AERATED POLYPROPYELENE COMPOSITIONS EXHIBITING SPECIFIC EMISSION

Abstract

A polypropylene composition comprising oligomers having a semi-volatile organic condensable (FOG,VDA 278 October 2011), content of 50 μg/g to about 400 μg/g of the total polypropylene composition, and volatile organic compounds (VOC,VDA 278 October 2011) in an amount of less than 80 μg/g of the total polypropylene composition, wherein the weight ratio of said oligomers versus said volatiles is more than about 5.0, wherein the polypropylene composition has an MFR.sub.2 (ISO 1133, 230° C., 2.16 kg) of 10 g/10 min or higher, wherein the polypropylene composition a flexural modulus (ISO 178 on injection moulded specimens of 80×10×4 mm prepared in accordance with ISO 294-1:1996) of from 1000 to 2000 MPa, and wherein the total quantity of slip agent is at least 500 ppm.

Claims

1. A propylene composition comprising: semi-volatile organic condensable oligomers (FOG,VDA 278 October 2011) in an amount of 50 μg/g to about 400 μg/g of the total polypropylene composition, and volatile organic compounds (VOC,VDA 278 October 2011) in an amount of less than 80 μg/g of the total polypropylene composition, wherein the weight ratio of said semi-volatile organic condensable oligomers versus said volatile organic compounds is more than about 5.0, wherein the polypropylene composition has an MFR.sub.2 (ISO 1133, 230° C., 2.16 kg) of 10 g/10_min or higher, wherein the polypropylene composition has a flexural modulus (ISO 178 on injection moulded specimens of 80×10×4 mm prepared in accordance with ISO 294-1:1996) of from 1000 to 6000 MPa, and wherein the total quantity of slip agent is at least 500 ppm.

2. The polypropylene composition according to claim 1, obtainable by i) blending: polypropylene, filler, slip agent, optional HDPE, optional plastomer, and optional pigment, in the presence of additives to obtain a blend, and further ii) subjecting the blend to a 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, c) by: feeding the raw polypropylene composition having a volatile organic compound content (VOC, VDA 278 October 2011) of greater than about 150 μg/g and a semi-volatile organic condensable content of greater than about 350 μg/g (FOG,VDA 278 October 2011), into said aeration vessel from the top, feeding the aeration gas into said aeration vessel via the at least one inlet at the bottom; 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 96 hours, wherein, the temperature of the gas is from 100° C. to 140° C., and wherein, the Reynolds number of the gas flow is from 5 to 150, whereby the Reynolds number for the flow of aeration gas through the packed bed is defined by formula (I):
Re=(ρv.sub.sD)/μ  (I) where: ρ is the density of the aeration gas at the temperature used (kg/m.sup.3), μ is the kinematic viscosity of the aeration gas at the temperature used (kg/ms), v.sub.s is the superficial velocity, defined as Q/A where Q is the volume flow rate of the aeration gas, (m.sup.3/s) and A is the cross sectional area (m.sup.2), and D is the diameter (m) of the particles, and wherein no further clip agent is added to the composition after step d).

3-9. (canceled)

10. The polypropylene composition according to claim 1, wherein the polypropylene composition has a puncture energy of from 35 to 45 J.

11. The polypropylene component composition according to claim 1, wherein the filler is selected from the group consisting of talc, glass, and mixtures thereof.

12. (canceled)

13. The polypropylene composition according to claim 1, wherein the propylene composition comprises semi-volatile organic condensable oligomers (FOG,VDA 278 October 2011) in an amount of 50 μg/g to about 170 μg/g of the total polypropylene composition, and volatile organic compounds (VOC,VDA 278 October 2011) in an amount of 20 μg/g or less of the total polypropylene composition.

14. The polypropylene composition according to claim 1, wherein the slip agent is a fatty acid amide.

15. The polypropylene composition according to claim 1, wherein the slip agent is erucamide or oleamide.

16. The polypropylene composition according to claim 1, wherein the VDA 277 value is less than 1.

17. The polypropylene composition according to claim 1, wherein the fogging gravimetric is less than 1.1, and/or wherein the VDA 270 value is 3 or less.

