wherein the polypropylene composition is not agitated during aeration and the aeration is not a fluidized bed process.