JACKET WITH IMPROVED PROPERTIES

Abstract

The present invention relates to a multimodal ethylene copolymer composition having a density of 920 to 949 kg/m.sup.3 and a flexural modulus, wherein said flexural modulus is following the equation: Flexural modulus [MPa]<21.35.Math.density [kg/m3]−19585 [1]. The multimodal ethylene copolymer composition according to the invention can be used in a highly flexible cable jacket, preferably a power cable jacket.

Claims

1. A multimodal ethylene copolymer composition having a density of 920 to 949 kg/m.sup.3, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2 (February 2007), and a flexural modulus, wherein said flexural modulus is measured according to the method of ISO 178 by using compression molded test specimens produced according to EN ISO 1872-2, and wherein numerical values of said flexural modulus, in MPa, and density, in kg/m.sup.3 follow the inequality:
Flexural modulus [MPa]<21.35.Math.density [kg/m.sup.3]−19585  [1], wherein the Flexural modulus is at least 32 MPa, wherein said ethylene copolymer is produced with a Ziegler-Natta catalyst with an internal organic compound having the formula (I) ##STR00004## wherein in the formula (I) R.sub.1 to R.sub.5 are same or different and can be hydrogen, a linear or branched C.sub.1 to C.sub.8-alkyl group, or a C.sub.3-C.sub.8-alkylene group, or two or more of R.sub.1 to R.sub.5 can form a ring, and the two oxygen-containing rings are individually saturated or partially unsaturated or unsaturated, wherein said multimodal ethylene copolymer composition has MFR.sub.2 measured according to ISO 1133 at 190° C. of 0.5 to 2 g/10 min, wherein said ethylene copolymer is produced in at least two polymerization stages, and wherein the Shore D (1 s) of the multimodal ethylene copolymer composition, as measured according to ISO868 on specimen molded according to EN ISO 1872-2, is at least 53.

2. The multimodal ethylene copolymer composition according to claim 1, wherein said multimodal ethylene copolymer composition comprises an ethylene copolymer comprising at least one alpha-olefin comonomer of C.sub.4 to C.sub.10.

3. The multimodal ethylene copolymer composition according to claim 2, wherein said ethylene copolymer comprises at least two alpha-olefin-comonomer(s).

4. The multimodal ethylene copolymer composition according to claim 3, wherein said ethylene copolymer comprises: at least a first alpha-olefin comonomer comprising 1-hexene; and a second alpha-olefin comonomer different from the first alpha-olefin comonomer.

5. The multimodal ethylene copolymer composition according to claim 4, wherein said ethylene copolymer comprises at least 1-butene and 1-hexenecomonomers.

6. (canceled)

7. The multimodal ethylene copolymer composition according to claim 1, wherein said multimodal ethylene copolymer composition has MFR.sub.2 measured according to ISO 1133 at 190° C. of 0.7 to 1.5 g/10 min.

8. The multimodal ethylene copolymer composition according to claim 1, wherein said multimodal ethylene copolymer composition has MFR.sub.5 measured according to ISO 1133 at 190° C. of 0.3 to 12 g/10 min.

9. The multimodal ethylene copolymer composition according to claim 1, wherein said multimodal ethylene copolymer composition has MFR.sub.21 measured according to ISO 1133 at 190° C. of 20 to 180 g/10 min.

10. (canceled)

11. The multimodal ethylene copolymer composition according to claim 1, wherein the flexural modulus is following the inequality:
Flexural modulus [MPa]<21.35.Math.density [kg/m.sup.3]−19610  [2].

12. The multimodal ethylene copolymer composition according to claim 1, wherein the density of said multimodal ethylene copolymer composition is 930 to 940 kg/m.sup.3.

13. (canceled)

14. The multimodal ethylene copolymer composition according to claim 1, wherein said multimodal ethylene copolymer composition further comprises carbon black.

15. A cable jacket comprising the multimodal ethylene copolymer composition according to claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0151] Test Methods

[0152] Melt Flow Rate

[0153] Melt flow rate (MFR) was determined according to ISO 1133 at 190° C. The load under which the measurement is conducted is given as a subscript. Thus, the MFR under the load of 2.16 kg is denoted as MFR.sub.2. The melt flow rate MFR.sub.21 is correspondingly determined at 190° C. under a load of 21.6 kg and MFR.sub.5 under a load of 5 kg.

[0154] Density

[0155] Density of the polymer was measured according to ISO 1183-1:2004 Method A on compression moulded specimen prepared according to EN ISO 1872-2 (February 2007) and is given in kg/m.sup.3.

