Propylene copolymer composition

Abstract

The invention relates to a propylene copolymer composition comprising a propylene-ethylene copolymer, wherein the propylene-ethylene copolymer has a melt flow index in the range of 0.05 to 2.5 dg/min measured according to ISO1133 (2.16 kg/230° C.), wherein the propylene-ethylene copolymer is a unimodal propylene-ethylene copolymer and wherein a pipe prepared from the propylene copolymer composition according to ISO 1167-2 has a run time without failure of at least 2,500 h measured according to ISO1167-1 at a temperature of 95° C. and a hoop stress calculated according to ISO3213 of 4.2 MPa.

Claims

1. A propylene copolymer composition comprising at least 95 weight percent of a propylene-ethylene copolymer, wherein the propylene-ethylene copolymer has a melt flow index in the range of 0.05 to 2.5 dg/min measured according to ISO1133 (2.16 kg/230° C.), wherein the propylene-ethylene copolymer is a unimodal propylene-ethylene copolymer and wherein the composition is free of beta-nucleating agent and an extruded pipe prepared from the propylene copolymer composition according to ISO 1167-2 has a run time without failure of at least 2500 h measured according to ISO1167-1 at a temperature of 95° C. and a hoop stress calculated according to ISO3213 of 4.2 MPa.

2. The propylene copolymer composition according to claim 1, wherein the total amount of propylene-ethylene copolymer fractions that elute from a glass column filled with glass beads in the temperature range from 89 to 92° C. is at least 35 wt % based on the total propylene-ethylene copolymer present in the composition.

3. The propylene copolymer composition according to claim 1, wherein a pipe prepared from the propylene copolymer composition according to ISO1167-2 has a run time without ductile failure of at least 100 hours as measured according to ISO1167-1 at a temperature of 20° C. and a hoop stress calculated according to ISO3213 of 15.5 MPa.

4. The propylene copolymer composition according to claim 1, wherein the ethylene content in the propylene-ethylene copolymer is from 2.5 to 5.0 wt % based on the total propylene-ethylene copolymer.

5. The propylene copolymer composition according to claim 1, wherein the propylene-ethylene copolymer has a cold xylene soluble content of less than 10 wt %.

6. The propylene copolymer composition according to claim 1, wherein the propylene copolymer has a ratio between the melt flow index measured according to ISO1133 (2.16 kg/230° C.) and the melt flow index measured according to ISO1133 (10.0 kg/230° C.) of 0.010 to 0.10.

7. The propylene copolymer composition according to claim 1, wherein the propylene copolymer has a molecular weight distribution (Mw/Mn) of 6 to 12.

8. The propylene copolymer composition according to claim 1, wherein the propylene copolymer is prepared under the presence of a solid catalyst component for polymerization of olefins, comprising magnesium, titanium, a halogen and an electron donor, wherein said electron donor comprises at least one polyol ester compounds of the formula (I):
R.sub.1CO—O—CR.sub.3R.sub.4-A-CR.sub.5R.sub.6—O—CO—R.sub.2  (1) wherein, R.sub.1 and R.sub.2 groups, which may be identical or different, can be substituted or unsubstituted hydrocarbyl having 1 to 20 carbon atoms, R.sub.3-R.sub.6 groups, which may be identical or different, can be selected from the group consisting of hydrogen, halogen or substituted or unsubstituted hydrocarbyl having 1 to 20 carbon atoms, R.sub.1-R.sub.6 groups optionally contain one or more hetero-atoms replacing carbon, hydrogen atom or the both, said hetero-atom is selected from the group consisting of nitrogen, oxygen, sulfur, silicon, phosphorus and halogen atom, two or more of R.sub.3-R.sub.6 groups can be linked to form saturated or unsaturated monocyclic or polycyclic ring; A is a single bond or bivalent linking group with chain length between two free radicals being 1-10 atoms, wherein said bivalent linking group is selected from the group consisting of aliphatic, alicyclic and aromatic bivalent radicals, and can carry C.sub.1-C.sub.20 linear or branched substituents; one or more of carbon atom and/or hydrogen atom on the above-mentioned bivalent linking group and the substituents can be replaced by a hetero-atom selected from the group consisting of nitrogen, oxygen, sulfur, silicon, phosphorus, and halogen atom, and two or more said substituents on the linking group as well as above-mentioned R.sub.3-R.sub.6 groups can be linked to form saturated or unsaturated monocyclic or polycyclic ring.

