RAISED TEMPERATURE RESISTANT PIPES COMPRISING AN ETHYLENE-BASED POLYMER

Abstract

The present invention relates to a pipe comprising an ethylene-based polymer, wherein the ethylene-based polymer: ⋅ comprises ≥0.10 mol % of units derived from 1-hexene, with regard to the total molar quantity of polymeric units of the ethylene-based polymer; ⋅ has an M.sub.w/M.sub.n as determined in accordance with ASTM D6474 (2012) of ≥2.5 and ≤4.0, preferably of ≥2.5 and ≤3.4; ⋅ has a density as determined in accordance with ASTM D792 (2008) of ≥925 and ≤945 kg/m.sup.3; and ⋅ in the molecular weight range of log(M.sub.w) between 4.0 and 5.5, has a comonomer branch content of between 2 and 15 comonomer-derived branches per 1000 carbon atoms in the polymer, as determined via .sup.13C NMR. Such pipe provides a desirably high long-term strength, as demonstrated by its high strain hardening modulus, as well as desirably high impact strength, as demonstrated by its high Charpy impact strength. Further, such pipe may be compliant with the PE-RT requirements of ISO 22391-1 (2009). For example, such pipe may be used for containing water at temperatures in the range of 40° C. to 80°.

Claims

1. Pipe comprising an ethylene-based polymer, wherein the ethylene-based polymer: comprises ≥0.10 mol %, of units derived from 1-hexene, with regard to the total molar quantity of polymeric units of the ethylene-based polymer; has a molecular weight distribution M.sub.w/M.sub.N as determined in accordance with ASTM D6474 (2012) of ≥2.5 and ≤4.0; has a density as determined in accordance with ASTM D792 (2008) of ≥925 and ≤945 kg/m.sup.3; and in the molecular weight range of log(M.sub.w) between 4.0 and 5.5 has a comonomer branch content of between 2 and 15 comonomer-derived branches per 1000 carbon atoms in the polymer, as determined via .sup.13C NMR.

2. Pipe according to claim 1, wherein the ethylene-based polymer has a comonomer incorporation ratio of ≥1.50, wherein the comonomer incorporation ratio is defined as the ratio between the quantity of comonomer-derived branches per 1000 carbon atoms in the polymer at log(M.sub.w)=5.5 and the quantity of comonomer-derived branches per 1000 carbon atoms in the polymer at log (M.sub.w)=4.0, as determined via .sup.13C NMR.

3. Pipe according to claim 1, wherein the ethylene-based polymer comprises ≥95.0 mol % of units derived from ethylene, with regard to the total molar quantity of polymeric units of the ethylene-based polymer.

4. Pipe according to claim 1, wherein the ethylene-based polymer has a melt mass-flow rate of ≥0.1 and ≤5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190° C. under a load of 2.16 kg.

5. Pipe according to claim 1, wherein the ethylene-based polymer has a melt mass-flow rate of ≥0.5 and ≤3.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190° C. under a load of 5.0 kg.

6. Pipe according to claim 1, wherein the ethylene-based polymer has a melt mass-flow rate of ≥5.0 and ≤25.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190° C. under a load of 21.6 kg.

7. Pipe according to claim 1, wherein the pipe is a potable cold water pipe, a potable hot water pipe, a pipe for an underfloor heating system, or a pipe for a solar heat collection system.

8. Pipe according to claim 1, wherein the pipe has the value ‘Pass’ for PERT-I when tested according to the requirements of ISO 22391-1 (2009).

9. Pipe according to claim 1 wherein the ethylene-based polymer is produced in a gas-phase polymerisation process operated in a fluidised bed reactor.

10. Pipe according to claim 1, wherein the ethylene-based polymer is produced in the presence of a supported single-site catalyst comprising a metallocene complex.

11. Process for production of an ethylene-based polymer used in the pipe according to claim 1, wherein the process comprises polymerisation of a reaction mixture comprising ethylene and 1-hexene, in the presence of a supported single-site catalyst, wherein the single-site catalyst comprises a metallocene complex according to formula I: ##STR00002## wherein: R2 is a bridging moiety containing at least one sp2 hybridised carbon atom; each R4, R4′, R7 and R7′ are hydrogen or moieties comprising 1-10 carbon atoms, wherein each R4, R4′, R7 and R7′ are the same; each R5, R5′, R6 and R6′ are hydrogen or moieties comprising 1-10 carbon atoms, wherein each R5, R5′, R6 and R6′ are the same; and Z is a moiety selected from ZrX.sub.2, HfX.sub.2, or TiX.sub.2, wherein X is selected from the group of halogens, alkyls, aryls and aralkyls.

12. Process according to claim 11, wherein the bridging moiety R2 is a substituted or unsubstituted methylene- or a 1,2-phenylene or 2,2′-biphenylene moiety.

13. Process according to claim 11, wherein the process is a gas-phase polymerisation process operated in a fluidised bed reactor.

14. Process according to claim 11, wherein the polymerisation of the reaction mixture comprising ethylene and 1-hexene is conducted in the presence of the supported single-site catalyst, and cocatalyst, and a continuity aid agent, wherein the continuity aid agent preferably is a product obtained by reaction of a compound of the formula A1(R1)(R2)(R3) with a compound of the formula N(R4)(R5)(R6), wherein: R1 is hydrogen or a hydrocarbon group having 1-30 carbon atoms; R2 and R3 are the same or different and each a hydrocarbon group having 1-30 carbon atoms; R4 is hydrogen, a functional group with at least one active hydrogen, or a moiety having 1-30 carbon atoms; R5 is hydrogen or a moiety having 1-30 carbon atoms; and R6 is a moiety having 1-30 carbon atoms.