[0156] Reactor Gas Composition

[0157] Reactor gas composition in a slurry reactor can be measured, as is well known in the art, from the flash gas after the reactor by using on-line gas chromatography, as disclosed, for instance, in WO-A-1996035936.

[0158] Reactor gas composition in a gas phase reactor can be analyzed from the circulation gas by using on-line chromatography, as it is well known in the art.

[0159] The instruments are calibrated, as it is known in the art, with calibration gas mixtures having a known composition which is close to that of the gas mixture present in the polymerization process.

[0160] Flexural Test (Modulus)

[0161] Flexural modulus reflects the flexibility of a material. The higher the flexural modulus, the lower the flexibility of a material, i.e. the material is more difficult to deform under a given load.

[0162] The flexural test was carried out according to the method of ISO 178 by using compression molded test specimens produced according to EN ISO 1872-2.

[0163] A rectangular specimen of size 80×4×10 mm was placed between two supports. The specimen was then pressed down with a loading edge placed in the middle of the specimen with the speed of 2 mm/min. In this case, only the flexural modulus was investigated and thus the flexural strain was measured between 0.05% and 0.25% on which the flexural modulus was calculated.

[0164] Tensile Test (Strength)

[0165] Tensile test was measured according to ISO 527.

[0166] Crosshead speed for testing the tensile strength and elongations was 50 mm/min.

[0167] Test specimen produced as described in EN ISO 1872-2, specimen type: 5A to ISO 527-2 were used.

[0168] Shore D

[0169] Shore D (1 s) is determined according to ISO868 on moulded specimen with a thickness of 4 mm. The shore hardness is determined after 1 sec after the pressure foot is in firm contact with the test specimen. The specimen was moulded according to EN ISO1872-2.

[0170] Quantification of Microstructure by NMR Spectroscopy

[0171] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymers. Quantitative .sup.13C{.sup.1H} NMR spectra recorded in the molten-state using a Bruker Advance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimized 7 mm magic-angle spinning (MAS) probehead at 150° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4 kHz. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification {klimke06, parkinson07, castignolles09}. Standard single-pulse excitation was employed utilizing the NOE at short recycle delays {pollard04, klimke06} and the RS-HEPT decoupling scheme {fillip05,griffin07}. A total of 1024 (1 k) transients were acquired per spectra.

[0172] Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts are internally referenced to the bulk methylene signal (δ+) at 30.00 ppm {randall89}.

[0173] The amount of ethylene was quantified using the integral of the methylene (δ+) sites at 30.00 ppm accounting for the number of reporting sites per monomer:

E=I.sub.δ+/2

[0174] The presence of isolated comonomer units is corrected for based on the number of isolated comonomer units present:

Etotal=E+(3.Math.B+2.Math.H)/2

[0175] where B and H are defined for their respective comonomers. Correction for consecutive and non-consecutive comonomer incorporation, when present, is undertaken in a similar way.

[0176] Characteristic signals corresponding to the incorporation of 1-butene were observed and the comonomer fraction was calculated as the fraction of 1-butene in the polymer with respect to all monomer in the polymer:

fBtotal=Btotal/(Etotal+Btotal+Htotal)

[0177] The amount isolated 1-butene incorporated in EEBEE sequences was quantified using the integral of the *B2 sites at 38.3 ppm accounting for the number of reporting sites per comonomer:

B=I.sub.*B2

[0178] The amount of consecutively incorporated 1-butene in EEBBEE sequences was quantified using the integral of the ααB2B2 site at 39.4 ppm accounting for the number of reporting sites per comonomer:

BB=2.Math.I.sub.ααB2B2

[0179] The amount of non-consecutively incorporated 1-butene in EEBEBEE sequences was quantified using the integral of the ββB2B2 site at 24.7 ppm accounting for the number of reporting sites per comonomer:

[0180] Due to the overlap of *B2 and *ββB2B2 sites of isolated (EEBEE) and non-consecutively incorporated (EEBEBEE) 1-butene respectively the total amount of isolated 1-butene incorporation is corrected based on the amount of non-consecutive 1-butene present:

B=I.sub.*B2−2.Math.I.sub.ββB2B2

[0181] The total 1-butene content was calculated based on the sum of isolated, consecutively and non-consecutively incorporated 1-butene:

Btotal=B+BB+BEB

[0182] The total mole fraction of 1-butene in the polymer was then calculated as:

fB=Btotal/(Etotal+Btotal+Htotal)

