FLUOROELASTOMER COMPOSITION

Abstract

The invention pertains to a fluoroelastomer composition comprising:—at least one fluoroelastomer [perfluoroelastomer (A)], said fluoroelastomer (A) comprising iodine and/or bromine atoms and having a backbone comprising:—recurring units derived from tetrafluoroethylene (TFE);—recurring units derived from at least one perfluorinated monomer selected from the group consisting of:—perfluoroalkylvinylethers complying with formula CF.sub.2═CFOR.sub.f1 in which Rn is a C.sub.1-C.sub.6 perfluoroalkyl (monomers of this type being referred to, herein after, as PAVE), e.g. —CF.sub.3, —C.sub.2F.sub.5, —C.sub.3F.sub.7;—perfluoro-oxyalkylvinylethers complying with formula CF.sub.2=CFOX.sub.0, in which X.sub.0 can be (i) a C.sub.1-C.sub.12 perfluorooxyalkyl having one or more ether groups, e.g. —C.sub.2F.sub.5—O—CF.sub.3; or (ii) a group of formula —CF.sub.2OR.sub.f2 in which R.sub.f2 is a C.sub.1-C.sub.6 perfluoroalkyl, e.g. —CF.sub.3, —C.sub.2F.sub.5, —C.sub.3F.sub.7 (monomers of this type being referred to, herein after, as MOVE);—recurring units derived from vinylidene fluoride (VDF) in an amount of up to 30% by moles, with respect to the total moles of recurring units; and—optionally, recurring units derived from at least one perfluorinated C.sub.3-C.sub.8 alpha-olefin, in an amount of up to 5% moles;—optionally, recurring units derived from at least one fluorine-free alpha-olefin, in an amount of up to 10% moles;—from 0.5 to 5 weight parts, per 100 parts by weight of said fluoroelastomer (A), of at least one polyunsaturated compound;—from 0.1 to 3 weight parts, per 100 parts by weight of said fluoroelastomer (A), of at least one organic peroxide;—from 0.1 to 3 weight parts, per 100 parts by weight of said fluoroelastomer (A), of at least one organic base [base (B)] selected from the group consisting of: (i) non-aromatic primary amines or amides complying with general formula (B1m) or (B1d): R.sub.bm—[C(0)].sub.t-NH.sub.2 (B1m) H.sub.2N—[C(O)].sub.t′—R.sub.dm—[C(O)].sub.t″—NH.sub.2 (B1d) wherein:—each of t, t′ and t″, equal to or different from each other and at each occurrence is zero or 1;—R.sub.bm is a monovalent hydrocarbon non-aromatic group having 12 to 30 carbon atoms;—R.sub.bm is a divalent hydrocarbon non-aromatic group having 6 to 30 carbon atoms; and (ii) cycloaliphatic secondary or tertiary amines complying with general formula (B2m) or (B2d) wherein:—Cy represents a divalent aliphatic group comprising at least 4 carbon atoms, optionally comprising one or more than one ethylenically unsaturated double bond, and optionally comprising one or more catenary nitrogen atoms, forming a cycle with the nitrogen atom which is connected thereto;—Cy′ represent a trivalent aliphatic group comprising at least 5 carbon atoms, optionally comprising one or more than one ethylenically unsaturated double bond, and optionally comprising one or more catenary nitrogen atoms, forming a cycle with the nitrogen atom which is connected thereto.