18. The polypropylene composition according to claim 1, wherein the polypropylene composition has an MFR.sub.2 (ISO 1133, 230° C., 2.16 kg) of from 10 to 25 g/10 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0256] FIG. 1: Ratio FOG/VOCs based on VDA 278 October 2011 before vs. after the aeration process.

EXPERIMENTAL PART

[0257] The following Examples are included to demonstrate certain aspects and embodiments of the invention as described in the claims. It should be appreciated by those of skill in the art, however, that the following description is illustrative only and should not be taken in any way as a restriction of the invention.

Test Methods

[0258] Sample Preparation

[0259] VOC values, FOG values and TVOC values were measured as described below, after sample preparation consisting of injection moulding plaques in the acc. EN ISO 19069-2:2016. These plaques were packed in aluminium-composite foils immediately after production and the foils were sealed.

[0260] For the thermodesorption analysis according to VDA 278 (October 2011) the samples were stored uncovered at room temperature (23° C. max.) for 7 days directly before the commencement of the analysis.

[0261] Regarding the VDA 277 (January 1995) measurements, no additional uncovered storage or other conditioning took place. Instead, the injection moulded plaques were cut and ground in a Retsch SM-2000 mill.

[0262] In both cases (VDA 277 and VDA 278), the production date of the injection moulded plaques, the time when the sample arrived in the lab as well as the analysis date were recorded.

[0263] VOC and FOC acc VDA278

[0264] VOC:

[0265] is determined according to VDA 278 October 2011 from injection moulded plaques. VDA 278 October 2011, Thermal Desorption Analysis of Organic Emissions for the Characterization of Non-Metallic Materials for Automobiles, VDA Verband der Automobilindustrie. According to the VDA 278 October 2011 the VOC value is defined as “the total of the readily volatile to medium volatile substances. It is calculated as toluene equivalent. The method described in this Recommendation allows substances in the boiling/elution range up to n-Pentacosane (C25) to be determined and analyzed.”

[0266] FOG:

[0267] is determined according to VDA 278 October 2011 from injection moulded plaques. According to the VDA 278 October 2011 the FOG value is defined as “the total of substances with low volatility which elute from the retention time of n-Tetradecane (inclusive). It is calculated as hexadecane equivalent. Substances in the boiling range of n-Alkanes “C.sub.14” to “C.sub.32” are determined and analyzed.”

[0268] Total Emission, TVOC:

[0269] The total emission of the polypropylene composition was determined by VDA 277 January 1995 from pellets.

[0270] Fogging:

[0271] Fogging was measured according to DIN 75201:2011-11, method B (gravimetric method) on compression-moulded specimens (diameter 80 mm +/−1 mm, thickness <1 cm) cut out from an injection-moulded plate. With this method the mass of fogging condensate on aluminium foil in mg by means weighing of foil before and after the fogging test is determined. The term “fogging” refers to a fraction of volatile substances condensed on glass parts as e.g. the windscreen of a vehicle.

[0272] Diameter D:

[0273] A sieve analysis according to ISO 3310 was performed. The sieve analysis involved a nested column of sieves with wire mesh screen 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, >4mm. The samples were poured into the top sieve which has the largest screen openings. Each lower sieve in the column has smaller openings than the one above (see sizes indicated above). At the base is the receiver. The column was placed in a mechanical shaker. The shaker shook the column. After the shaking was completed the material on each sieve was weighed. The weight of the sample of each sieve was then divided by the total weight to give a percentage retained on each sieve. The particle size distribution and the characteristic median particle size d50 was determined from the results of the sieve analysis according to ISO 9276-2.

[0274] Melt Flow Rate (MFR.sub.2):

[0275] The melt flow rates were measured with a load of 2.16 kg (MFR.sub.2) at 230° C. The melt flow rate is the quantity of polymer in grams which the test apparatus standardized to ISO 1133 extrudes within 10 minutes at a temperature of 230° C. under a load of 2.16 kg.

