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.2=CFORf (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 process for lining a metal pipeline, said process comprising the following steps: (i) providing a 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.2=CF-OR.sub.f(I), wherein Rf 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, said pipe having an outer diameter greater than an inner diameter of a metal pipeline; (ii) deforming said pipe thereby providing a deformed pipe having an outer diameter smaller than the inner diameter of said metal pipeline; (iii) introducing the deformed pipe in said metal pipeline; and (iv) expanding the deformed pipe so as to fit with the inner diameter of said metal pipeline.

2. The process according to claim 1, wherein the polymer (F) comprises from 1.2% to 2.5% by weight by weight of recurring units derived from at least one perfluorinated alkyl vinyl ether having formula (I) as defined in claim 1.

3. The process according to claim 1, wherein the polymer (F) consists essentially of: from 1.2% to 2.5% by weight by weight of recurring units derived from at least one perfluorinated alkyl vinyl ether having formula (I) as defined in claim 1, and from 97.5% to 98.8% by weight by weight of recurring units derived from TFE.

4. The process according to claim 3, wherein the polymer (F) consists essentially of: from 1.4% to 2.2% by weight by weight of recurring units derived from at least one perfluorinated alkyl vinyl ether having formula (I) as defined in claim 1, and from 97.8% to 98.6% by weight by weight of recurring units derived from TFE.

5. The process 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.

6. The process according to claim 2, wherein the polymer (F) has a melt flow index comprised between 1.2 and 3.5 g/10 min, as measured according to ASTM D1238 at 372 C. under a load of 5 kg.

7. The process according to claim 1, wherein the polymer (F) has a melting point comprised between 311 C. and 321 C.

8. The process according to claim 4, wherein the polymer (F) has a melting point comprised between 311 C. and 318 C.

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

10. The process according to claim 1, wherein the pipe provided in step (i) is a monolayer pipe.

11. The process according to claim 1, wherein the pipe provided in step (i) is a multilayer pipe.

Description

EXAMPLE 1

TFE/PPVE 98.2/1.8 (Weight Ratio)

[0172] 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:

[0173] 13.9 litres of demineralised water;

[0174] 32.0 g of perfluoropropylvinylether (PPVE);

[0175] 138.0 g of a microemulsion prepared according to Example 1 of U.S. Pat. No. 4,864,006 (AUSIMONT S. P. A.) Sep. 5, 1989 having a pH of about 7.5.

[0176] 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. By a compressor a gaseous mixture of TFE/PPVE in nomi-nal molar ratio of 99.2/0.8 was added until reaching a pressure of 21 bar.

[0177] 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.

[0178] Then, by a metering pump, 100 ml of a 0.035 M ammonium persulphate solu-tion were fed.

[0179] 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.

[0180] Determination of the obtained polymer:

[0181] Composition (IR analysis): PPVE: 1.8% by weight

[0182] MFI: 5.0 g/10 min

[0183] Second melting temperature (T(II) melting point): 314 C.

EXAMPLE 2

TFE/PPVE 98.6/1.4 (Weight Ratio)

[0184] The same procedure as detailed under Example 1 was followed but:

[0185] 25.0 g of PPVE were fed;

[0186] 0.50 bar of ethane were fed;

[0187] a gaseous mixture of TFE/PPVE in nominal molar ratio of 99.4/0.6 was added.

[0188] 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% TFE, 1.55% PPVE, 1.55% ethane.

[0189] Determinations on the obtained polymer:

[0190] Composition (IR analysis): PPVE: 1.4% by weight

[0191] MFI: 3.0 g/10 min

[0192] Second melting temperature (T(II) melting point): 317 C.

EXAMPLE 3

TFE/PPVE 98.6/1.4 (Weight Ratio)

[0193] The same procedure as detained under Example 1 was followed but:

[0194] 25.0 g of PPVE were fed;

[0195] 0.40 bar of ethane were fed;

[0196] a gaseous mixture of TFE/PPVE in nominal molar ratio of 99.4/0.6 was added;

[0197] 150 ml of a 0.035 M ammonium persulphate solution were fed.

[0198] 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.

[0199] Determinations on the obtained polymer:

[0200] Composition (IR analysis): PPVE: 1.5% by weight

[0201] MFI: 2.0 g/10 min

[0202] Second melting temperature (T(II) melting point): 316 C.

[0203] 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

[0204] 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 280 C. 300 C. PPVE MFI Tm 1.0 MPa 1.0 MPa Run [% wt.] [g/10 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%

[0205] 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%

[0206] 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)

[0207] The same procedure as detained under Example 1 was followed but:

[0208] 38 g of PPVE were fed;

[0209] 0.51 bar of ethane were fed; and

[0210] a gaseous mixture of TFE/PPVE in nominal molar ratio of 98.8/1.2 was added.

[0211] 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.

[0212] Determinations on the obtained polymer:

[0213] Composition (IR analysis): PPVE: 2.2% by weight

[0214] MFI: 3.3 g/10 min

[0215] Second melting temperature (T(II) melting point): 311.4 C.

EXAMPLE 5

TFE/PPVE 97.8/2.2 (Weight Ratio)

[0216] The same procedure as detained under Example 1 was followed but:

[0217] 38 g of PPVE were fed;

[0218] 0.35 bar of ethane were fed; and

[0219] a gaseous mixture of TFE/PPVE in nominal molar ratio of 98.8/1.2 was added.

[0220] 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.

[0221] Determinations on the obtained polymer:

[0222] Composition (IR analysis): PPVE: 2.2% by weight

[0223] MFI: 1.7 g/10 min

[0224] Second melting temperature (T(II) melting point): 311.6 C.

[0225] 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 Modulus Yield Stress Stress at Break Strain at Break Run [MPa] [MPa] [MPa] [MPa] Example 4 424 13.3 29.6 311 Example 5 443 13.4 30.2 320

[0226] 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 200 C. 200 C. PPVE MFI Tm 3.0 MPa 4.0 MPa Run [% wt.] [g/10 min] [ C.] (1000 hours) (1000 hours) Example 4 2.2 3.3 311 14.4% 33.8%

[0227] 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

[0228] The pipe of the present invention is thus particularly suitable for use in operations where high thermal resistance at high operating temperatures is required.