Claims

1. A fluoroelastomer composition comprising: at least one fluoroelastomer (A), said fluoroelastomer (A) comprising iodine and/or bromine atoms and having a backbone comprising: recurring units derived from tetrafluoroethylene (TFE); recurring units derived from at least one perfluorinated monomer selected from the group consisting of: PAVE monomers, wherein PAVE monomers are perfluoroalkylvinylethers complying with formula CF.sub.2═CFOR.sub.f1 in which R.sub.f1 is a C.sub.1-C.sub.6 perfluoroalkyl; MOVE monomers, wherein MOVE monomers are perfluoro-oxyalkylvinylethers complying with formula CF.sub.2═CFOX.sub.0, in which X.sub.0 is (i) a C.sub.1-C.sub.12 perfluorooxyalkyl having one or more ether groups; or (ii) a group of formula —CF.sub.2OR.sub.f2 in which R.sub.f2 is a C.sub.1-C.sub.6 perfluoroalkyl; recurring units derived from vinylidene fluoride (VDF) in an amount of up to 30% by moles, with respect to the total moles of recurring units; and optionally, recurring units derived from at least one perfluorinated C.sub.3-C.sub.8 alpha-olefin, in an amount of up to 5% moles; optionally, recurring units derived from at least one fluorine-free alpha-olefin, in an amount of up to 10% moles; from 0.5 to 5 weight parts, per 100 parts by weight of said fluoroelastomer (A), of at least one polyunsaturated compound; from 0.1 to 3 weight parts, per 100 parts by weight of said fluoroelastomer (A), of at least one organic peroxide; from 0.1 to 3 weight parts, per 100 parts by weight of said fluoroelastomer (A), of at least one organic base (B) selected from the group consisting of: (i) non-aromatic primary amines or amides complying with general formula (B1m) or (B1d):
R.sub.bm—[C(O)].sub.t—NH.sub.2  (B1m)
H.sub.2N—[C(O)].sub.t′—R.sub.dm—[C(O)].sub.t″—NH.sub.2  (B1d) wherein: each of t, t′ and t″, equal to or different from each other and at each occurrence is zero or 1; R.sub.bm is a monovalent hydrocarbon non-aromatic group having 12 to 30 carbon atoms; R.sub.bm is a divalent hydrocarbon non-aromatic group having 6 to 30 carbon atoms; and (ii) cycloaliphatic secondary or tertiary amines complying with general formula (B2m) or (B2d): ##STR00009## wherein: Cy represents a divalent aliphatic group comprising at least 4 carbon atoms, optionally comprising one or more than one ethylenically unsaturated double bond, and optionally comprising one or more catenary nitrogen atoms, forming a cycle with the nitrogen atom which is connected thereto; and Cy′ represent a trivalent aliphatic group comprising at least 5 carbon atoms, optionally comprising one or more than one ethylenically unsaturated double bond, and optionally comprising one or more catenary nitrogen atoms, forming a cycle with the nitrogen atom which is connected thereto.

2. The fluoroelastomer composition according to claim 1, wherein said non-aromatic primary amines or amides are selected from the group consisting of: octadecylamine of formula CH.sub.3(CH.sub.2).sub.17—NH.sub.2; erucamide of formula H.sub.2N—C(O)—(CH.sub.2).sub.11—CH═CH—(CH.sub.2).sub.7CH.sub.3; oleamide of formula H.sub.2N—C(O)—(CH.sub.2).sub.7—CH═CH—(CH.sub.2).sub.7CH.sub.3; and hexamethylenediamine of formula H.sub.2N—(CH.sub.2).sub.6—NH.sub.2; and said cycloaliphatic secondary or tertiary amines are selected from the group consisting of: 1,8-diazabicycloundec-7-ene (DBU) of formula: ##STR00010##

3. The fluoroelastomer composition of claim 1, wherein the multifunctional compound is a bis-olefin (OF) selected from the group consisting of those complying with formulae (OF-1), (OF-2) and (OF-3): ##STR00011## wherein j is an integer between 2 and 10, and R1, R2, R3, R4, equal or different from each other, are H, F or C.sub.1-5 alkyl or (per)fluoroalkyl group; ##STR00012## 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; ##STR00013## wherein E, A and B have the same meaning as above defined; R5, R6, R7, equal or different from each other, are H, F or C.sub.1-5 alkyl or (per)fluoroalkyl group.

4. The fluoroelastomer composition of claim 3, wherein bis-olefin (OF) is a compound of formula (OF1), as above detailed.

