Propylene copolymer composition with improved long-term mechanical properties

Abstract

Propylene-ethylene random copolymers with improved long-term mechanical properties, especially improved impact strength retention, their manufacture as well as their use, e.g. for the production of moulded articles, particularly injection moulded articles, such as thin-walled plastic containers for packaging.

Claims

1. A propylene-ethylene random copolymer having: (i) a melt flow rate MFR.sub.2 (according to ISO 1133, 230 C., 2.16 kg) in the range of 50 to 120 g/10 min, (ii) a total ethylene comonomer content of 3.0 to 9.0 mol % (iii) a content of an orthorhombic gamma-crystal phase 100.K of less than 45% as determined by wide-angle X-ray diffraction (WAXS) on a 60602 mm.sup.3 injection moulded test specimen and comprising: 0.0001 to 1.0 wt %, based on the total weight of the propylene-ethylene random copolymer, of a polymeric -nucleating agent (pNA).

2. The propylene-ethylene random copolymer according to claim 1, comprising two propylene copolymer fractions: a) a first propylene copolymer fraction (PP-COPO-1) having an ethylene comonomer content of at most 3.5 mol %, and b) a second propylene copolymer fraction (PP-COPO-2), said first propylene copolymer fraction (PP-COPO-1) having a higher MFR.sub.2 and/or a lower ethylene comonomer content than said second propylene copolymer fraction (PP-COPO-2).

3. The propylene-ethylene copolymer according to claim 2, wherein the first propylene copolymer fraction (PP-COPO-1) has an ethylene comonomer content of at least 1.0 mol % and at most 3.5 mol % and the second propylene copolymer fraction (PP-COPO-2) has an ethylene comonomer content in the range of 2.0 mol % to at most 11.0 mol %, whereby the first propylene copolymer fraction (PP-COPO-1) has an ethylene comonomer content below that of the second propylene copolymer fraction (PP-COPO-2).

4. The propylene-ethylene copolymer according to claim 2, wherein the first propylene copolymer fraction (PP-COPO-1) has a melt flow rate MFR.sub.2 (230 C.) in the range of 50.0 to 150 g/10 min and the second propylene copolymer fraction (PP-COPO-2) has a melt flow rate MFR.sub.2 (230 C.) in the range of 40.0 to 120 g/10 min, whereby the MFR.sub.2 of the second propylene copolymer fraction (PP-COPO-2) is lower than the MFR.sub.2 of the first propylene copolymer fraction (PP-COPO-1).

5. The propylene-ethylene copolymer according to-claim 2, wherein the second propylene copolymer fraction (PP-COPO-2) has an ethylene comonomer content which is higher than the ethylene comonomer content of the first propylene copolymer fraction (PP-COPO-1) and has an MFR.sub.2 which is lower than the MFR.sub.2 of the first propylene copolymer fraction (PP-COPO-1).

6. The propylene-ethylene copolymer according to-claim 1, wherein the polymeric -nucleating agent is a polymerized vinyl compound of formula (I): ##STR00002## wherein R.sub.1 and R.sub.2 together form a 5 or 6 membered saturated or unsaturated or aromatic ring or they stand independently for a lower alkyl comprising 1 to 4 carbon atoms.

7. The propylene-ethylene copolymer according to claim 6, whereby the polymerized vinyl compound is selected from the group consisting of vinyl cycloalkanes.

8. The propylene-ethylene copolymer according to-claim 1, wherein the propylene-ethylene copolymers is prepared in the presence of: a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a non-phthalic compound; b) optionally a co-catalyst (Co), and c) optionally an external donor (ED).

9. The propylene-ethylene copolymer according to claim 8, wherein: a) the internal donor (ID) is selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and derivatives or mixtures thereof; and b) a molar-ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is 5 to 45.

