Fluoroelastomers

Abstract

The invention pertains to peroxide-curable fluoroelastomers for the oil and gas industry, including explosive decompression, and which can be easily processed to yield cured parts in standard machineries at reasonable throughput rates, said fluoroelastomers comprising: recurring units derived from vinylidene fluoride (VDF); recurring units derived from hexafluoropropylene (HFP); recurring units derived from at least one bis-olefin [bis-olefin (OF)] having general formula: ##STR00001##
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6, equal or different from each other, are H, a halogen, or a C.sub.1-C.sub.5 optionally halogenated group, possibly comprising one or more oxygen group; Z is a linear or branched C.sub.1-C.sub.18 optionally halogenated alkylene or cycloalkylene radical, optionally containing oxygen atoms, or a (per)fluoropolyoxyalkylene radical; and iodine or bromine cure-sites;
said fluoroelastomers further possessing a Mooney viscosity (ML) of at least 85 MU (1+10@121 C.), when measured according to ASTM D1646.

Claims

1. A method for extracting or transporting fluids in the energy or in the oil and gas industry, comprising passing the fluid through an oil and gas device comprising at least one cured article obtained from a fluoroelastomer (A), wherein the fluoroelastomer (A) comprises: at least 35% moles and at most 85% moles of recurring units derived from vinylidene fluoride (VDF), with respect to all recurring units of the fluoroelastomer; at least 10% moles and at most 45% moles of recurring units derived from hexafluoropropylene (HFP), with respect to all recurring units of the fluoroelastomer; recurring units derived from at least one bis-olefin (OF) having general formula: ##STR00007## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6, equal or different from each other, are H, a halogen, or a C.sub.1-C.sub.5 optionally halogenated group, optionally comprising one or more oxygen group; Z is a linear or branched C.sub.1-C.sub.18 optionally halogenated alkylene or cycloalkylene radical, optionally containing oxygen atoms, or a (per)fluoropolyoxyalkylene radical; at least 0.5% moles and at most 35% moles, of recurring units derived from tetrafluoroethylene (TFE), with respect to all recurring units of the fluoroelastomer; and iodine or bromine cure-sites; said fluoroelastomer possessing a Mooney viscosity (ML) of at least 85 MU (1+10@121 C.), when measured according to ASTM D1646, and said fluoroelastomer has a tensile strength at 23 C., according to the DIN 53504 S2 Standard, ranging from 25 to 31.3 MPa.

2. The method of claim 1, wherein the fluoroelastomer has a Mooney viscosity (ML) of at most 130 MU (1+10@121 C.), when measured according to ASTM D1646.

3. The method of claim 1, wherein the fluoroelastomer has a Mooney viscosity (ML) of at least 86 MU (1+10@121 C.), when measured according to ASTM D1646.

4. The method of claim 3, wherein the fluoroelastomer has a Mooney viscosity (ML) of at most 125 MU (1+10@121 C.), when measured according to ASTM D1646.

5. The method of claim 1, wherein the fluoroelastomer has a Mooney viscosity (ML) of at least 87 MU (1+10@121 C.), when measured according to ASTM D1646.

6. The method of claim 5, wherein the fluoroelastomer has a Mooney viscosity (ML) of at most 120 MU (1+10@121 C.), when measured according to ASTM D1646.

7. The method of claim 1, wherein the recurring units derived from vinylidene fluoride (VDF) are present in an amount ranging from at least 45% moles and at most 80% moles, with respect to all recurring units of the fluoroelastomer; wherein the recurring units derived from hexafluoropropylene (HFP) are present in an amount ranging from at least 15% moles and at most 25% moles, with respect to all recurring units of the fluoroelastomer; and wherein the recurring units derived from tetrafluoroethylene (TFE) are present in an amount ranging from at least 10% moles and at most 30% moles, with respect to all recurring units of the fluoroelastomer.

8. The method of claim 1, comprising, in addition to recurring units derived from said bis-olefin (OF), said VDF and said HFP: recurring units derived from at least one (per)fluorinated monomer different from said VDF and said HFP; and optionally, recurring units derived from at least one hydrogenated monomer.

