FLUOROPOLYMER PIPE

Abstract

The present invention pertains to a pipe comprising at least one layer at least comprising, preferably consisting essentially of (or being made of), a tetrafluoroethylene (TFE) copolymer comprising from 0.8% to 2.5% by weight of recurring units derived from at least one perfluorinated alkyl vinyl ether having formula (I) here below: CF.sub.2CFOR.sub.f (I) wherein R.sub.f is a linear or branched C.sub.3-C.sub.5 perfluorinated alkyl group or a linear or branched C.sub.3-C.sub.12 perfluorinated oxyalkyl group comprising one or more ether oxygen atoms, said TFE copolymer having a melt flow index comprised between 0.5 and 6.0 g/10 min, as measured according to ASTM D1238 at 372 C. under a load of 5 Kg [polymer (F)]. The invention also pertains to use of said pipe in heat exchangers and in downhole operations including drilling operations.

Claims

1. A pipe being an unbonded flexible riser and comprising at least one layer made of a tetrafluoroethylene (TFE) copolymer consisting of: from 1.2% to 2.5% by weight of recurring units derived from at least one perfluorinated alkyl vinyl ether having formula (I) here below:
CF.sub.2CFOR.sub.f (I) wherein R.sub.f is a linear or branched C.sub.3-C.sub.5 perfluorinated alkyl group or a linear or branched C.sub.3-C.sub.12 perfluorinated oxyalkyl group comprising: one or more ether oxygen atoms, and from 97.5% to 98.8% by weight of recurring units derived from TFE, said TFE copolymer having a melt flow index comprised between 0.5 and 6.0 g/10 min, as measured according to ASTM D1238 at 372 C. under a load of 5 kg, and a melting point comprised between 311 C. and 321 C., polymer (F).

2. The pipe according to claim 1, wherein the polymer (F) has a melt flow index comprised between 0.6 and 5.5 g/10 min, as measured according to ASTM D1238 at 372 C. under a load of 5 kg.

3. The pipe according to claim 1, wherein the perfluorinated alkyl vinyl ether complies with formula (II) here below:
CF.sub.2CFOR.sub.f (II) wherein R.sub.f is a linear or branched C.sub.3-C.sub.5 perfluorinated alkyl group.

4. The pipe according to claim 1, wherein the perfluorinated alkyl vinyl ether is perfluoropropyl vinyl ether (PPVE).

5. The pipe according to claim 1, the pipe being a rough-bore flexible riser.

6. The pipe according to claim 1, the pipe being a smooth-bore flexible riser.

7. The pipe according to claim 1, wherein the tetrafluoroethylene (TFE) copolymer consists of: from 1.4% to 2.2% by weight of recurring units derived from the at least one perfluorinated alkyl vinyl ether having formula (I); and from 97.8% to 98.6% by weight of recurring units derived from TFE.

8. The pipe according to claim 1, wherein the TFE copolymer has a melting point between 311 C. and 318 C.

9. The pipe according to claim 1, wherein the polymer (F) has a melt flow index between 1.2 and 3.5 g/10 min, as measured according to ASTM D1238 at 372 C. under a load of 5 kg.

10. The pipe according to claim 1, wherein the pipe is configured to contact one or more heat exchanger.

11. The pipe according to claim 1, wherein the pipe is configured to extend into a well in downhole operations.

12. The pipe according to claim 1, wherein the pipe is configured to extend into a well in drilling operations.

13. The pipe according to claim 5, the pipe comprising, from an interior towards an exterior: an internal flexible metal tube, called internal carcass, formed by a helically wound profiled member with turns clipped together, an internal polymeric sheath at least comprising the polymer (F), one or more armor plies wound around the internal polymeric sheath, and an external polymeric sheath.

14. The pipe according to claim 13, wherein the internal polymeric sheath consists of the polymer (F).

15. The pipe according to claim 13, wherein the internal polymeric sheath is extruded over the internal carcass of the rough-bore flexible riser by conventional melt-processing techniques.

16. A pipeline system comprising at least two coaxial pipes: an outer metal pipeline, and an inner pipe comprising at least one layer at least comprising a tetrafluoroethylene (TFE) copolymer polymer (F) comprising from 1.2% to 2.5% by weight of recurring units derived from at least one perfluorinated alkyl vinyl ether having formula (I) here below:
CF.sub.2CFOR.sub.f (I), wherein R.sub.f is a linear or branched C.sub.3-C.sub.5 perfluorinated alkyl group, said TFE copolymer having a melt flow index comprised between 0.5 and 6.0 g/10 min, as measured according to ASTM D1238 at 372 C. under a load of 5 kg.