10. The propylene-ethylene copolymer according to claim 1, wherein the propylene-ethylene copolymer is produced in a sequential polymerization process, comprising a prepolymerization reactor (PPR) and at least one reactor (R1) or at least two reactors (R1) and (R2), whereby in the prepolymerization reactor a vinyl compound is first polymerized with a catalyst system, comprising a Ziegler-Natta catalyst component, a cocatalyst and optional external donor, a reaction mixture of a polymer of the vinyl compound and the catalyst system is then introduced in a first polymerization reactor (R1), whereby in the first polymerization reactor (R1) a first propylene copolymer fraction (PP-COPO-1) is produced and subsequently transferred into a second polymerization reactor (R2), in the second polymerization reactor (R2) a second propylene copolymer fraction (PP-COPO-2) is produced in the presence of the first propylene copolymer fraction (PP-COPO-1).

11. A molded article, comprising a propylene-ethylene copolymer according to claim 1.

12. A thin wall packaging made by injection molding, comprising a propylene-ethylene copolymer according to claim 1.

13. A molded article according to claim 11, having: a tensile modulus (measured according to ISO 527) measured after 96 hours of storage at +231 C. and 50% relative humidity (standard conditions) of at least 1050 MPa and tensile modulus (measured according to ISO 527) measured after 1440 hours of storage under standard conditions of at least 1100 MPa and simultaneously having a puncture energy (measured according to ISO 6603-2; 60602 mm.sup.3 specimens) measured after 96 hours of storage under standard conditions of at least 23 J, and measured after 1440 hours of storage under standard conditions of at least 19 J.

Description

EXPERIMENTAL PART

A) Measuring Methods

(1) The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

(2) Calculation of comonomer content of the second propylene copolymer fraction (PP-COPO-2):

(3) $\begin{array}{cc}\frac{C\left(\mathrm{PP}\right)-w\left(\mathrm{PP}1\right)C\left(\mathrm{PP}1\right)}{w\left(\mathrm{PP}2\right)}=C\left(\mathrm{PP}2\right)& \left(I\right)\end{array}$
wherein w(PP1) is the weight fraction [in wt %] of the first propylene copolymer fraction (PP-COPO-1), w(PP2) is the weight fraction [in wt %] of second propylene copolymer fraction (PP-COPO-2, C(PP1) is the comonomer content [in mol %] of the first propylene copolymer fraction (PP-COPO-1), C(PP) is the comonomer content [in mol %] of the propylene-ethylene copolymer, C(PP2) is the calculated comonomer content [in mol %] of the second propylene copolymer fraction (PP-COPO-2).

(4) Calculation of melt flow rate MFR.sub.2 (230 C.) of the second propylene copolymer fraction (PP-COPO-2):

(5) $\begin{array}{cc}\mathrm{MFR}\left(PP2\right)={10}^{\left[\frac{\log \left(\mathrm{MFR}\left(\mathrm{PP}\right)\right)-w\left(\mathrm{PP}1\right)\log \left(\mathrm{MFR}\left(\mathrm{PP}1\right)\right)}{w\left(\mathrm{PP}2\right)}\right]}& \left(\mathrm{III}\right)\end{array}$
wherein w(PP1) is the weight fraction [in wt %] of the first propylene copolymer fraction (PP-COPO-1), w(PP2) is the weight fraction [in wt %] of second propylene copolymer fraction (PP-COPO-2), MFR(PP1) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the first propylene copolymer fraction (PP-COPO-1), MFR(PP) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the propylene-ethylene copolymer, MFR(PP2) is the calculated melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the second propylene copolymer fraction (PP2-COPO-2).

(6) MFR.sub.2 (230 C.) is measured according to ISO 1133 (230 C., 2.16 kg load).

(7) Quantification of Microstructure by NMR Spectroscopy

(8) 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 rotatary 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.

(9) 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).

(10) 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.

(11) 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.

(12) 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(S+S+S+0.5(S+S))

(13) 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))
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.

(14) The mole percent comonomer incorporation was calculated from the mole fraction:
E[mol %]=100*fE

(15) The weight percent comonomer incorporation was calculated from the mole fraction:
E[wt %]=100*(fE*28.06)/((fE*28.06)+((1fE)*42.08))

(16) 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.