15. A method comprising exposing the pipe according to claim 1 to a hot water system wherein the pipe has improved raised temperature resistance in accordance with ISO 22391-1 (2009).

16. Pipe according to claim 1, wherein the ethylene-based polymer comprises ≥1.00 and ≤2.00 mol %, of units derived from 1-hexene, with regard to the total molar quantity of polymeric units of the ethylene-based polymer.

Description

[0067] The invention will now be illustrated by the following non-limiting examples.

Materials

[0068]

TABLE-US-00001 Metallocene [2,2′-bis(2-indenyl)biphenyl]zirconium dichloride, CAS reg. nr. 312968-31-3, obtainable from Innovasynth Technologies Support Silica 955, obtainable from W.R. Grace & Co Cocatalyst Methyl aluminoxane (MAO), CAS reg. nr. 29429-58-1, obtainable from W.R. Grace & Co Cocatalyst aid Triisobutyl aluminium (TIBAL), CAS reg. nr. 100-99-2, obtainable from Sigma-Aldrich Antistatic agent Cyclohexyl amine, CAS reg. nr. 108-91-8 Continuity aid agent Composition comprising 2 wt % of a blend of the cocatalyst aid and the antistatic agent (at molar ratio 2.85:1) diluted in iso-pentane

Catalyst Production

[0069] The support was pre-dehydrated at 600° C. for 4 hours. 3 g of the pre-dehydrated support was charged into a 100 ml two-neck Schlenk flask in a glovebox under nitrogen atmosphere, followed by addition of 15 ml of toluene. After shaking, a suspension was obtained. 0.052 g of the metallocene was activated by mixing it with 6.3 ml of a 10 wt % solution of the cocatalyst in toluene in a 25 ml vial at room temperature for 10 min in the glovebox, also under nitrogen atmosphere. The activated metallocene was transferred into the suspension. The mixture was heated to 70° C. and maintained at that temperature for 1 hour. Subsequently, the product was dried at 70° C. under vacuum to obtain the supported catalyst, which was isolated as free-flowing powder. The supported catalyst contained 0.24 wt % of Zr and 7.2 wt % of Al, which translates to a molar ratio of Al to Zr of ca. 100.

Polymerisation

[0070] In a continuously operated gas-phase fluidised bed reactor having an internal diameter of 45 cm and a reaction zone height of 140 cm, a polymerisation reaction was performed wherein a fluidised bed was maintained by recirculation of a recycle gas stream. The reactor was kept at a constant temperature of 80° C. and at a constant pressure of 21.7 bar. Ethylene and hexene were used in a feed stream comprising the recycled gas, fresh ethylene, 1-hexene and nitrogen, so that the gas stream that was fed to the reactor comprised 53.0 mol % ethylene and [0071] 0.95 mol % 1-hexene in example A, and [0072] 1.55 mol % 1-hexene in example B.

[0073] A quantity of the supported catalyst as produced above was continuously injected into the reactor so that the quantity of zirconium in the reactant mixture was 0.18 wt %. A quantity of 0.08 hg/h of the continuity aid agent was introduced continuously. The produced polymer was discharged from the reactor and purged to remove volatile matter, and treated with humidified nitrogen to deactivate traces of catalyst.

[0074] The thus obtained polymer was subjected to analyses to determine the material properties, which are presented in table 1 below.

TABLE-US-00002 Example A B MFR2 0.7 0.8 MFR5 1.65 1.98 MFR21 12.54 12.41 Density 939 932 Strain hardening 34 49 Charpy at 23° C. 75 103 Charpy at −30° C. 20.8 20.8 C6 4-5 3-6 C6 ratio 1.15 1.65 M.sub.w/M.sub.n 3.47 3.27 M.sub.w 143737 127000 M.sub.n 41358 38800 M.sub.z 289080 297000

Wherein:

[0075] MFR2, MFR5 and MFR21 are the melt mass-flow rate as determined in accordance with ASTM D1238 (2013) at a temperature of 190° C. under a load of 2.16 kg, 5.0 kg and 21.6 kg, respectively, expressed in g/10 min. [0076] Density is determined in accordance with ASTM D792 (2008), expressed in kg/m.sup.3. [0077] Strain hardening is the strain hardening modulus G.sub.p determined in accordance with ISO 18488 (2015), expressed in MPa. [0078] Charpy is the notched Charpy impact strength as determined in accordance with ISO 179-1 (2010), notch type A, edgewise, expressed in kJ/m.sup.2. [0079] C6 is the comonomer branch content in the molecular weight range of log(M.sub.w) between 4.0 and 5.5 expressed as the number of comonomer-derived branches per 1000 carbon atoms in the polymer, as determined via .sup.13C NMR. [0080] C6 ratio is the ratio of the number of comonomer-derived branches per 1000 carbon atoms in the polymer at log(M.sub.w)=5.5 divided by the number of comonomer-derived branches per 1000 carbon atoms in the polymer at log(M.sub.w)=4.0, as determined via 13C NMR:

[00001]$C6\mathrm{ratio}=\frac{\log \left(Mw\right),5.5}{\log \left(Mw\right),4.0}$ [0081] M.sub.w/M.sub.n is the molecular weight distribution as determined in accordance with ASTM D6474 (2012), dimensionless. [0082] M.sub.w is the weight average molecular weight as determined in accordance with ASTM D6474 (2012), in g/mol. [0083] M.sub.n is the number average molecular weight as determined in accordance with ASTM D6474 (2012), in g/mol. [0084] M.sub.z is the z-average molecular weight as determined in accordance with ASTM D6474 (2012), in g/mol.

[0085] From the above, it can be observed that the polymer of example B demonstrated an improved strain hardening and Charpy impact strength at 23° C.