Fluoroelastomer compositions

Abstract

The invention pertains to a (per)fluoroelastomer composition comprising: a (per)fluoroelastomer [fluoroelastomer (A)]; and at least one (per)fluoropolyether additive [polymer (E)] comprising a (per)fluoropolyether chain comprising recurring units having at least one catenary ether bond and at least one fluorocarbon moiety, and comprising at least one chain end comprising at least one per(halo)fluorinated aromatic group [group (Ar.sup.F)], said polymer (E) being comprised in the composition in an amount of 0.5 to 30 phr, with respect to fluoroelastomer (A).

Claims

1. A (per)fluoroelastomer composition (C) comprising: a fluoroelastomer (A), wherein fluoroelastomer (A) is a (per)fluoroelastomer; and at least one polymer (E), wherein polymer (E) is a (per)fluoropolyether additive comprising a (per)fluoropolyether chain comprising recurring units having at least one catenary ether bond and at least one fluorocarbon moiety, and comprising at least one chain end comprising at least one per(halo)fluorinated aromatic group (Ar.sup.F) as a terminal group, said polymer (E) being comprised in composition (C) in an amount of 0.5 to 30 phr, with respect to fluoroelastomer (A).

2. The composition (C) of claim 1, wherein fluoroelastomer (A) is selected from: (1) vinylidene fluoride (VDF)-based copolymers, in which VDF is copolymerized with at least one comonomer 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 fluoroolefins comprising at least one of iodine, chlorine and bromine; (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 one or more catenary oxygen atoms; (f) (per)fluorodioxoles having formula: ##STR00010## wherein each of R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6, equal to or different from each other, is independently selected from the group consisting of fluorine atom and C.sub.1-C.sub.6 (per)fluoroalkyl groups, optionally comprising one or more than one oxygen atom; (g) (per)fluoro-methoxy-vinylethers (MOVE, hereinafter) having formula:
CF2CFOCF.sub.2OR.sub.f2 wherein R.sub.f2 is selected from the group consisting of C.sub.1-C.sub.6 (per)fluoroalkyls; C.sub.5-C.sub.6 cyclic (per)fluoroalkyls; and C.sub.2-C.sub.6 (per)fluorooxyalkyls, comprising at least one catenary oxygen atom; (h) C.sub.2-C.sub.8 non-fluorinated olefins (O1); (i) ethylenically unsaturated compounds comprising nitrile (CN) groups, optionally (per)fluorinated; or (2) TFE-based copolymers, in which TFE is copolymerized with at least one comonomer selected from the group consisting of (c), (d), (e), (g), (h) and (i) as above detailed.

3. The composition (C) of claim 2, wherein-vinylidene fluoride (VDF)-based copolymers, in which VDF is copolymerized with at least one comonomer selected from the group consisting of: tetrafluoroethylene (TFE); hexafluoropropylene (HFP); vinyl fluoride (VF); trifluoroethylene (TrFE); hexafluoroisobutene (HFIB); perfluoroalkyl ethylenes of formula CH.sub.2CHR.sub.f wherein R.sub.f is a C.sub.1-C.sub.6 perfluoroalkyl group; chlorotrifluoroethylene (CTFE); (per)fluoroalkylvinylethers (PAVE) of formula CF.sub.2CFOR.sub.f wherein R.sub.f is CF.sub.3, C.sub.2F.sub.5, or C.sub.3F.sub.7; (per)fluoro-oxy-alkylvinylethers of formula CF.sub.2CFOX, wherein X is a perfluoro-2-propoxypropyl group; (per)fluorodioxoles having formula: ##STR00011## wherein each of R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6, equal to or different from each other, is independently selected from the group consisting of CF.sub.3, C.sub.2F.sub.5, C.sub.3F.sub.7, OCF.sub.3, and OCF.sub.2CF.sub.2OCF.sub.3; (per)fluoro-methoxy-vinylethers having formula: CF.sub.2CFOCF.sub.2OR.sub.f2 wherein R.sub.f2 is selected from CF.sub.2CF.sub.3, CF.sub.2CF.sub.2OCF.sub.3, or CF.sub.3; ethylene; and propylene.