9. The method of claim 8, wherein said (per)fluorinated monomer is selected from the group consisting of: (a) C.sub.2-C.sub.8 perfluoroolefins; (b) hydrogen-containing C.sub.2-C.sub.8 olefins; (c) C.sub.2-C.sub.8 chloro and/or bromo and/or iodo-fluoroolefins; (d) (per)fluoroalkylvinylethers (PAVE) of formula CF.sub.2CFOR.sub.f, wherein R.sub.f is a C.sub.1-C.sub.6 (per)fluoroalkyl group; (e) (per)fluoro-oxy-alkylvinylethers of formula CF.sub.2CFOX, wherein X is a C.sub.1-C.sub.12 ((per)fluoro)-oxyalkyl comprising catenary oxygen atoms; (f) (per)fluorodioxoles having formula: ##STR00008## wherein R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6, equal or different from each other, are independently selected from the group consisting of fluorine atoms and C.sub.1-C.sub.6 (per)fluoroalkyl groups, optionally comprising one or more than one oxygen atom; and (g) (per)fluoro-methoxy-vinylethers (MOVE) having formula: CFX.sub.2CX.sub.2OCF.sub.2OR.sub.f wherein R.sub.f is selected from the group consisting of C.sub.1-C.sub.6 (per)fluoroalkyls, linear or branched; C.sub.5-C.sub.6 cyclic (per)fluoroalkyls; and C.sub.2-C.sub.6 (per)fluorooxyalkyls, linear or branched, comprising from 1 to 3 catenary oxygen atoms, and X.sub.2F, H.

10. The method of claim 9, further comprising: recurring units derived from at least one hydrogenated monomer and/or recurring units derived from at least one other (per)fluorinated monomer different from said VDF, said HFP and said TFE.

11. The method of claim 1, wherein said bis-olefin (OF) is selected from the group consisting of those complying with formulae (OF-1), (OF-2) and (OF-3): ##STR00009## wherein j is an integer between 2 and 10, and R.sub.1, R.sub.2, R.sub.3, R.sub.4, equal or different from each other, are H, F or C.sub.1-5 alkyl or (per)fluoroalkyl group; ##STR00010## wherein each of A, equal or different from each other and at each occurrence, is independently selected from F, Cl, and H; each of B, equal or different from each other and at each occurrence, is independently selected from F, Cl, H and OR.sub.B, wherein R.sub.B is a branched or straight chain alkyl radical which can be partially, substantially or completely fluorinated or chlorinated; E is a divalent group having 2 to 10 carbon atom, optionally fluorinated, which may be inserted with ether linkages; ##STR00011## wherein E, A and B have the same meaning as above defined; R.sub.5, R.sub.6, R.sub.7, equal or different from each other, are H, F or C.sub.1-5 alkyl or (per)fluoroalkyl group.

12. The method of claim 1, wherein the amount of recurring units derived from said bis-olefin (OL) is of at least 0.01% moles, and of at most 5.0% moles, with respect to all other recurring units of the fluoroelastomer.

13. Drilling and raiser devices for extraction and transportation of crude oil comprising at least one cured article comprising a fluoroelastomer (A) that comprises: at least 35% moles and at most 85% moles of recurring units derived from vinylidene fluoride (VDF), with respect to all recurring units of the fluoroelastomer; at least 10% moles and at most 45% moles of recurring units derived from hexafluoropropylene (HFP), with respect to all recurring units of the fluoroelastomer; recurring units derived from at least one bis-olefin (OF) having general formula: ##STR00012## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6, equal or different from each other, are H, a halogen, or a C.sub.1-C.sub.5 optionally halogenated group, optionally comprising one or more oxygen group; Z is a linear or branched C.sub.1-C.sub.18 optionally halogenated alkylene or cycloalkylene radical, optionally containing oxygen atoms, or a (per)fluoropolyoxyalkylene radical; at least 0.5% moles and at most 35% moles, of recurring units derived from tetrafluoroethylene (TFE), with respect to all recurring units of the fluoroelastomer; and iodine or bromine cure-sites; said fluoroelastomer possessing a Mooney viscosity (ML) of at least 85 MU (1+10@121 C.), when measured according to ASTM D1646, and said fluoroelastomer has a tensile strength at 23 C., according to the DIN 53504 S2 Standard, ranging from 25 to 31.3 MPa.

14. The method of claim 12, wherein the amount of recurring units derived from said bis-olefin (OL) is of at least 0.05% moles, and of at most 0.2% moles, with respect to all other recurring units of the fluoroelastomer.