[0276] Xylene Cold Soluble Fraction (XCS Wt %):

[0277] The xylene cold soluble fraction (XCS) is determined at 23° C. according to ISO 6427.

[0278] NMR-Spectroscopy Measurements:

Quantification of Microstructure by NMR Spectroscopy

[0279] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution of the polymers. Quantitative .sup.13C{.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 10 mm extended temperature probehead at 125° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2) along with chromium-(III)-acetylacetonate (Cr(acac).sub.3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatory oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6 k) transients were acquired per spectra. Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed Cheng, H. N., Macromolecules 17 (1984), 1950).

[0280] With characteristic signals corresponding to 2,1 erythro regio defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio defects on determined properties was required. Characteristic signals corresponding to other types of regio defects were not observed.

[0281] The comonomer fraction was quantified using the method of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157) through integration of multiple signals across the whole spectral region in the .sup.13C{.sup.1H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

[0282] For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et. al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:

E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

[0283] Through the use of this set of sites the corresponding integral equation becomes:

E=0.5(I.sub.H+I.sub.G+0.5(I.sub.C+I.sub.D))

[0284] using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolute propylene content were not modified.

[0285] The mole percent comonomer incorporation was calculated from the mole fraction:

E[mol %]=100*fE

[0286] The weight percent comonomer incorporation was calculated from the mole fraction:

E[wt %]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

[0287] The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

[0288] Polymer-Puncture Plaque-Instrumented:

[0289] Puncture energy is determined in the instrumented falling weight test according to ISO 6603-2 using injection moulded plaques of 60×60×1 mm and a test speed of 2.2 m/s, clamped, lubricated striker with 20 mm diameter. The reported puncture energy results from an integral of the failure energy curve measured at (60×60×1 mm).

[0290] Flexural Modulus:

[0291] The flexural modulus was determined in 3-point-bending according to ISO 178 on injection molded specimens of 80×10×4 mm prepared in accordance with ISO 294-1:1996.

VDA 270:

[0292] VDA 270 is a determination of the odour characteristics of trim-materials in motor vehicles. VDA 270 was determined according to the standards used by the “Verband der Deutsche industrie,” 1992. In general, the material is warmed in a sealed vessel (with or without de-ionised water) for a period of time. The vessels are then removed from the warmed environment and at least 3 human subjects then rate the odour of a particular polymeric material on a scale of 1 to 6, according to the categories described below:

[0293] 1: imperceptible

[0294] 2: noticeable, not disturbing

[0295] 3: clearly noticeable, but not yet disturbing

[0296] 4: disturbing

[0297] 5: strongly disturbing

[0298] 6: unbearable

Experiments

[0299]

TABLE-US-00001 TABLE 1 Properties of the base resins used in the compositions used in Example 1. C2 (ethylene MFR.sub.2 content) Base resin Type (g/10 min) XS (wt-%) (wt-%).sup.2 Resin 1 Heterophasic 100 13 6.5 polypropylene copolymer (HECO) Resin 2 RTPO.sup.1 (RAHECO) 5.5 25 6.5 Resin 3 RTPO.sup.1 (RAHECO) 18 31 20 Resin 4 Homopolymer 75 — — (polypropylene) Resin 5 Heterophasic 20 18 8 polypropylene copolymer (HECO) .sup.1Random thermoplastic olefin .sup.2Determined by .sup.13C-NMR spectroscopy

TABLE-US-00002 TABLE 2 The composition of each of the polypropylene compositions used in Example 1 A B C D E Base Resin 1 46 29.5 — — 32.0 resin Resin 2 21 15 10 — 15 Resin 3 — 19.5 40.5 28 4.4 Resin 4 — — 48.5 — Resin 5 — 25.0 — HDPE 6 8 8 — 10 Elastomer.sup.1 7 4 — — 11 Filler Talc filler 10 17 7 — 20.5 Glass filler — — — 20 — Carbon 7.5 4.5 6 0.5 3 black/other carbon Total 97.5 97.5 96.5 97 96 Slip agent Properties.sup.2 Tm (° C.) 165 166 166 165 165 MFR (g/10 20 17 13 12 14 min) Puncture 42 39 39 6 38 energy 23° C., 4.4 m/s, 3 mm (J) Flexural 1700 1800 1400 4200 1900 modulus (MPa) Values are given in weight percent and rounded to the nearest 0.5%. .sup.1An ethylene-propylene elastomer. .sup.2Properties of the raw polypropylene compositions before aeration.