9. The propylene copolymer composition according to claim 1, wherein the propylene-ethylene copolymer is prepared in gas phase polymerization process.

10. The propylene copolymer composition according to claim 1 further comprising additives.

11. The propylene copolymer composition according to claim 1, wherein an extruded pipe prepared from the propylene copolymer composition according to ISO 1167-2 has a run time without failure of at least 750 h measured according to ISO1167-1 at a temperature of 95° C. and a hoop stress calculated according to ISO3213 of 4.4 MPa, and/or an extruded pipe prepared from the propylene copolymer composition according to ISO 1167-2 has a run time without failure of at least 100 h measured according to ISO1167-1 at a temperature of 95° C. and a hoop stress calculated according to ISO3213 of 4.9 MPa.

12. A process for the preparation of the propylene copolymer composition according to claim 1, comprising contacting propylene and ethylene in a gas phase reactor.

13. A process for the production of a pipe comprising providing the copolymer composition according to claim 1 and forming it into the pipe.

14. A pipe comprising the propylene copolymer composition according to claim 1.

15. The pipe according to claim 14, wherein the pipe is prepared contains at least 95 wt % of the propylene-ethylene copolymer based on the pipe.

16. The process according to claim 12, wherein the contacting of the propylene and the ethylene is in one reactor.

17. The process according to claim 12, wherein the contacting of the propylene and the ethylene is in the presence of a solid catalyst component for polymerization of olefins, comprising magnesium, titanium, a halogen and an electron donor, wherein said electron donor comprises at least one polyol ester compounds of the formula (I):
R.sub.1CO—O—CR.sub.3R.sub.4-A-CR.sub.5R.sub.6—O—CO—R.sub.2  (1) wherein, R.sub.1 and R.sub.2 groups, which may be identical or different, can be substituted or unsubstituted hydrocarbyl having 1 to 20 carbon atoms, R.sub.3-R.sub.6 groups, which may be identical or different, can be selected from the group consisting of hydrogen, halogen or substituted or unsubstituted hydrocarbyl having 1 to 20 carbon atoms, R.sub.1-R.sub.6 groups optionally contain one or more hetero-atoms replacing carbon, hydrogen atom or the both, said hetero-atom is selected from the group consisting of nitrogen, oxygen, sulfur, silicon, phosphorus and halogen atom, two or more of R.sub.3-R.sub.6 groups can be linked to form saturated or unsaturated monocyclic or polycyclic ring; A is a single bond or bivalent linking group with chain length between two free radicals being 1-10 atoms, wherein said bivalent linking group is selected from the group consisting of aliphatic, alicyclic and aromatic bivalent radicals, and can carry C.sub.1-C.sub.20 linear or branched substituents; one or more of carbon atom and/or hydrogen atom on the above-mentioned bivalent linking group and the substituents can be replaced by a hetero-atom selected from the group consisting of nitrogen, oxygen, sulfur, silicon, phosphorus, and halogen atom, and two or more said substituents on the linking group as well as above-mentioned R.sub.3-R.sub.6 groups can be linked to form saturated or unsaturated monocyclic or polycyclic ring.

18. The composition of claim 1 comprising at least 96 weight percent of the propylene-ethylene copolymer.

Description

(1) The invention is now elucidated by way of the following examples, without however being limited thereto.

(2) Test Methods

(3) Comonomer Content (TC2)

(4) The comonomer content in the propylene copolymer is determined by .sup.13C NMR according to known procedures.