4. The composition (C) of claim 1, wherein fluoroelastomer (A) comprises recurring units derived from a bis-olefin (OF), wherein bis-olefin (OF) is of the 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 or C.sub.1-C.sub.5 alkyl; Z is a linear or branched C.sub.1-C.sub.18 hydrocarbon radical, optionally containing oxygen atoms, and optionally fully or partially fluorinated, or a (per)fluoropolyoxyalkylene radical.

5. The composition (C) of claim 4, wherein fluoroelastomer (A) is selected from VDF-based copolymers comprising (with respect to total moles of recurring units of fluoroelastomer (A)): from 5 to 35% moles of recurring units derived from at least one (per)fluoro-methoxy-vinylethers (MOVE) having formula:
CF.sub.2CFOCF.sub.2OR.sub.f2 wherein R.sub.f2 is selected from the group consisting of C.sub.1-C.sub.6 (per)fluoroalkyls; C.sub.5-C.sub.6 cyclic (per)fluoroalkyls; and C.sub.2-C.sub.6 (per)fluorooxyalkyls, comprising at least one catenary oxygen atom; from 0.5 to 35% moles of recurring units derived from at least one C2-C8 perfluoroolefin; with the provisio that the sum of recurring units derived from (per)fluoro-methoxy-vinylethers (MOVE) and from the perfluoroolefin is of at least 10% moles; from greater than 0 to 5% moles of recurring units derived from bis-olefin (OF); and from 90 to 30% moles of recurring units derived from VDF.

6. The composition (C) of claim 5, wherein fluoroelastomer (A) is selected from VDF-based copolymers comprising (with respect to total moles of recurring units of fluoroelastomer (A)): from 15 to 25% moles of recurring units derived from at least one (per)fluoro-methoxy-vinylethers (MOVE) having formula:
CF.sub.2CFOCF.sub.2OR.sub.f2; from 2 to 25% moles of recurring units derived from at least one C.sub.2-C.sub.8 perfluoroolefin; with the provisio that the sum of recurring units derived from (per)fluoro-methoxy-vinylethers (MOVE) and from the perfluoroolefin is of at least 17% moles; from greater than 0 to 2.5% moles of recurring units derived from bis-olefin (OF); and from 83 to 50% moles of recurring units derived from VDF.

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

8. The composition (C) of claim 1, wherein the (per)fluoropolyoxyalkylene chain of polymer (E) is a chain comprising a plurality of recurring units (R.sub.1), said recurring units having general formula: (CF.sub.2).sub.kCFZO, wherein k is an integer of from 0 to 3 and Z is selected from a fluorine atom or a C.sub.1-C.sub.6 perfluoro(oxy)alkyl group.

9. The composition (C) of claim 8, wherein polymer (E) complies with formula:
T-OR.sub.f-T(I) wherein: R.sub.f is a (per)fluoropolyoxyalkylene chain comprising a plurality of recurring units (R1), said recurring units having general formula: (CF.sub.2).sub.kCFZO, wherein k is an integer of from 0 to 3 and Z is selected from a fluorine atom or a C.sub.1-C.sub.6 perfluoro(oxy)alkyl group; each of T and T, equal to or different from each other, are selected from: a group of any of formulae CF.sub.3, CF.sub.2C.sub.1, CFZ*CH.sub.2OH, CFZ*COOH, CFZ*COOR.sub.h and CFZ*CH.sub.2(OCH.sub.2CH.sub.2).sub.kOH, wherein k is an integer ranging from 0 to 10, Z* is F or CF.sub.3; and R.sub.h is a hydrocarbon chain; or a group (Ar.sup.F) of formula CFZ**CH.sub.2(OCH.sub.2CH.sub.2).sub.kOAr.sup.F, wherein k is an integer ranging from 0 to 10, Z** is F or CF.sub.3; and Ar.sup.F is a perfluoroaromatic group; with the provisio that at least one of T and T is a group (Ar.sup.F).