(17) The relative content of isolated to block ethylene incorporation was calculated from the triad sequence distribution using the following relationship (equation (I)):

(18) $\begin{array}{cc}I\left(E\right)=\frac{\mathrm{fPEP}}{\left(\mathrm{fEEE}+\mathrm{fPEE}+\mathrm{fPEP}\right)}100& \left(I\right)\end{array}$
wherein
I(E) is the relative content of isolated to block ethylene sequences [in %];
fPEP is the mol fraction of propylene/ethylene/propylene sequences (PEP) in the sample;
fPEE is the mol fraction of propylene/ethylene/ethylene sequences (PEE) and of ethylene/ethylene/propylene sequences (EEP) in the sample;
fEEE is the mol fraction of ethylene/ethylene/ethylene sequences (EEE) in the sample

(19) The xylene solubles (XCS, wt %): Content of xylene cold solubles (XCS) is determined at 25 C. according ISO 16152; first edition; 2005 Jul. 1

(20) ICP Analysis (Al, Mg, Ti)

(21) The elemental analysis of a catalyst was performed by taking a solid sample of mass, M, cooling over dry ice. Samples were diluted up to a known volume, V, by dissolving in nitric acid (HNO.sub.3, 65%, 5% of V) and freshly de-ionized (DI) water (5% of V). The solution was further diluted with DI water up to the final volume, V, and left to stabilize for two hours.

(22) The analysis was run at room temperature using a Thermo Elemental iCAP 6300 Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) which was calibrated using a blank (a solution of 5% HNO.sub.3), and standards of 0.5 ppm, 1 ppm, 10 ppm, 50 ppm, 100 ppm and 300 ppm of Al, Mg and Ti in solutions of 5% HNO.sub.3.

(23) Immediately before analysis the calibration is resloped using the blank and 100 ppm standard, a quality control sample (20 ppm Al, Mg and Ti in a solution of 5% HNO.sub.3 in DI water) is run to confirm the reslope. The QC sample is also run after every 5.sup.th sample and at the end of a scheduled analysis set.

(24) The content of Mg was monitored using the 285.213 nm line and the content for Ti using 336.121 nm line. The content of aluminium was monitored via the 167.079 nm line, when Al concentration in ICP sample was between 0-10 ppm (calibrated only to 100 ppm) and via the 396.152 nm line for Al concentrations above 10 ppm.

(25) The reported values are an average of three successive aliquots taken from the same sample and are related back to the original catalyst by inputting the original mass of sample and the dilution volume into the software.

(26) The amount of residual VCH in the catalyst/oil mixture was analysed with a gas chromatograph. Toluene was used as internal standard.

(27) Tensile test: The tensile modulus was measured at 23 C. according to ISO 527-1 (cross head speed 1 mm/min) using injection moulded specimens moulded at 180 C. or 200 C. according to ISO 527-2(1B), produced according to EN ISO 1873-2 (dog 10 bone shape, 4 mm thickness).

(28) The tensile modulus for the examples was measured after 96 h and 1440 hours of storage.

(29) Puncture energy was determined in the instrumental falling weight (IFW) test according to ISO 6603-2 using injection moulded plaques of 60602 mm and a test speed of 2.2 m/s. Puncture energy reported results from an integral of the failure energy curve measured at +23 C.

(30) The puncture energy for the examples was measured after 96 h and 1440 hours of storage

(31) Wide-Angle X-Ray Scattering (WAXS)

(32) Samples prepared for WAXS were prepared in the same way as for the puncture energy measurement.

(33) The determination of crystallinity and of polymorphic composition was performed in reflection geometry using a Bruker D8 Discover with GADDS x-ray diffractometer operating with the following settings: x-ray generator: 30 kV and 20 mA; .sub.1=6 & .sub.2=13; sample-detector distance: 20 cm; beam size (collimator): 500 m; and duration/scan: 300 seconds. 3 measurements have been performed on each sample. Intensity vs. 2 curves between 2=10 and 2=32.5 were obtained by integrating the 2-dimensional spectra. The quantification of intensity vs. 2 curves were then performed as follows:

(34) Intensity vs. 2 curve was acquired with the same measurement settings on an amorphous iPP sample, which was prepared by solvent extraction. An amorphous halo was obtained by smoothing the intensity vs. 2 curve. The amorphous halo has been subtracted from each intensity vs. 2 curve obtained on actual samples and this results in the crystalline curve.