15. The method of claim 11, wherein the fluoroelastomer (A) comprises, all with respect to all other recurring units of the fluoroelastomer: at least 45% moles and at most 78% moles of recurring units derived from VDF; at least 15% moles and at most 35% moles of recurring units derived from HFP; at least 0.05% moles, and of at most 0.2% moles recurring units derived from OF-1; and at least % moles and at most 28% moles, of recurring units derived from TFE, wherein the fluoroelastomer possesses a Mooney viscosity (ML) of at least 85 MU and at most 120 MU (1+10@121 C.), when measured according to ASTM D1646.

Description

EXAMPLES

Comparative Example 1

HNBR Rubber

(1) A HNBR rubber commercially available from Zeon under trade name ZEPTOL 2000 was used for comparative purposes, being understood that HNBR rubber are generally considered as state of the art materials for rapid gas decompression behaviour.

Example 2

Manufacture of a VDF/TFE/HFP Terpolymer having a Mooney Viscosity of 88 MU (1+10@121 C.).

(2) Fluoroelastomer of example 2 was produced according to following procedure:

(3) In a 22 l autoclave, equipped with stirrer working at 460 rpm, were introduced, after evacuation 13.0 l of demineralized water and 97.5 ml of a perfluoropolyoxyalkylene microemulsion previously obtained by mixing: 21.20 ml of an acid terminated perfluoropolyoxyalkylene of formula:
CF.sub.3O(CF.sub.2CF(CF.sub.3)O).sub.n(CF.sub.2O).sub.mCF.sub.2COOH,

(4) wherein n/m=10, and having an average molecular weight of 600;

(5) 7.45 ml of 30% by volume NH.sub.4OH aqueous solution;

(6) 56.16 ml demineralized water;

(7) 12.69 ml of GALDEN D02 PFPE of formula:
CF.sub.3O(CF.sub.2CF(CF.sub.3)O).sub.n(CF.sub.2O).sub.mCF.sub.3

(8) wherein n/m=20, and having an average molecular weight of 450.

(9) The autoclave was then heated to 80 C. and maintained at such temperature for the entire duration of the reaction. A gazeous mixture of following monomers: vinylidene fluoride (VDF) 47.5% by moles; hexafluoropropene (HFP) 45% by moles; tetrafluoroethylene (TFE) 7.5% by moles, was introduced in the autoclave so as to bring the pressure to 26 bar. 1.04 g of ammonium persulphate (APS) were then introduced in 2 step-wise additions, 0.71 g at the beginning of polymerization and 0.33 g at 20% increment in the monomer conversion. Also, 38.57 g of 1,4-diiodoperfluorobutane (C.sub.4F.sub.8I.sub.2) were step-wise introduced as chain transfer agent, a first portion of 5.79 g at the beginning of polymerization, 17.36 g at 20% increment in the monomer conversion and 15.42 g at 80% increment in the monomer conversion. Further, 27.08 g of a bis-olefin having the formula CH.sub.2CH(CF.sub.2).sub.6CHCH.sub.2 were added in 20 equal parts, each of 1.354 g, beginning from the polymerization starting and for every 5% increment in the monomer conversion. Set-point pressure of 26 bar was maintained constant during polymerization by feeding a mixture consisting of: VDF 70% by moles; HFP 19% by moles; TFE 11% by moles. After 207 min the autoclave was cooled, and the latex was discharged. 451.8 g/l of latex of a terpolymer having Mooney viscosity, ML (1+10) at 121 C. (ASTM D 1646), equal to 88, were thus obtained. The iodine content and the molar monomer composition in the terpolymer were found to be, respectively, 0.24% by weight and VDF 70.6, HFP 17.7, TFE 11.7% by moles; NMR analysis confirmed incorporation in the fluoroelastomer chain of recurring units derived from the above mentioned bis-olefin in an amount of about 0.1% moles, with respect to all other recurring units mentioned above.

Example 3

Manufacture of a VDF/TFE/HFP Terpolymer Having a Mooney Viscosity of 110 MU (1+10@121 C.)