10. The composition of claim 9, wherein polymer (E) complies with formula:
T*-O(CF.sub.2CF.sub.2O).sub.a(CFYO).sub.b(CF.sub.2CFYO).sub.c(CF.sub.2O).sub.d(CF.sub.2(CF.sub.2).sub.zCF.sub.2O).sub.e-T*, wherein: Y is a C.sub.1-C.sub.5 perfluoro(oxy)alkyl group; z is 1 or 2; a, b, c, d, e are integers0; each of T* and T*, equal to or different from each other, are selected from: a group of any of formulae CF.sub.3, CF.sub.2C.sub.1, CFZ*CH.sub.2OH, CFZ*COOH, CFZ*COOR.sub.h and CFZ*CH.sub.2(OCH.sub.2CH.sub.2).sub.kOH, wherein k is an integer comprised ranging from 0 to 10, Z* is F or CF.sub.3; and R.sub.h is a hydrocarbon chain; or a group (Ar.sup.F) of formula CFZ**CH.sub.2(OCH.sub.2CH.sub.2).sub.kOAr.sup.F, wherein k is an integer ranging from 0 to 10, Z** is F or CF.sub.3; and Ar.sup.F is a perfluoroaromatic group; with the provisio that at least one of T and T is a group (Ar.sup.F).

11. The composition (C) according to claim 1, said composition (C) further comprising at least one peroxide.

12. The composition (C) of claim 11, said composition (C) comprising one or more ingredients selected from the group consisting of: (a) polyunsaturated curing coagents, in amounts of from 0.5 to 10 phr, relative to 100 weight parts of fluoroelastomer (A); (b) metallic basic compounds, in amounts of from 0.5 to 15 phr, relative to 100 weight parts of fluoroelastomer (A); (c) acid acceptors which are not metallic basic compounds, in amounts of from 0.5 to 15 phr, relative to 100 weight parts of fluoroelastomer (A); and (d) other conventional additives.

13. The composition (C) of claim 12, said composition (C) comprising one or more ingredients selected from the group consisting of: (a) polyunsaturated curing coagents, in amounts of from 1 to 7 phr, relative to 100 weight parts of fluoroelastomer (A); (b) metallic basic compounds selected from the group consisting of (j) oxides or hydroxides of divalent metals, and (jj) stearates, benzoates, carbonates, oxalates or phosphites of Ba, Na, K, Pb, or Ca, in amounts of from 1 to 10 phr, relative to 100 weight parts of fluoroelastomer (A); (c) acid acceptors selected from nitrogen-containing organic compounds, in amounts of from 1 to 10 phr, relative to 100 weight parts of fluoroelastomer (A); and (d) fillers, thickeners, pigments, antioxidants, stabilizers, or processing aids.

14. The composition (C) according to claim 11, wherein the peroxide is selected from organic peroxides; dialkyl peroxides; di-tert-butyl peroxide; 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; dicumyl peroxide; dibenzoyl peroxide; di-tert-butyl perbenzoate; bis [1,3-dimethyl-3-(tert-butylperoxy)butyl] carbonate; or mixtures thereof.

15. The composition (C) according to claim 1, said composition (C) further comprising at least one curing agent; at least one accelerator or a combination thereof, wherein the amount of accelerator(s) is comprised between 0.05 and 5 phr, relative to 100 weight parts of fluoroelastomer (A); and the amount of the curing agent is between 0.5 and 15 phr, relative to 100 weight parts of fluoroelastomer (A).

16. The composition (C) according to claim 15, further comprising at least one ingredient selected from the group consisting of: i) one or more mineral acid acceptors selected from the group consisting of divalent metal oxides, comprised in amounts of 1 to 40 parts per 100 parts of fluoroelastomer (A); ii) one or more basic compounds selected from the group consisting of Ca(OH).sub.2, Sr(OH).sub.2, Ba(OH).sub.2, metal salts of weak acids and mixtures thereof in amounts of from 0.5 to 10 parts per 100 parts of fluoroelastomer (A).

17. The composition (C) according to claim 1, wherein fluoroelastomer (A) comprises recurring units derived from ethylenically unsaturated compounds comprising nitrile groups, optionally (per)fluorinated and wherein composition (C) further comprises at least one of (i) organotin compounds; (ii) aromatic amine compounds; (iii) bisamidrazones; or (iv) bisamidoximes.

18. A cured article obtained by moulding and curing composition (C) according to claim 1, wherein the cured article is selected from the group consisting of O(square)-rings, packings, gaskets, diaphragms, shaft seals, valve stem seals, piston rings, crankshaft seals, cam shaft seals, oil seals, piping and tubing.