(35) The crystallinity index X.sub.c is defined with the area under the crystalline curve and the original curve using the method proposed by Challa et al. (Makromol. Chem. vol. 56 (1962), pages 169-178) as:

(36) $X_c=\frac{\mathrm{Area}\mathrm{under}\mathrm{crystalline}\mathrm{curve}}{\mathrm{Area}\mathrm{under}\mathrm{original}\mathrm{spectrum}}100.$

(37) In a two-phase crystalline system (containing - and -modifications), the amount of -modification within the crystalline phase B was calculated using the method proposed by Turner-Jones et al. (Makromol. Chem. Vol. 75 (1964), pages 134-158) as:

(38) $B=\frac{{.Math.}^{}\left(300\right)}{{.Math.}^{}\left(110\right)+{.Math.}^{}\left(040\right)+{.Math.}^{}\left(130\right)+{.Math.}^{}\left(300\right)},$
where, I.sup.(300) is the intensity of (300) peak, I.sup. (110) is the intensity of (110) peak, I.sup.(040) is the intensity of (040) peak and I.sup.(130) is the intensity of (130) peak obtained after subtracting the amorphous halo.

(39) In a two-phase crystalline system (containing - and -modifications), the amount of -modification within the crystalline phase G (i.e. K) was calculated using the method developed by Pae (J. Polym. Sci., Part A2, vol. 6 (1968), pages 657-663) as:

(40) $G=\frac{{.Math.}^Y\left(117\right)}{{.Math.}^{}\left(130\right)+{.Math.}^Y\left(117\right)},$
where, I.sup.(130) is the intensity of (130) peak and I.sup.(117) is the intensity of (117) peak obtained after subtracting a base line joining the base of these peaks.

B) Examples

Inventive Examples IE1 and IE2

(41) Used Chemicals:

(42) 20% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et), BEM), provided by Chemtura

(43) 2-ethylhexanol, provided by Amphochem

(44) 3-Butoxy-2-propanol(DOWANOL PnB), provided by Dow

(45) bis(2-ethylhexyl)citraconate, provided by SynphaBase

(46) TiCl.sub.4, provided by Millenium Chemicals

(47) Toluene, provided by Aspokem

(48) Viscoplex 1-254, provided by Evonik

(49) Heptane, provided by Chevron

(50) Preparation of a Mg Complex

(51) First a magnesium alkoxide solution was prepared by adding, with stirring (70 rpm), into 1 1 kg of a 20 wt-% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et), BEM), a mixture of 4.7 kg of 2-ethylhexanol and 1.2 kg of butoxypropanol in a 20 l stainless steel reactor. During the addition the reactor contents were maintained below 45 C. After addition was completed, mixing (70 rpm) of the reaction mixture was continued at 60 C. for 30 minutes. After cooling to room temperature 2.3 kg g of the donor bis(2-ethylhexyl)citraconate was added to the Mg-alkoxide solution keeping temperature below 25 C. Mixing was continued for 15 minutes under stirring (70 rpm)

(52) Preparation of Solid Catalyst Component

(53) 20.3 kg of TiCl.sub.4 and 1.1 kg of toluene were added into a 20 l stainless steel reactor. Under 350 rpm mixing and keeping the temperature at 0 C., 14.5 kg of the Mg complex prepared in example 1 was added during 1.5 hours. 1.7 l of Viscoplex 1-254 and 7.5 kg of heptane were added and after 1 hour mixing at 0 C. the temperature of the formed emulsion was raised to 90 C. within 1 hour. After 30 minutes mixing was stopped catalyst droplets were solidified and the formed catalyst particles were allowed to settle. After settling (1 hour), the supernatant liquid was siphoned away.

(54) Then the catalyst particles were washed with 45 kg of toluene at 90 C. for 20 minutes followed by two heptane washes (30 kg, 15 min). During the first heptane wash the temperature was decreased to 50 C. and during the second wash to room temperature.

(55) VCH Modification of the Catalyst

(56) 41 liters of mineral oil (Paraffinum Liquidum PL68) were added to the prepolymerization reactor of a Borstar pilot plant followed by 1.79 kg of triethyl aluminium (TEAL) and 0.79 kg of dicyclopentyl dimethoxy silane (donor D) under inert conditions at room temperature. Afterwards 5.5 kg of the catalyst prepared as described above for the inventive Examples was added, followed by 5.55 kg of vinylcyclohexane (VCH).