(10) Substantially same procedure followed in example 2 was used, in an autoclave of inner volume of 10 litres agitated at 545 rpm, but: initially charging the autoclave with a gazeous mixture of following monomers: VDF: 17% by moles; HFP: 70% by moles; TFE: 13% by moles 'til set-point pressure of 26 bar; initiating reaction by addition of 0.51 g APS (0.35 at the beginning and 0.16 g at 20% increment in conversion, of 18.06 g of C.sub.4F.sub.8I.sub.2 (2.71 g at the beginning, 8.13 g at 20% conversion and 7.22 g at 20% conversion) and of 12.13 g of same bis-olefin (in 20 equal parts of 0.61 g every 5% increment of conversion); and maintaining set-point pressure of 26 bar by addition of a mixture consisting of: VDF 48% by moles; HFP 27% by moles; TFE 25% by moles.

(11) After 125 min the autoclave was cooled, and the latex was discharged. 416.1 g/l of latex of a terpolymer having Mooney viscosity, ML (1+10) at 121 C. (ASTM D 1646), equal to 110, were thus obtained. The iodine content and the molar monomer composition in the terpolymer were found to be, respectively, 0.23% by weight and VDF 49.5, HFP 24.6, TFE 25.9% by moles; NMR analysis confirmed incorporation in the fluoroelastomer chain of recurring units derived from the above mentioned bis-olefin in an amount of about 0.1% moles, with respect to all other recurring units mentioned above.

Comparative Example 4

Manufacture of a VDF/TFE/HFP Terpolymer having a Mooney Viscosity of 76 MU (1+10@121 C.) According to EP0967248

(12) A terpolymer was manufacture according to the teachings of example 3B of EP 0967248 A (AUSIMONT SPA) 23 Jun. 1998 for comparative purposes.

(13) Adopting procedure described therein, after 112 min of reaction, a latex was obtained comprising 421 g/l of a terpolymer having Mooney viscosity, ML (1+10) at 121 C. (ASTM D 1646), equal to 76. The iodine content and the molar monomer composition in the terpolymer were found to be, respectively, 0.20% by weight and VDF 52.2, HFP 24.0, TFE 23.8% by moles, and bis-olefin (about 0.1% moles with respect to all other recurring units).

(14) Mechanical and Chemical Resistance Property Determination on Cured Samples

(15) Fluoroelastomers were compounded with the additives as detailed in following table in a Brabender mixer. Plaques and O-rings (size class=214) have been cured in a pressed mould and then post-treated in an air circulating oven in conditions (time, temperature) below specified.

(16) The tensile properties have been determined on specimens punched out from the plaques, according to the DIN 53504 S2 Standard.

(17) M 50 is the tensile strength in MPa at an elongation of 50%

(18) M 100 is the tensile strength in MPa at an elongation of 100%

(19) T.S. is the tensile strength in MPa;

(20) E.B. is the elongation at break in %.

(21) The Shore A hardness (3) (HDS) has been determined on 3 pieces of plaque piled according to the ASTM D 2240 method.

(22) The compression set (C-SET) has been determined on O-ring, spaceman standard AS568A (type 214) or on 6 mm buttons (type 2), according to the ASTM D 395, method B.

(23) Mooney viscosity (ML) (1+10@121 C.) was determined according to ASTM D1646.

(24) Chemical resistance was evaluated according ASTM D471 standard; more precisely, a IRM903 test at 125 and 150 C. during 70 h and a diethanolamine (1% water solution) test at 100 C. during 168 h. Results are summarized herein below in tables 2 to 4.