5. The fluoroelastomer composition of claim 1, wherein fluoroelastomer (A) comprises iodine and/or bromine atoms in an amount of 0.001 to 10% wt, with respect to the total weight of fluoroelastomer (A).

6. The fluoroelastomer composition of claim 5 wherein the amount of iodine and/or bromine in fluoroelastomer (A) is of at least 0.05% wt, with respect to the total weight of fluoroelastomer (A).

7. The fluoroelastomer composition of claim 3, wherein fluoroelastomer (A) is selected from the group consisting of those having a backbone comprising: recurring units derived from TFE in an amount of 30 to 70% moles; recurring units derived from at least one perfluorinated monomer selected from the group consisting of PAVE monomers and MOVE monomers, as defined in claim 1, in an amount of 25 to 40% moles; recurring units derived from VDF in an amount of 1 to 25% moles; optionally, recurring units derived from ethylene (E) in an amount from 0 to 5% moles; optionally, recurring units derived from hexafluoropropylene (HFP) in an amount from 0 to 5% moles; optionally, recurring units derived from at least one bis-olefin (OF).

8. The fluoroelastomer composition of claim 1, wherein said organic peroxide is selected from the group consisting of di-tert-butyl peroxide; 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; bis(1,1-diethylpropyl)peroxide; bis(1-ethyl-1-methylpropyl)peroxide; 1,1-diethylpropyl-1-ethyl-1-methylpropyl-peroxide; 2,5-dimethyl-2,5-bis(tert-amylperoxy)hexane; dicumyl peroxide; dibenzoyl peroxide; di-tert-butyl perbenzoate; and bis[1,3-dimethyl-3-(tert-butylperoxy)butyl] carbonate.

9. The fluoroelastomer composition of claim 1, wherein fluoroelastomer the fluoroelastomers (A) is selected from the group consisting of fluoroelastomers having the following monomer compositions (in mol %): (i) tetrafluoroethylene (TFE) 40-65%, perfluoroalkyl vinyl ethers (PAVE) 20-50%, vinylidene fluoride (VDF): 10-25%; bis-olefin (OF): 0-5%; hexafluoropropylene (HFP): 0-5%; and (ii) tetrafluoroethylene (TFE) 40-65%, perfluoroalkyl vinyl ethers (PAVE) 20-45%, vinylidene fluoride (VDF): 10-25%; ethylene (E): 1-5%; bis-olefin (OF) 0-5%; hexafluoropropylene (HFP): 0-5%.

10. A method for fabricating a shaped article, the method comprising moulding, calendering, or extruding the fluoroelastomer composition of claim 1, such that a shaped article is fabricated.

11. The method according to claim 10, wherein the fluoroelastomer composition is fabricated into the desired shaped article, which is subjected to vulcanization during the processing itself and/or in a subsequent step.

12. A cured article obtained from the fluoroelastomer composition of claim 1.

13. The fluoroelastomer composition of claim 1, wherein the PAVE monomers are monomers of formula CF.sub.2═CFOR.sub.f1 in which R.sub.f1 is selected from —CF.sub.3, —C.sub.2F.sub.5, or —C.sub.3F.sub.7;

14. The fluoroelastomer composition of claim 1, wherein the MOVE monomers are monomers of formula CF.sub.2═CFOX.sub.0, in which X.sub.0 is (i) —C.sub.2F.sub.5—O—CF.sub.3; or (ii) a group of formula —CF.sub.2OR.sub.f2 in which R.sub.f2 is selected from —CF.sub.3, —C.sub.2F.sub.5, or —C.sub.3F.sub.7.

15. The fluoroelastomer composition of claim 3, wherein j is an integer between 4 and 8.

16. The fluoroelastomer composition of claim 3, wherein E is a —(CF.sub.2).sub.m— group, with m being an integer from 3 to 5.