(5) MFI

(6) For purpose of the present invention, melt flow index is determined by measuring the melt flow rate, also called melt index, according to ISO1133 at a weight of 2.16 kg or 10.0 kg and a temperature of 230° C.

(7) Cold Xylene Solubles (XS)

(8) 1 gram of polymer and 100 ml of xylene are introduced in a glass flask equipped with a magnetic stirrer. The temperature is raised up to the boiling point of the solvent. The so obtained clear solution is then kept under reflux and stirring for further 15 min. Heating is stopped and the isolating plate between heating and flask is removed. Cooling takes places with stirring for 5 min. The closed flask is then kept for 30 min in a thermostatic water bath at 25° C. for 30 min. The so formed solid is filtered on filtering paper. 25 ml of the filtered liquid is poured in a previously weighed aluminium container, which is heated in a stove of 140° C. for at least 2 hours, under nitrogen flow and vacuum, to remove the solvent by evaporation. The container is then kept in an oven at 140° C. under vacuum until constant weight is obtained. The weight percentage of polymer soluble in xylene at room temperature is then calculated.

(9) Impact Strength (Izod Notched 23° C., // and L)

(10) For purpose of the present invention, impact strength is determined by measuring the Izod impact strength at 23° C. according to ISO 180 4A, Test geometry: 65*12.7*3.2 mm, notch 45° according to ISO 37/2, parallel (//) and perpendicular (L) orientation.

(11) Stiffness (Flexural Modulus 23° C., // and L)

(12) For purpose of the present invention, stiffness is determined by measuring the flexural modulus according to ASTM D790-10. Flexural modulus was determined on 3.2 mm thick specimens according to ISO37/2, parallel (//) and perpendicular (L) orientation.

(13) Internal Pressure Test:

(14) A pipe is prepared from the propylene copolymer composition according to ISO 1167-2. The measurement of the long-term hydrostatic strength of thermoplastics materials is carried out according to ISO 1167-1. The tests are carried out at described hoop stresses (measured according to ISO3213) and temperatures of 95° C. and 20° C.

(15) Molecular Weight Distribution (MWD)

(16) Mw (weight average molecular weight) and Mn (number average weight) of the propylene-ethylene copolymer are measured according to ASTM D6474-12 (Standard Test Method for Determining Molecular Weight Distribution and Molecular Weight Averages of Polyolefins by High Temperature Gel Permeation Chromatography).

(17) Fractionation:

(18) 1. Samples were fractionated using pTREF on aglass column filled with glass beads (as described in Bergstrom, J. Appl. Polym. Sci., 23, 1979, 163-171 & Wild, Polym Preprint Am Chem Soc 18, 1977, 182) Two gram of the samples were dissolved in xylene (4 hrs at 132° C.) and crystallized on a glass column with following steps: 2. Cooling step: the solution was cooled down to 120° C. by decreasing the temperature at a cooling rate of 1° C./min. 3. Crystallization step: the solution was cooled down to 20° C. by decreasing the temperature at a cooling rate of 1.5° C./hour. 4. Fractionation step: 1. <20° C. 2. 20-55° C. 3. 55-75° C. 4. 75-84° C. 5. 84-89° C. 6. 89-92° C. 7. 92-95° C. 8. 95-98° C. 9. 98-100° C.

(19) The polymers in the different fractions were precipitated in methanol and the dispersion was subsequently filtrated and dried under vacuum at 45° C. overnight. For each fraction, the amount and the molecular weight were measured.

EXPERIMENTS

(20) Preparation of Random Propylene Ethylene Copolymer

(21) Gas-phase polymerization of the propylene-ethylene copolymer was performed in a horizontal, stirred bed cylindrical reactor. The amount of ethylene in the copolymer (TC2) was controlled by adjusting the ratio between ethylene and propylene in the recycling gas in the reactor based on gas chromatography analysis. TC2 was measured using .sup.13C NMR according to known procedures.

(22) Examples 1-3 were prepared with catalyst as described in WO03/068828.