17. The pipeline system according to claim 16, wherein the pipeline system is configured to form one or more heat exchangers.

18. The pipeline system according to claim 16, wherein the pipeline system is configured to extend into a well in downhole operations.

19. The pipeline system according to claim 16, the pipeline system is configured to extend into a well in drilling operations.

20. The pipeline system according to claim 16, wherein the outer metal pipeline is configured to connect to the inner pipe, and wherein a diameter of the inner pipe is less than a diameter of the outer metal pipeline.

Description

EXAMPLE 1

TFE/PPVE 98.2/1.8 (Weight Ratio)

[0169] In an AISI 316 steel vertical 22 litres autoclave, equipped with a stirrer working at 400 rpm, after the vacuum was made, were introduced in sequence: [0170] 13.9 litres of demineralised water; [0171] 32.0 g of perfluoropropylvinyleiher (PPVE); [0172] 138.0 g of a microemulsion prepared according to Example 1 of US 4,864,006 (AUSIMONT S.P.A.) 5 Sept. 1989 having a pH of about 7.5.

[0173] The autoclave was then heated up to reaction temperature of 60 C. and, when this temperature was reached, 0.60 bar of ethane were introduced.

[0174] By a compressor a gaseous mixture of TFE/PPVE in nomi-nal molar ratio of 99.210.8 was added until reaching a pressure of 21 bar.

[0175] The composition of the gaseous mixture present at the autoclave head (as determined by GC analysis) was formed of the following compounds in the indicated molar percentages: 95.9% TFE, 2.0% PPVE, 2.1% ethane.

[0176] Then, by a metering pump, 100 ml of a 0.035 M ammonium persulphate solution were fed.

[0177] The polymerization pressure was maintained constant by feeding the above mentioned monomeric mixture; when 8.8 g of the mixture were fed, the monomer feeding was interrupted. The reactor was cooled to room temperature, the latex was dischar-ged and coagulated with HNO.sub.3 (65% by weight) and the polymer was washed with H.sub.2O and dried at about 220 C.

[0178] Determination of the obtained polymer:

[0179] Composition (IR analysis): PPVE: 1.8% by weight

[0180] MFI: 5.0 g/10 min

[0181] Second melting temperature (T(Il) melting point): 314 C.

EXAMPLE 2

TFE/PPVE 98.6/1.4 (Weight Ratio)

[0182] The same procedure as detailed under Example 1 was followed but: [0183] 25.0 g of PPVE were fed; [0184] 0.50 bar of ethane were fed; [0185] a gaseous mixture of TFE/PPVE in nominal molar ratio of 99.4/0.6 was added.

[0186] The composition of the gaseous mixture present at the autoclave head (as determined by GC analysis) was formed of the following compounds in the indicated molar percentages: 96.90% TEE, 1.55% PPVE, 1.55% ethane.

[0187] Determinations on the obtained polymer:

[0188] Composition (IR analysis): PPVE: 1.4% by weight

[0189] MFI: 3.0 g/10 min

[0190] Second melting temperature (T(II) melting point): 317 C.

EXAMPLE 3

TFE/PPVE 98.6/1.4 (Weight Ratio)

[0191] The same procedure as detained under Example 1 was o owed but: [0192] 25.0 g of PPVE were fed; [0193] 0.40 bar of ethane were fed; [0194] a gaseous mixture of TFE/PPVE in nominal molar ratio of 99.4/0.6 was added; [0195] 150 ml of a 0.035 M ammonium persulphate solution were fed.

[0196] The composition of the gaseous mixture present at the autoclave head (as determined by GC analysis) was formed of the following compounds in the indicated molar percentages: 96.2% TFE, 1.7% PPVE, 2.1% ethane.

[0197] Determinations on the obtained polymer:

[0198] Composition (IR analysis): PPVE: 1.5% by weight

[0199] MFI: 2.0 g/10 min

[0200] Second melting temperature (T(II) melting point): 316 C.

[0201] As shown in Table 1 here below, reporting the results of yield strength tests at 280 C., the polymers (F) according to the invention advantageously exhibited improved yield stress values at temperatures up to 280 C. as compared with commercially available products of comparative Examples 1 and 2.

TABLE-US-00001 TABLE 1 PPVE MFI Tm Yield stress Run [% wt.] [g/10 min] [ C.] [MPa] Example 1 1.8 5.0 314 3.6 Example 2 1.4 3.0 317 3.5 Example 3 1.5 2.0 316 3.5 C. Example 1 3.8 2.5 307 2.8 C. Example 2 3.3 2.5 310 3.2

[0202] As shown in Table 2 here below, reporting the results of the creep strain tests, the polymers (F) according to the invention advantageously exhibited lower creep strain values as compared with commercially available product of comparative Example 2.