[0183] Characteristic signals corresponding to the incorporation of 1-hexene were observed and the comonomer fraction calculated as the fraction of 1-hexene in the polymer with respect to all monomer in the polymer:

fHtotal=Htotal/(Etotal+Btotal+Htotal)

[0184] The amount isolated 1-hexene incorporated in EEHEE sequences was quantified using the integral of the *B4 sites at 39.9 ppm accounting for the number of reporting sites per comonomer:

H=I.sub.*B4

[0185] The amount of consecutively incorporated 1-hexene in EEHHEE sequences was quantified using the integral of the ααB4B4 site at 40.5 ppm accounting for the number of reporting sites per comonomer:

HH=2.Math.I.sub.ααB4B4

[0186] The amount of non-consecutively incorporated 1-hexene in EEHEHEE sequences was quantified using the integral of the ββB4B4 site at 24.7 ppm accounting for the number of reporting sites per comonomer:

HEH=2.Math.I.sub.ββB4B4

[0187] The total mole fraction of 1-hexene in the polymer was then calculated as:

fH=Htotal/(Etotal+Btotal+Htotal)

[0188] The mole percent comonomer incorporation is calculated from the mole fraction:

B [mol %]=100.Math.fB

H [mol %]=100.Math.fH

[0189] The weight percent comonomer incorporation is calculated from the mole fraction:

B [wt %]=100.Math.(fB.Math.56.11)/((fB.Math.56.11)+(fH.Math.84.16)+((1−(fB+fH)).Math.28.05))

H [wt %]=100.Math.(fH.Math.84.16)/((fB.Math.56.11)+(fH.Math.84.16)+((1−(fB+fH)).Math.28.05))

REFERENCES

[0190] klimke06 [0191] Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006; 207:382.

[0192] parkinson07 [0193] Parkinson, M., Klimke, K., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2007; 208:2128.

[0194] pollard04 [0195] Pollard, M., Klimke, K., Graf, R., Spiess, H. W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004; 37:813.

[0196] filip05 [0197] Filip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005, 176, 239

[0198] griffin07 [0199] Griffin, J. M., Tripon, C., Samoson, A., Filip, C., and Brown, S. P., Mag. Res. in Chem. 2007 45, S1, S198

[0200] castignolles09 [0201] Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373

[0202] busico01 [0203] Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443

[0204] busico97 [0205] Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromoleucles 30 (1997) 6251

[0206] zhou07 [0207] Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225

[0208] busico07 [0209] Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128

[0210] resconi00 [0211] Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253

[0212] Materials

[0213] Catalyst 1

[0214] Complex Preparation

[0215] Toluene (87 kg) was added into a 100 liter reactor. Then Bomag A, provided by Chemtura, (45.5 kg, 20 wt % butyloctyl magnesium in heptane) was added to the reactor. Then 2-ethyl-1-hexanol (161 kg, 99.8 wt %) was introduced into the reactor at a flow rate of 24-40 kg/h. The molar ratio between BOMAG-A and 2-ethyl-1-hexanol was 1:1.83.

[0216] Solid Catalyst Component Preparation

[0217] 10 275 kg silica (ES747JR of Crossfield, having average particle size of 20 μm) activated at 600° C. in nitrogen was charged into a catalyst preparation reactor. Then, 411 kg 20% EADC (2.0 mmol/g silica) diluted in 555 litres pentane was added into the reactor at ambient temperature during one hour. The temperature was then increased to 35° C. while stirring the treated silica for one hour. The silica was dried at 50° C. for 8.5 hours. Then 655 kg of the complex prepared as described above (2 mmol Mg/g silica) was added at 23° C. during ten minutes. 86 kg pentane was added into the reactor at 22° C. during ten minutes. The slurry was stirred for 8 hours at 50° C. Finally, 52 kg TiCl.sub.4 was added during 0.5 hours at 45° C. The slurry was stirred at 40° C. for five hours. The catalyst was then dried by purging with nitrogen.