(23) Comparative example A is the propylene random copolymer RA130E, which is commercially available from BOREALIS.

(24) Comparative example B is the propylene random copolymer P9421, which is commercially available from SABIC.

(25) For the random polymerization the hydrogen concentration in the off gas was controlled to achieve the targeted melt flow rate.

(26) The propylene-ethylene copolymer powders as obtained were mixed with additives and melt-extruded to obtain granules.

(27) Various properties of the random propylene-ethylene copolymers and the compositions thus obtained were measured and are shown in Table 1.

(28) Preparation of Pipe

(29) The granules were used to extrude a pipe of 32*3.0 mm on a Reifenhauser S 50/30D/I- and S 50/30 D/II-Extruder according to ISO 1167-2.

(30) Hydrostatic pipe testing was carried out according to ISO 1167-1 at 95° C. and the hours after which the pipe failed under a hoop stress of either 4.2, 4.5 and 4.9 MPa (measured according to ISO3213) are mentioned in table 1.

(31) Hydrostatic pipe testing was carried out according to ISO 1167-2 at 20° C. and the hours after which the pipe failed with ductile failure under a hoop stress of 15.5 MPa (measured according to ISO3213) are mentioned in table 1.

(32) TABLE-US-00001 TABLE 1 Composition Ex 1 Ex 2 Ex 3 CEx A CEx B TC2 wt % 3.3 3.8 3.3 3.7 3.6 MFI (2.16 kg) granules dg/min 0.18 0.21 0.14 0.22 0.24 MFI (10 kg) granules dg/min 4.01 4.97 MFI 2.16/MFI 10 0.050 0.052 Mw/Mn 13.7 10.3 9.5 6.2 5.6 XS granules % 6.2 8.5 7 6.1 8.1 Izod notched 23° C. // [kJ/m2] 9.01 16.94 13.7 13.7 Izod notched 23° C. L [kJ/m2] 6.87 9.05 9.35 Flex mod 23 ° C. // [MPa] 1102 934 1049 1034 Flex mod 23 ° C. L [MPa] 1183 1032 1111 Pipe test at 95° C. time to failure 4.2 Mpa [h] 3541.5 3233.5 3992.5 2100 1043 time to failure 4.4 Mpa [h] 3123 2899.5 1400 715 time to failure 4.9 Mpa [h] 779.5 1452 1115.5 Pipe test at 20° C. time to ductile failure [h] 413.5 153 637 131.86 26 at 15.5 MPa

(33) It can be concluded from Table 1 that the time to failure is much longer for a pipe made from the composition according to the invention made in one reactor as compared to CEx B made in one reactor and at least similar compared to CEx A prepared in at least two reactors.

(34) The results of the fractionation are summarized in Table 2.

(35) TABLE-US-00002 TABLE 2 Ex 2 CEx A CEx B Glass column rel. rel. rel. temperature amount % amount % amount % (° C.) w/w Mw w/w Mw w/w Mw 89 22.6 730 22.1 705 10.5 430 92 21.9 1200 7.9 490 95 10.8 1700 22.5 890 8.4 490

(36) It can be seen that the total amount of propylene-ethylene copolymer fractions that elute from a glass column filled with glass beads in the temperature range from 89 to 92° C. is high in the composition of Ex 2 compared to CEx A and CEx B.

(37) Therefore, the invention also relates to a propylene copolymer composition, wherein the total amount of propylene-ethylene copolymer fractions that elute from a glass column filled with glass beads in the temperature range from 89 to 92° C. is at least 35 wt % based on the total propylene-ethylene copolymer present in the composition, preferably is at least 40 wt % based on the total propylene-ethylene copolymer present in the composition.

(38) Since the ethylene content (TC2) in each of the temperature fractions is similar, the relative amounts of the temperature fractions are indications of the distribution of C2 in the copolymer. It can therefore be concluded that the distribution of C2 in the copolymer is shifted more towards the lower temperature ranges in Ex 2 than CEx A and CEx B.