EXAMPLE 1 (Ex1)

[0300] Batches of pelletized polypropylene compositions, corresponding to the materials A, B, C, D and E as defined in Table 2 respectively, were subjected to aeration. Aeration was carried out in an insulated cylindrically shaped silo with dimensions of 1.5 m.sup.3.

[0301] The pellets had a median particle size d50 of 3.5 mm (ISO 3310, evaluation according to ISO 9276-2). The pellets were at room temperature (ca. 25° C.) before being subject to aeration i.e. a pre-heating step was not applied.

[0302] The aeration process was carried out for 7.5 hours at a temperature of 140° C. A gas flow rate of 260 m.sup.3/h was used. The pellets were not mixed or agitated during the process and instead simply moved vertically through the silo at a speed of 100 kg/hour.

[0303] The process was carried out on a 1000 kg scale. In a cylindrical silo of 1.5 m.sup.3. A relative flow rate of polypropylene composition pellets of 100 kg/hr was maintained throughout the aeration process.

[0304] The aeration process was carried out continuously for 7 hours.

[0305] The VOC, FOG, VDA 277 and Fogging gravimetric obtained for each grade before and after the aeration step is given in Table 4.

TABLE-US-00003 TABLE 3 Summary of the airflow characteristics used in the present experiments Units Value in the current experiments density of the fluid kg/m.sup.3 0.85 (gas)/ kinematic viscosity of kg/m s 2.35 × 10.sup.−5 the fluid (gas)/μ superficial velocity/v.sub.s m/s 0.16 Diameter of the m  0.0035 particles (method as described above)

[0306] The Reynolds number can be calculated using the formula:

Re=(ρv.sub.sD)/μ

where: [0307] :density of the aeration gas at the temperature used (kg/m.sup.3) [0308] μ: kinematic viscosity of the aeration gas at the temperature used (kg/m s) [0309] v.sub.s: superficial velocity, defined as Q/A where Q is the volume flow rate of the aeration gas, (m.sup.3/s) and A is the cross sectional area (m.sup.2) [0310] D: d50 diameter (m) of the particles (using sieve analysis according to ISO3310 and evaluation according to ISO9276-2)

[0311] The Reynolds number for the gas flow used in the process of example 1 was 20.

TABLE-US-00004 TABLE 4 VOC, FOG, VDA 277, Fogging gravimetric, VDA 270 and ratio of FOG/VOC for polymers A, B, C, D and E. VDA 270 - Odour VDA278, VDA278, Fogging 5 pax, Polymer VOC* FOG* VDA277 gravimetric median FOG/VOC A Before 232 460 45 1.28 3 2 aeration After 12 161 1 0.52 13 aeration B Before 188 400 41 1.26 4 2 aeration After 16 235 0 1.08 4 15 aeration C Before 245 464 45 0.85 2 aeration After 14 150 0 0.32 11 aeration D Before 246 467 31 1.06 3 2 aeration After 5 114 0 0.45 3 23 aeration E Before 190 326 35 0.77 5 2 aeration After 15 149 3 0.33 10 aeration

[0312] VOC and FOG values were measured after 7 days according to VDA 278, VDA277 and fogging gravimetric were measured immediately

[0313] Surprisingly, the total quantity of slip agent after aeration was above 500 ppm for all polymers A to E.

TABLE-US-00005 TABLE 5 Properties of polypropylene compositions A, B and C following aeration Melting Percentage change in point, Tm Puncture energy 23° C., puncture energy before Polymer (° C.) 4.4 m/s, 3 mm (J) and after aeration (%) A 165 42 0 B 166 40 2.5 C 166 39 0 D 166 6 0 E 165 39 3