[0218] Catalyst 2

[0219] Preparation of Pre-Treated Support Material

[0220] A jacketed 160 dm.sup.3 stainless steel reactor equipped with a helical mixing element was pressurized with N.sub.2 to 2.0 barg and depressurized down to 0.2 barg until the O.sub.2 level was less than 3 ppm. The vessel was then charged with heptane (20.5 kg) and 2,2-di(tetrahydrofuryl)propane (0.512 kg; 79 mol; DTHFP). The obtained mixture was stirred for 20 min at 40 rpm. The MgCl.sub.2.3EtOH carrier (6.5 kg; DTHFP/Mg=0.1 mol/mol; 27.2 mol of Mg; Mg 10.18 wt %, d10=9.5 μm, d50=17.3 μm and d90=28.5 μm, granular shaped) was added to the reactor with stirring. This suspension was cooled to approximately −20° C. and 33 wt % solution of triethylaluminum (29.4 kg, 85.0 mol of Al; Al/EtOH=1.0 mol/mol) in heptane was added in aliquots during 2.5 h time while keeping the temperature below 10° C. After the TEA addition, the reaction mixture was gradually heated to 80° C. over a period of 2.4 h and kept at this temperature for additional 20 min at 40 rpm. The suspension was allowed to settle for 10 min, and the mother liquor was removed through a 10 μm filter net in the bottom of the reactor during 15 min. The vessel was charged with warm toluene (43 kg) and then stirred at 40 rpm for 38 min at 55 to 70° C. The suspension was allowed to settle for 10 min at 50 to 55° C. and the liquid removed through a 10 μm filter net in the bottom of the reactor during 15 min.

[0221] Catalyst Preparation

[0222] The vessel containing the pre-treated support material was charged with toluene (43 kg) and then cooled to approximately 30° C. Neat TiCl.sub.4 (5.17 kg, 27.5 mol; Ti/Mg=1.0 mol/mol) was added. The obtained suspension was heated to approximately 90° C. over a period of 2 h and kept at this temperature for one additional hour with stirring at 40 rpm. The suspension was allowed to settle for 10 min at approximately 90° C. and the mother liquor was removed through a 10 μm filter net in the bottom of the reactor during 15 min. The obtained solid material was washed twice with toluene (43 kg each) at ˜90° C. and once with heptane (34 kg) at ˜40° C. All three of these washing steps used the same sequence of events: addition of preheated (90 or 40° C.) solvent, then stirring at 40 rpm for 30 min, allowing the solid to settle for 10 min, and then removal of liquid through a 10 μm filter net in the bottom of the reactor during 15 min.

[0223] The obtained catalyst was mixed with 20 kg of white oil and dried 4 h at 40-50° C. with nitrogen flow (2 kg/h) and vacuum (−1 barg). The catalyst was taken out from the reactor and the reactor was flushed with another 20 kg of oil and taken out to the same drum. The dry catalyst yield was 3.60 kg (82.2% based on Mg).

[0224] Polymerization

Inventive Examples

[0225] A loop reactor having a volume of 50 dm.sup.3 was operated at a temperature of 60° C. and a pressure of 58 bar. Into the reactor were fed ethylene, 1-butene, propane diluent and hydrogen so that the feed rate of ethylene was 4.0 kg/h, feed rate of 1-butene was 50 g/h, feed rate of hydrogen was 10 g/h and feed rate of propane was 52 kg/h. Also, 3 g/h of a solid polymerization catalyst component produced as described above in chapter “Catalyst Preparation” was introduced into the reactor together with triethylaluminum cocatalyst so that the molar ratio of Al/Ti was about 15. The estimated production rate was 3.8 kg/h.

[0226] A stream of slurry from the reactor was withdrawn intermittently and directed into a loop reactor having a volume of 350 dm.sup.3, which was operated at 85° C. temperature and 56 bar pressure. Into the reactor was further added a fresh propane feed of 116 kg/h, ethylene and hydrogen so that the ethylene content in the fluid reaction mixture was 3.8 mol % and the molar ratio of hydrogen to ethylene was 500 mol/kmol. The ethylene copolymer withdrawn from the reactor had MFR.sub.2 of 300 g/10 min and density of 972 kg/m.sup.3. The production rate was 38 kg/h.

[0227] The slurry was withdrawn from the loop reactor intermittently and directed to a flash vessel operated at a temperature of 50° C. and a pressure of 3 bar. From there the polymer was directed to a fluidized bed gas phase reactor operated at a pressure of 20 bar and a temperature of 75° C. Additional ethylene, 1-hexene comonomer, nitrogen as inert gas and hydrogen were added so that the ethylene content in the fluid reaction mixture was 20 mol %, the ratio of hydrogen to ethylene was 150 mol/kmol and the molar ratio of 1-hexene to ethylene was 210 mol/kmol. The polymer production rate in the gas phase reactor was 55 kg/h and thus the total polymer withdrawal rate from the gas phase reactor was about 97 kg/h. The polymer had a melt flow rate MFR.sub.5 of 3.0 g/10 min and a density of 920 kg/m.sup.3. The production split (wt % prepolymer/wt % 1st stage component/wt % 2nd stage component) was 4/44/52.