(25) TABLE-US-00001 TABLE 1 Run 1C 2 3 4C Elastomer Zeptol 2000 phr 100 Fluoroelastomer of ex. 2 phr 100 Fluoroelastomer of ex. 3 phr 100 Fluoroelastomer of phr 100 comparative ex. 4 Other ingredients TAIC.sup.(*.sup.) phr 4 4 4 Peroxide.sup.(**.sup.) phr 1 1 1 Carbon black.sup.(***.sup.) phr 50 40 40 Press cure 20 at 8 at 5 at 4 at 170 C. 170 C. 170 C. 170 C. Post cure 4 h at 4 h at 4 h at 4 h at 150 C. 230 C. 230 C. 230 C. Mechanical Properties at room temperature (23 C.) Tensile Strength MPa 29.6 25 31.3 16.8 100% Modulus MPa 16.5 17.7 24.7 n.d..sup.(+) Elongation @ Break % 169 127 117 89 Hardness (Shore A) pts 88 90 90 87 Mechanical Properties at 120 C. Tensile Strength MPa 11.2 11.2 12.6 6 100% Modulus MPa n.d..sup.(+) 11.2 n.d..sup.(+) n.d..sup.(+) Elongation @ Break % 90 101 87 50 Mechanical Properties at 150 C. Tensile Strength MPa 9 9.2 10.5 5.6 Elongation @ Break % 79 90 77 46 Sealing properties C-set 70 h at 200 C. % 47 23 15 16 (6 mm button) Tear strength Test Temperature 23 C. Tear Strength N/mm 42.4 33 32.9 30.4 Test Temperature 120 C. Tear Strength N/mm 18.4 17.7 14.4 14.1 Test Temperature 150 C. Tear Strength N/mm 15.9 12 12.9 11.7 .sup.(*.sup.)Crosslinking agent: Drimix TAIC 75 supported (triallyl isocyanurate 75% supported on synthetic calcium silicate) .sup.(**.sup.)Catalyst agent: LUPEROX 101 (ex. 1C and 2) or TRIGONOX 101 (ex. 3 and 4), both neat 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (C.sub.16H.sub.34O.sub.4); .sup.(***.sup.)Reinforced filler Carbon black N550 FEF; .sup.(+)not measurable; when elongation at break is lower than 100%, determination of modulus at 100% elongation is impossible.

(26) Chemical Resistance Evaluation

(27) Test IRM 903 125 C. for 70 hoursDifferences (in % and in points HDS) found in mechanical properties, hardness, weight and volume in specimens submitted to the test.

(28) TABLE-US-00002 TABLE 2 M50 M100 T.S. EB HDS Wt Vol [%] [%] [%] [%] [pt] [%] [%] Ex. 1C 23 8 20% 16 8 12 16 Ex. 2 14 11 9% 1 1 0.8 1.6

(29) Test IRM 903 150 C. for 70 hoursDifferences found in mechanical properties, hardness, weight and volume in specimens submitted to the test.

(30) TABLE-US-00003 TABLE 3 M50 M100 T.S. EB HDS Wt Vol [%] [%] [%] [%] [pt] [%] [%] Ex. 1C 17 3 20 18 8 13 17 Ex. 2 22 20% 15 3 2 1.5 2.9

(31) Test in diethanolamine (1% water) at 100 C. during 168 hDifferences found in mechanical properties, hardness, weight and volume in specimens submitted to the test.

(32) TABLE-US-00004 TABLE 3 M50 M100 T.S. EB HDS Wt Vol [%] [%] [%] [%] [pt] [%] [%] Ex. 1C 10 8 2 6 1 2.0 2.5 Ex. 2 9 10 4 9 1 0.9 1.7

(33) Formulations as detailed in table 1 were designed to provide similar hardness of about 90 ShA, by appropriate tuning of the amount of filler.

(34) From the data of table 1, it is evident that the fluoroelastomers of the invention (examples 2 and 3) develop mechanical properties at room and at high temperature as good as HNBR (comparative example 1) and much better than the fluoroelastomers of the prior art (comparative example 4). Indeed, with the same initial hardness, the fluoroelastomers of the invention maintain a tensile strength of about 10 M Pa even at 150 C. while keeping an elongation at break close to 100%. This is not true for Comparative Example 4 where tensile at break and elongation at break at high temperature vanishes. Further, compression set data of table 1 show that sealing performance of fluoroelastomers are much better than those of HNBR based compound. Tear strength resistance of inventive compounds is also better than that of fluoroelastomer of the prior art.

(35) Data in tables 2, 3 and 4 shows that the fluoroelastomers of the present invention have much better chemical resistance than HNBR based compounds. This is particularly true in very aggressive environments like those of tables 2 and 3.

(36) It is thus clear that the fluoroelastomers of the invention are the only polymers having at the same time good mechanical properties at high temperature and good chemical resistance in very aggressive environments. This combination of property is particularly important in oil field industry where, being in contact with drilling mud, the sealing elements are subjected to aggressive fluids at high temperature.

(37) This peculiar combination of very good chemical resistance and very good mechanical properties at high temperature implies that the fluoroelastomers of the present invention are able to sustain very harsh conditions like those occurring during rapid gas decompression conditions.