TABLE-US-00002 TABLE 2 Creep strain Creep strain MFI 280 C. 300 C. PPVE [g/10 Tm 1.0 MPa 1.0 MPa Run [% wt.] min] [ C.] (1000 hours) (1000 hours) Example 2 1.4 3.0 317 12.0% Example 3 1.5 2.0 317 9.3% 20.0% C. Example 2 3.3 2.5 310 17.8% >40%

[0203] As shown in Table 3 here below, pipes were obtained using the polymer (F) according to the present invention which advantageously were endowed with shrinkage values at 300 C. comparable to those of commercially available product of comparative Example 1.

TABLE-US-00003 TABLE 3 PPVE MFI Tm Shrinkage Run [% wt.] [g/10 min] [ C.] 300 C. Example 3 1.5 5.0 317 2.3% C. Example 1 3.8 2.5 307 3.0%

[0204] It has been thus found that the pipe of the present invention comprising at least one layer at least comprising, preferably consisting essentially of (or being made of), the polymer (F) advantageously exhibits enhanced yield strength values, both in short-term and long-term trials, in particular at high operating temperatures, so that it can successfully withstand high internal pressure levels because of its improved mechanical properties.

EXAMPLE 4

TFE/PPVE 97.8/2.2 (Weight Ratio)

[0205] The same procedure as detained under Example 1 was followed but: [0206] 38 g of PPVE were fed; [0207] 0.51 bar of ethane were fed; and [0208] a gaseous mixture of TFE/PPVE in nominal molar ratio of 98.8/1.2 was added.

[0209] The composition of the gaseous mixture present at the autoclave head (as determined by GC analysis) was formed of the following compounds in the indicated molar percentages: 93.0% TFE, 6.2% PPVE, 0.7% ethane.

[0210] Determinations on the obtained polymer:

[0211] Composition (IR analysis): PPVE: 2.2% by weight

[0212] MFI: 3.3 g/10 min

[0213] Second melting temperature (T(II) melting point): 311.4 C.

EXAMPLE 5

TFE/PPVE 97.8/2.2 (Weight Ratio)

[0214] The same procedure as detained under Example 1 was followed but: [0215] 38 g of PPVE were fed; [0216] 0.35 bar of ethane were fed; and [0217] a gaseous mixture of TFE/PPVE in nominal olar ratio of 98.8/1.2 was added.

[0218] The composition of the gaseous mixture present at the autoclave head (as determined by GC analysis) was formed of the following compounds in the indicated molar percentages: 93.5% TFE, 6.0% PPVE, 0.5% ethane.

[0219] Determinations on the obtained polymer:

[0220] Composition (IR analysis): PPVE: 2.2% by weight

[0221] MFI: 1.7 g/10 min

[0222] Second melting temperature (T(II) melting point): 311.6 C.

[0223] As shown in Table 4 here below, reporting the results of tensile tests at 23 C., pipes made of the polymers (F) according to the invention as notably represented by Example 4 or 5 of the invention advantageously exhibited a combination of mechanical properties such that said pipes can be suitably used in a process for lining a metal pipeline.

TABLE-US-00004 TABLE 4 Yield Stress at Strain at Modulus Stress Break Break Run [MPa] [MPa] [MPa] [MPa] Example 4 424 13.3 29.6 311 Example 5 443 13.4 30.2 320

[0224] As shown in Table 5 here below, reporting the results of the creep strain tests, pipes made of the polymer (F) according to the invention as notably represented by Example 4 of the invention advantageously exhibited relatively low creep strain values without undergoing yielding failure under relatively high stress of 3.0 MPa and 4.0 MPa to be suitably used in a process for lining a metal pipeline.

TABLE-US-00005 TABLE 5 Creep strain Creep strain MFI 200 C. 200 C. PPVE [g/10 Tm 3.0 MPa 4.0 MPa Run [% wt] min] [ C.] (1000 hours) (1000 hours) Example 4 2.2 3.3 311 14.4% 33.8%

[0225] As shown in Table 6 here below, reporting the results of the rapid gas decompression (RGD) tests, pipes made of the polymer (F) according to the invention as notably represented by Example 5 advantageously exhibited no visible cracks to be suitably used in a process for lining a metal pipeline in downhole applications without undergoing decompression under the effect of pressure impacts.

TABLE-US-00006 TABLE 6 Run Visible RGD damages Example 5 After 20 RGD cycles: no visible cracks

[0226] The pipe of the present invention is thus particularly suitable for use in operations where high thermal resistance at high operating temperatures is required.