17. The fluoroelastomer composition of claim 3, wherein the multifunctional compound is a bis-olefin (OF-2) of formula F.sub.2C═CF—O—(CF.sub.2).sub.5—O—CF═CF.sub.2.

18. The fluoroelastomer composition of claim 4, wherein bis-olefin (OF) is a compound of formula CH.sub.2═CH—(CF.sub.2).sub.n—CH═CH.sub.2, with n being an integer in the range of 4 to 6.

19. The fluoroelastomer composition of claim 6, wherein the amount of iodine and/or bromine in fluoroelastomer (A) is of at least 0.1% weight, with respect to the total weight of fluoroelastomer (A).

20. The fluoroelastomer composition of claim 6, wherein the amount of iodine and/or bromine in fluoroelastomer (A) is of at least 0.15% weight, with respect to the total weight of fluoroelastomer (A).

Description

[0105] The present invention will be now described in more detail with reference to the following examples, whose purpose is merely illustrative and not limitative of the scope of the invention.

Raw Materials

[0106] Fluoroelastomer A (FKM-A, herein after) is a VDF/TFE/perfluoromethylvinylether (MVE) having monomer composition, in moles %: 15% VDF/46% TFE/39% MVE; further comprising recurring units derived from a bis-olefin of formula CH.sub.2═CH—(CF.sub.2).sub.6—CH═CH.sub.2, and iodine cure sites, commercially available from Solvay Specialty Polymers Italy, S.p.A.

[0107] Fluoroelastomer B (FKM-B, herein after) is a VDF/TFE/MVE/ethylene (E) copolymer having monomer composition, in moles %: 38% VDF/30% TFE/10% HFP/18% MVE/4% E; further comprising recurring units derived from a bis-olefin of formula CH.sub.2═CH—(CF.sub.2).sub.6—CH═CH.sub.2, and iodine cure sites, commercially available from Solvay Specialty Polymers Italy, S.p.A.

[0108] Fluoroelastomer C (FKM-C, herein after) is a VDF/TFE/HFP fluoroelastomer, having monomer composition, in moles %: 70.5% VDF/11% TFE/18.5% HFP, further comprising recurring units derived from a bis-olefin of formula CH.sub.2═CH—(CF.sub.2).sub.6—CH═CH.sub.2, and iodine cure sites, commercially available from Solvay Specialty Polymers Italy, S.p.A.

Curing, Mechanical and Thermal Resistance Property Determination on Cured Samples

[0109] 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. The compression set (C-SET) has been determined on O-ring, specimen standard AS568A (type 214), according to the ASTM D 395, method B, either after 48 hours at 300° C., or after 70 hours at 280° C. Results are summarized in the following tables.

Tests Carried Out With FKM A and Basic Compound (B-1)

[0110] Curable compounds have been prepared mixing: [0111] 100 phr of FKM A; [0112] 1.2 phr of a bis-olefin of formula CH.sub.2═CH—(CF.sub.2).sub.6—CH═CH.sub.2; [0113] 1 phr of neat 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (C.sub.16H.sub.34O.sub.4), commercially available as LUPEROX® 101 from Akzo Nobel; [0114] 25 phr of Austin black (carbon black) commercially available from Coal Fillers Inc; [0115] and [0116] 0.5 phr or 1 phr of basic compound (B-1): octadecylamine of formula CH.sub.3(CH.sub.2).sub.17—NH.sub.2, commercially available as Armeen 18 D from Akzo Nobel.

[0117] Results summarized in Table 1 have been obtained by curing/molding specimens for 10 minutes at 170° C. and then post-curing the same for (8+16 hours) at 290° C.

TABLE-US-00001 TABLE 1 Amount of (B-1) C-Set 48 h @ C-Set 70 h @ Run in phr 300° C. (%) 280° C. (%) 1C 0 39 398 2 0.5 22 21 3 1.00 22 20

[0118] Data comprised in Table 1 clearly demonstrate that the addition of basic compound has a significant effect in improving C-set, i.e. sealing properties, at high temperatures.