Comparative Example 1 (CE1)

(57) The catalyst used in the polymerization processes of the comparative example (CE1) was the catalyst of the example section of WO 2010009827 A1 (see pages 30 and 31) along with triethyl-aluminium (TEAL) as co-catalyst and dicyclopentyl dimethoxysilane (D-donor) as donor.

(58) This catalyst was not modified with VCH.

(59) The polymerization was done in a Borstar pilot plant with a prepolymerization reactor, a loop reactor and a gas phase reactor (1.sup.st GPR) for IE1; IE2 and CE1

(60) The polymerization conditions are indicated in table 1.

(61) TABLE-US-00001 TABLE 1 Preparation of the Examples IE1 IE2 CE1 Prepolymerization Temperature ( C.) [ C.] 32 32 30 Ethylene feed [kg/h] 0.23 0.21 0.40 Residence time [h] 0.36 0.36 0.34 Donor [] D D D Donor feed [g/tC3] 51.9 51.4 42.0 Cocatalyst feed [g/tC3] 180 180. 120 Loop (PP-COPO-1) Temperature [ C.] 70 70 80 Residence time [h] 0.42 0.42 0.25 C2/C3 [mol/kmol] 11.0 9.65 13.5 H2/C3 [mol/kmol] 3.4 3.1 2.8 MFR [g/10 min] 111.1 85.8 70 C2 [mol %] 1.4 1.3 1.4 XCS [wt %] 4.6 4.2 4.0 split [%] 51 46 46 1st GPR/(PP-COPO-2) Temperature [ C.] 80 80 90 Residence time [h] 2.0 2.1 1.2 C2/C3 [mol/kmol] 40.4 36.0 46.5 H2/C3 [mol/kmol] 141.0 143.0 150.0 MFR [g/10 min] 91.0 76.4 70 C2 [mol %] 4.2 4.0 4.0 XCS [wt %] n.d. 9.1 6.0 split [%] 49 54 54 n.d. not determined

(62) All polymer powders were compounded in a co-rotating twin-screw extruder Coperion ZSK 57 at 220 C. with 0.2 wt % of Irganox B225 (1:1-blend of Irganox 1010 (Pentaerythrityl-tetrakis(3-(3,5-di-tert.butyl-4-hydroxytoluyl)-propionate and tris (2,4-di-t-butylphenyl) phosphate) phosphite) of BASF AG, Germany) and 0.05 wt % calcium stearate and the below described nucleating agents.

(63) The material of the comparative example CE1 was nucleated with 0.2 wt % of the sorbitol M3988, commercially available from Millad, based on the total weight of the propylene-ethylene copolymer.

(64) The properties of the nucleated copolymers are shown in Table 2:

(65) TABLE-US-00002 TABLE 2 properties of nucleated copolymers Example IE1 IE2 CE1 MFR2 (230 C., [g/10 91 71 68 2.16 kg) min] C2 total (NMR) [mol %] 6.2 6.5 5.6 100.K/WAXS [%] 35 37 52 Tensile modulus after [MPa] 1063 1080 1121 96 h Tensile modulus after [MPa] 1157 1175 1215 1440 h Puncture energy after [J] 27.8 27.2 25.5 96 h Puncture energy after [J] 22.2 21.8 17.2 1440 h n-PEP.sup.1) [%] 65 62 73 EEE [mol %] 0.91 0.83 0.67 PEE [mol %] 1.38 1.66 1.01 PEP [mol %] 4.31 4.08 4.73 PPP [mol %] 86.34 84.90 86.96 EPP [mol %] 8.20 8.84 7.90 EPE [mol %] 0.25 0.31 0.05 ${}^{1)}I\left(E\right)=\frac{\mathrm{fPEP}}{\left(\mathrm{fEEE}+\mathrm{fPEE}+\mathrm{fPEP}\right)}100\left(I\right)$

(66) From Figure 1 it can be seen that the polymers of IE1 and IE2 (in-reactor nucleated) have a clearly slower trend of puncture energy decrease than the polymer of the comparative example CE1 (post-reactor nucleated.