19. A method for processing the composition (C) according to claim 1, wherein the method comprises at least one of injection moulding, compression moulding, extrusion moulding, coating, screen printing technique, or form-in-place technique the composition (C) of claim 1.

20. The composition (C) according to claim 1, said composition (C) further comprising at least one curing agent selected from the group consisting of aromatic or aliphatic polyhydroxylated compounds, and derivatives thereof; at least one accelerator selected from the group consisting of 1) quaternary ammonium or phosphonium salts; (2) aminophosphonium salts; (3) phosphoranes; and (4) imine compounds of formula [Ar.sub.3PNPAr.sub.3].sup.+.sub.nX.sup.n, wherein Ar is an aryl group, n is an integer of 1 or 2 and X is a n-valent anion, or of formula [(R.sub.3P).sub.2N].sup.+X.sup., wherein R is an aryl or an alkyl group, and X is a monovalent anion; or a combination thereof, wherein the amount of accelerator(s) is comprised between 0.05 and 5 phr, relative to 100 weight parts of fluoroelastomer (A); and the amount of the curing agent is between 1 and 6 phr, relative to 100 weight parts of fluoroelastomer (A).

Description

EXAMPLES

(1) TECNOFLON VPL X75545 FKM is a peroxide-curable iodine end group-containing fluoroelastomer, comprising recurring units derived from vinylidene fluoride (VDF) 60.5% by moles; tetrafluoroethylene (TFE) 17.5% by moles; and perfluoro-methoxy-vinylethers having formula CF.sub.2CFOCF.sub.2OCF.sub.3 (MOVES) 22% by moles(FKM-1), commercially available from Solvay Specialty Polymers Italy S.p.A.

Preparative Example 1: Preparation of a Hexafluorobenzene Derivative of PFPE Diol [PFPE-Ar.SUP.F.-1]

(2) A PFPE diol precursor [PFPE-1] having the following structure: HOCH.sub.2CF.sub.2O(CF.sub.2O).sub.e(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O).sub.e(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.qCF.sub.2CH.sub.2OH

(3) wherein n=4.90, m=4.75, and (p+q)=0; the number average molecular weight (M.sub.n) of the (per)fluoropolyether chain is equal to 1060 Dalton was used.

(4) 100 g of the PFPE-1 were mixed with 70 g of hexafluorobenzene (from Sigma-Aldrich) and 16 g of KOH powder (title 85%) were added to the liquid mixture at room temperature. The reaction mass was kept, under stirring, at 60 C. for 6 hours. The resulting solution was washed two times with aqueous HCl (0.1N) and dried at reduced pressure resulting 125.7 g of colourless liquid product. The .sup.19F NMR analysis showed a total conversion (>99% by mol) of the CF.sub.2CH.sub.2OH groups to the correspondent aromatic derivative CF.sub.2CH.sub.2OC.sub.6F.sub.5.

Preparative Example 2: Preparation of a Hexafluorobenzene Derivative of PFPE Diol [PFPE-Ar.SUP.F.-2]

(5) A PFPE diol precursor [PFPE-2] having the following structure: HOCH.sub.2CF.sub.2O(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.qCF.sub.2CH.sub.2OH wherein n=6.27, m=8.03, and (p+q)=0.09; the number average molecular weight (M.sub.n) of the (per)fluoropolyether chain is equal to 1540 Dalton, was used.

(6) 100 g of the PFPE-2 were mixed with 50 g of hexafluorobenzene (from Sigma-Aldrich) and 11 g of KOH powder (title 85%) was added to the liquid mixture at room temperature.

(7) The reaction mass was kept, under stirring, at 60 C. for 6 hours.

(8) The resulting solution was washed two times with aqueous HCl (0.1N) and dried at reduced pressure resulting 118.4 g of colourless liquid product. The .sup.19F NMR analysis showed a total conversion (>99% by mol) of the CF.sub.2CH.sub.2OH groups to the correspondent aromatic derivative CF.sub.2CH.sub.2OC.sub.6F.sub.5.