Tests Carried Out With FKM-B and Basic Compound (B-1)

[0119] Curable compounds have been prepared mixing: [0120] 100 phr of FKM-B; [0121] as crosslinking agent, 4 phr of a bis-olefin (BO, herein after) of formula CH.sub.2═CH—(CF.sub.2).sub.6—CH═CH.sub.2 (examples 4C and 5C of comparison) or of triallylisocyanurate (TAIC) commercially available as DRIMIX® TAIC from Degussa (example 6C and 7C of comparison); [0122] 1.5 phr of neat 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (C.sub.16H.sub.34O.sub.4), commercially available as LUPEROX® 101 from Akzo Nobel; [0123] 30 phr of Austin black (carbon black) commercially available from Coal Fillers Inc; [0124] and [0125] 0 phr or 1 phr of basic compound (B-1): octadecylamine of formula CH.sub.3(CH.sub.2).sub.17—NH.sub.2, commercially available as Armeen® 18D from Akzo Nobel.

[0126] Results summarized in Table 2 have been obtained by curing/molding specimens for 10 minutes at 160° C. and then post-curing the same for (1+4 hours) at 230° C. in case of TAIC-containing compounds, or by curing/molding specimens for 10 minutes at 170° C. and then post-curing the same for (8+16 hours) at 290° C. in case of bis-olefin-containing compounds.

TABLE-US-00002 TABLE 2 Amount C-Set 48 h C-Set 70 h C-Set 70 h X-linking of (B-1) @ 300° C. @ 250° C. @ 200° C. Run agent in phr (%) (%) (%) 4C BO 0 >100 94 44 5C BO 1 >100 89 53 6C TAIC 0 >100 92 40 7C TAIC 1 >100 86 44

[0127] Data comprised in Table 2 clearly demonstrate that when the fluoroelastomer comprises an amount of recurring units derived from VDF exceeding 30% moles, the addition of basic compound has no noticeable effect in improving C-set, i.e. sealing properties, at high temperatures, or even said addition can provide for detrimental effect, as expected, because of the sensitivity of —CF.sub.2—CH.sub.2— units to aggressive basic environments.

Test Carried Out With FKM-C and (B-1)

[0128] Curable compounds has been prepared mixing: [0129] 100 phr of FKM-C; [0130] as cross-linking agent 1.5 phr of a bis-olefin (BO, herein after) of formula CH.sub.2═CH—(CF.sub.2).sub.6—CH═CH.sub.2 (Examples 8C and 9C of comparison) or 2.25 phr of triallylisocyanurate (TAIC) commercially available as DRIMIX® TAIC from Degussa (example 10C and 11C of comparison) [0131] 1.2 phr (Ex. 8C and 9C) or 1.0 phr of neat 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (C.sub.16H.sub.34O.sub.4), commercially available as Luperox® 101 liquid from Akzo Nobel; [0132] 30 phr of carbon black N990 MT commercially available from Cancarb; and [0133] variable amount (0 or 1 phr) of (B-1).

[0134] Results summarized in Table 3 have been obtained by curing/molding specimens for 10 minutes at 170° C. and then post-curing the same for (8+16 hours) at 290° C. for compounds comprising bis-olefin (Ex. 8C and 9C), and by curing/molding specimens for 10 minutes at 170° C. and then post-curing the same for (1+4 hours) at 230° C. for compounds comprising TAIC (Ex. 10C and 11C).

TABLE-US-00003 TABLE 3 Cross- Amount linking of (B-1) C-Set 48 h @ C-Set 70 h @ Run agent in phr 300° C. (%) 200° C. 8C BO 0 47 9C BO 1 50 10C TAIC 0 27 11C TAIC 1 48

[0135] Data summarized in Table 3 further confirm that, when a fluoroelastomer is used comprising an amount of VDF exceeding 30% by moles, there is no advantageous effect in adding the basic compound; even, a detrimental effect can be shown, in particular when using TAIC as crosslinking agent.