[0228] The polymer powder was compounded and pelletized with 0.2 wt % Irganox B 141, 6.6 wt % carbon black masterbatch based on LDPE (MFR.sub.190° C./2.16 kg=2 g/10 min), containing ˜40% N220-type carbon black, 0.1 wt % Irganox B 225 FF and 0.05 wt % calcium stearate.

[0229] The procedure of Inventive Example 1 was repeated with the conditions as shown in Table 1.

TABLE-US-00001 TABLE 1 Pilot production data Comparative Inventive Inventive Example CE Example IE1 Example IE2 Catalyst type Catalyst 1 Catalyst 2 Catalyst 2 Pre-poly A1 Temperature ° C. 70 60 60 A1 Ethylene feed (kg/h) 2 4 4 A1 1-butene feed (kg/h) 0.108 0.05 0.05 A1 Hydrogen feed (g/h) 4.7 9.9 9.9 A1 Production rate (kg/h) 1.9 3.8 3.8 Loop (A2) A2 Temperature (° C.) 85 85 85 A2 H2/C2 ratio (mol/kmol) 267.2 521 506.9 A2 C4/C2 ratio (mol/kmol) 600 677 689.4 A2 Density 948.3 949.2 949.1 A2 MFR.sub.2 (g/10 min) 323 320 304 GPR (A3) A3 Temperature (° C.) 75 75 75 A3 H2/C2 ratio (mol/kmol) 30 142 152 A3 C6/C2 ratio (mol/kmol) 212 214 A3 C4/C2 ratio (mol/kmol) 668 A3 split wt % 55.5 56.6 56.9 A3 Density (kg/m.sup.3) 922.3 921.3 919.9 A3 MFR.sub.2 (g/10 min) 0.83 0.76 0.83 A3 MFR.sub.5 (g/10 min) 3.1 3.0 3.0 A3 MFR.sub.21 (g/10 min) 65 62 64 Mixer powder Mixer density (kg/m.sup.3) 923.1 925.3 924.2 Mixer MFR.sub.2 (g/10 min) 0.72 0.72 na Mixer MFR.sub.5 (g/10 min) 2.9 2.9 2.9 Mixer MFR.sub.21 (g/10 min) 58 62 50

[0230] IE1 and IE2 are made with catalyst 2. CE is made with Catalyst 1. CE is produced with similar process properties and has a significantly higher flexibility in relation to IE1 and IE2.

[0231] IE1, IE2 and CE are produced as described above in pilot scale compared to a commercial reference LE8707, which is available from Borealis AG, produced in a large scale plant. The comparative example CE is made to be as close as possible to the commercial reference in selection of process parameter and selection of catalyst. It can be seen that the pilot scale material (CE) is significantly less flexible compared to the commercial product. This indicated that the invention will work even better in large scale plants.

[0232] Table 2 compares the IE1, IE2 and CE with LE8707. Both IE1 and IE2 have lower flexural modulus than LE8707 but comparable hardness.

TABLE-US-00002 TABLE 2 Summary of analytics and tests of the final material LE8707 (compar- Compar- ative ative Inventive Inventive com- example Example Example Unit mercial) (CE) 1 (IE1) 2 (IE2) Flexural MPa 400 473 348 337 modulus Final kg/m.sup.3 936 936.1 937.4 934.7 Density MFR.sub.2 g/10 min 0.85 0.72 0.71 0.81 MFR.sub.5 g/10 min na 2.7 2.7 3.1 MFR.sub.21 g/10 min 65 54 69 62 FRR 75 76 96 77 21.6/2.16 Tensile % 800 729 730 740 strain at break Tensile MPa 30 22.8 26.9 27.5 stress at break Shore D (1 s) 54 50.1 54.4 56.8 C4 content Mol % 3.6 3.9 0.5 0.6 C6 content Mol % 0 0 2.6 2.8

[0233] As can be seen in the Table 2, comparative examples and inventive examples have similar densities. Surprisingly, it can be seen that the flexibility of the inventive examples is considerably higher than the comparative example, while Shore D hardness has increased. Other properties are in similar range as the comparative example.

[0234] FIG. 1 shows flexural modulus as a function of density. As may be seen in FIG. 1, the inventive examples IE1 and IE2 follows the equation as described above, i.e.

Flexural modulus [MPa]<21.35.Math.density [kg/m.sup.3]−19585

[0235] Although the present invention has been described with reference to various embodiments, those skilled in the art will recognize that changes may be made without departing from the scope of the invention. It is intended that the detailed description be regarded as illustrative, and that the appended claims including all the equivalents are intended to define the scope of the invention.