Preparative Example 3: Preparation of Hexafluorobenzene Derivative of PFPE [PFPE-Ar.SUP.F.-3]

(9) A PFPE diol precursor [PFPE-2] having the following structure:
TO(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q-T

(10) T and T are end groups CF.sub.2CH.sub.2(OCH.sub.2CH.sub.2).sub.kOH

(11) wherein n=4.29, m=5.19, and (p+q)=0.06; the number average molecular weight (M.sub.n) of the (per)fluoropolyether chain is equal to 1200 Dalton, was used.

(12) 100 g of the PFPE diol were mixed with 65 g of hexafluorobenzene (from Sigma-Aldrich) and 14 g of KOH powder (title 85%) was added to the liquid mixture at room temperature.

(13) The reaction mass was kept, under stirring, at 60 C. for 6 hours.

(14) The resulting solution was washed two times with aqueous HCl (0.1N) and dried at reduced pressure resulting 122.3 g of colourless liquid product. The .sup.19F NMR analysis showed a total conversion (>99% by mol) of the CH.sub.2CH.sub.2OH groups to the correspondent aromatic derivative CH.sub.2CH.sub.2OC.sub.6F.sub.5.

(15) General Compounding and Curing Procedure

(16) FKM-1 was compounded with the ingredients as detailed below in a open mill. Plaques were cured in a pressed mould for 5 minutes at 160 C. and then post-treated in an air circulating oven in conditions (1+4 hours at 230 C.).

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

(18) TS is the tensile strength in MPa;

(19) M.sub.100 is the modulus in MPa at an elongation of 100%;

(20) EB 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) Compression set (C-Set) values have been determined on O-rings (#214 class) according to the ASTM D395-B method (70 hours at 200 C.). Glass transition temperature (T.sub.g) of cured specimens was determined according to ASTM D3418.

(23) Curing recipe and conditions and properties of cured sample are summarized, respectively, in tables 1 and 2.

(24) TABLE-US-00001 TABLE 1 Ingredient Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5C Ex. 6C FKM-1 wt parts 100 100 100 100 100 100 PFPE-Ar.sup.F-1 phr 10.00 20.00 PFPE-Ar.sup.F-2 phr 20.00 PFPE-Ar.sup.F-3 phr 20.00 PFPE-1 phr 20.00 Peroxide.sup.1 phr 2.00 2.00 2.00 2.00 2.00 2.00 TAIC.sup.2 phr 5.00 5.00 5.00 5.00 5.00 5.00 C-black.sup.3 phr 30.00 30.00 30.00 30.00 30.00 30.00 Zinc Oxide.sup.4 phr 5.00 5.00 5.00 5.00 5.00 5.00 .sup.145% active dispersion of 2,5-dimethyl-2,5-di-t-butyl-peroxy-hexane in calcium carbonate, commercially available from Arkema under tradename Luperox 101XL 45; .sup.2Triallyl isocyanurate (75%) dispersion in silica, commercially available as Drimix TAIC 75 from Finco; .sup.3C-black N990 MT from Cancarb; .sup.4ZnO ReagentPlus from Sigma Aldrich.

(25) TABLE-US-00002 TABLE 2 Sample Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5C Ex. 6C Mixing.sup.5 (a.u.) good good good good n.a. bad TS (MPa) 12.2 10.5 13.0 12.5 12.0 13.4 M.sub.100 (MPa) 2.1 2.6 3.7 2.5 5.7 2.8 E.B. (%) 256 142.0 195.0 226.0 160 253.0 HDS Shore A 55 53.0 61.0 57.0 68 59.0 C-Set (%) 24.0 24.8 21.3 24.3 19.6 27.0 Tg ( C.) 52.0 53.0 50.0 54.0 46.0 46.0 .sup.5a.u. = arbitraty unit - Good: No oil traces on the surface of formulated slab nor on the surface of cured items; Bad: traces of oil on the surface of formulated slab and on the surface of cured items; n.a.: not applicable.

(26) Data above recollected well demonstrate that the addition of polymer (E) in above mentioned amounts is effective in providing cured parts having outstanding low temperature behaviour, with a gain of 6 to 8 C. towards lower temperatures in terms of Tg, which is of high significance in this field, while maintaining substantially unchanged mechanical properties and favourable sealing performances.

(27) The addition of a perfluoropolyether deprived of a perfluoroaromatic group is significantly adversely affecting the sealing properties, without providing any significant gain in low temperature behaviour.