MXPA96004995A - Compositions fluoroelastomeri - Google Patents

Abstract

A curing system for fluoroelastomers curable by the peroxidic route, which comprises iodine which comprises as the curing agent a bis-olefin having the formula (See Formula) wherein R 1, R 2, R 3, R 4, R 5 and R 6 or different from each other, are H or C 1 -C 6 alkyl, Z is a straight or branched C 1 -C 18 alkylene or cylcoalkylene radical, optionally containing oxygen atoms, preferably at least partially fluorinated, or a radical (per) fluoropolyoxyalkylene

Description

COMPOSITIONS FLUQROELASTOMERICAS DESCRIPTION OF THE INVENTION The present invention relates to new flush-flow composites having improved thermal resistance at high temperatures. It is known that the curing of the luoroelastomers can be carried out ionically and by peroxides. In ionic curing, suitable curing agents, for example polyhydroxy compounds such as bisphenol AF, in association with accelerators such as for example tetraalkylammonium salts, phosphome or inophosphonium, are added to the fluoro elastomer. In the peroxidic cure, the polymer must contain healing sites capable of forming radicals in the presence of peroxide. Therefore, the site-cured monomers containing iodine and / or bromine are introduced into the chain, as described for example in U.S. Patent 4,035,565, U.S. 4,475,165 and EP 199,136, or in an alternative for the system indicated or at the same time in the polymerization phase, chain transfer agents containing iodine and / or bromine can be used, which produce iodinated and / or brominated end groups, see for example the United States Patent 4, 243, 770 and US 5,173,553. Healing by the peroxidic route is carried out, according to techniques known by the addition of peroxides capable of generating radicals by heating, for example dialkyl peroxides, such as di-terbuperived / 2,5-di et i 1 -2, 5-di (terbut? Lpero i) hexane, etc. Then other products are added to the curing mixture, such as: curative coagents among which the most commonly used is triallyl cyanurate and preferably triallyl isocyanurate (TAIC), etc .; a metallic compound, in amounts consisting of between 1 and % by weight with respect to the selected polymer of divalent metal oxides or hydroxides, such as for example lg, Ca, etc.; other conventional additives, such as mineral fillers, pigments, binders, stabilizers and the like. The ionically cured luoroelastomers, compared to the luoraelastomers cured by the peroxidic route, are more stable when subjected to high temperatures (higher thermal resistance at high temperatures). As a matter of fact, by ionic curing, the cured products are obtained which maintain good final properties, in particular thermal resistances also at temperatures higher than 250 ° C. The f luoroelastómeros cured by the peroxidic route can be used, for example, up to 230 ° C as at higher temperatures show a clear loss of mechanical properties, in particular the elongation at break reaches greater variations of 100%. The peroxidic cure does not, therefore, give f luoroelastomers that have a thermal resistance greater than 230 ° C. However, the disadvantage of ionic curing is that hand-made articles show less chemical resistance compared to those obtained by peroxide cure. In addition, f luoroelastomers having high fluorine content, in general without the presence of VDF units in the polymer can not be ionically cured. Therefore, in the application fields where a high chemical resistance combined with a high thermal resistance at high temperatures, at a higher than 300 ° C, are required, it was felt the need to have cured articles available that allow this combination of properties . An object of the present invention is the obtaining of the luorostromeric materials having improved thermal resistance at high temperatures, greater than 250 ° C or more in the f luoroelastomers cured by the peroxide route, which contain iodine. It is well known that there is a great demand for f luoroeslastomers which have, for a wide variety of applications, high chemical resistance combined with high thermal resistance at high temperatures. For example, joints and seal rings for applications for which both good chemical resistance / thermal resistance are required also at high temperatures, greater than 20 ° C. preferably greater than 250 ° C or 300 ° C. Surprisingly and unexpectedly it has been found that it is possible to find a solution to the technical problem described in the above, if a particular healing system is used as described in the following. An object of the present invention is a curing system for fluoro elastomers curable by the peroxidic route, which comprises iodine which comprises as a curing agent a bis-olefin having the general formula: RiRas C = C -Z- C = CRsR ^ (I) II where: R ,, Ra ,, R3, Rt +, R.3, R ¿, equal or different from each other, are H or C ^ -C3 alkyl, linear or branched when possible; Z is a linear or branched alkylamino radical of 0 ° -0 ° C which optionally contains oxygen atoms, preferably at least partially fluorinated or a (per) -fluoroxy-organic radical. In the formula (I), Z is preferably a perfluoroalkylenic radical of C. + - C12, more preferably C + - r ?, while Rt, Rg ,, R, Rt ,, R? P ?, are preferably hydrogen. When Z is a radical (per) f luoropol I-alkaline it may consist of units selected from the following: -CFaCFaO-, -CFaCF (CF3) 0-, -CFX.O- where * - K, GF-, -CFa-CF ^ CF ^ O-, -CF ^ -CF- ^ CH ^ O-, -C, F40-. Preferably, Z has the formula: - () p-CFaO- (CFS2CFa! 0) m (CF: 20) r - CF? A- (Q) p- (II) in which: it is an alkylene or oxyalkylenic radical of C ± - p is 0 or 1; m and n are such numbers that the m / n ratio is between 0.2 and 5 and the molecular weight of the luoropolioxyalkylene radical (per) f is between 500 and 10,000, preferably between 1000 and 4000. Preferably Q is selected from: -CH-BOCH »-; -CH2OCH2CH6) ßCH2-, wherein s is an integer 1 to 3. The bis-olefms of the formula (I) in which Z is an alkylene or cycloalkylene radical, can be prepared in accordance with those described, for example by IL nunyants et al ín Izv. Akad. Nauk SSSR, Being him-, 1964 (2), 364-6, although bis-olefins containing (per) f-luo-polyoxyalkylenic sequences are described in US Pat. No. 3,610,674. The amount of curing agent is that sufficient for curing, which is generally between 0.5-10% by weight with respect to the polymer, preferably 1-5% by weight. The fluoro elastomers curable by the peroxidic route according to the present invention are preferably those containing iodine as the radical attack site. F luoroelastomers containing iodine, as already mentioned, are known products. They contain iodine in amounts generally comprised between 0.001 and 5% by weight, preferably between 0.01 and 2.5% by weight with respect to the total weight of the polymer. The iodine atoms may be present at ID long of the chain and / or at the terminal position. To introduce the iodine atoms along the chain, the copolyzing of the basic monomers of the fluoro elastomer is carried out with a suitable fluorinated comonomer containing iodine, a curative monomer at the site, see for example the Patent of the United States 4,745,165, US-4,631,065, and US-4, 214,060, European patent 95107005.1. Such a comonomer can be selected for example from: (a) iodo (per) f luoroalkyl 1-perfluorovinyl ethers of the formula: I- ^ -O-CF ^ Fa (III) wherein R t is a (per) f-luoroalkylene of Ct-C12, optionally containing chlorine atoms and / or ethereal oxygen; for example: ICFa-0-CF = CF.3 ICFaCFa? -0-CF = CF s », I Fs, CFa, CF-0-CF = CF12, CFaCFICFa.-O-CF-CFJB, and the like. (b) ioda- (per) f luoroolef inas of the formula: wherein R '? it is a (per) f luoralquinone of CA ~ Cxa !, which optionally contains chlorine atoms; for example: iodotr íf luoroet i leño, l-iodo-2, 2-dif luoroe i leño, iodo-3, 3,, -tetraf luorobuteno-1, 4-iodo-perf luorobuteno-1, / similars, (c) iodine- (per) f luoroolef inas of the formula: CHRßBCH-ZßCHaCHRß-I (V) wherein R0 is H or -CH3; Za is a (per) f-luoroalkylene radical of C ± -C x e > , linear or branched, optionally containing 1 or more oxygen atoms or a (per) f luoropolyoxyalkyl radical as defined above. In an alternative or in addition to the iodinated comonomer, the luoroelastomer may contain iodine atoms in the terminal position, which is derived from a suitable iodinated chain transfer agent, introduced into the reaction medium during the preparation of the polymer, as described in U.S. Patent 4,501,669. Such transfer agents have the formula R, (I), wherein Rt is a (per) f-luo-alkyl radical or chlorofluoroalkyl 1-Ct-C12, optionally containing chlorine atoms, while X is 1 or 2 They can be selected, for example from: CFaI, 2 (CFa) 6I, I <; CFa.)? ". I, CFjj.CH, CF3CFICFZI and the like. The amount of iodine in the terminal position is generally between 0.001 and 3%, preferably between 0.01 and 1% by weight with respect to the weight of the luoroelastomer. See USP 4,035,565 and USP 4,694,045. Others who were involved in curative healing at the site are ludoalkeroalkine and lteters, see USP 4,745,165 and USP 4,564,662. For the iodine introduced as the end of the chain by the addition of iodinated chain transfer agents as indicated in the above, see for example, US Pat. Nos. 4,243,770 and US-4, 943, 622. It is also possible to introduce iodine as the end of the chain using alkaline or alkaline earth metal iodides, as described in Patent Application EP 407,937. In combination with chain transfer agents containing iodine, other chain transfer agents known in the art, such as ethyl acetate, diethyl algonate, etc., can be used. In addition, the f luoroelastomers curable by the peroxidic route may also contain bromine, both in the chain and in the terminal position. However, it substantially does not take part in the healing. The bromine in the chain can be introduced according to known techniques, see for example USP 4,035,565, USP 4,745,165, EP 199,136; or as terminal bromine, see USP 4,501,669. It has also been found that in addition to the bis-olefins, the curing agents of the invention, apart from the non-curing agents, can be added, preferably TAIC. It has been observed that small amounts of TAIC lead to an improvement of the general properties obtainable by the bis-olefin alone, such as thermal stability and mechanical properties. This will be apparent from the following illustrative examples.

The luoroelastomers are TFE or copolymers of vimlidene fluoride (VDF) and at least one fluorinated olefin which has a terminal unsaturation, which contains at least one fluorine atom in each carbon atom of the double bond, the other atoms can it is fluorine, hydrogen, f luoroalkyl or fluoroalkoxy of 1 to 10 carbon atoms, preferably 1-4 carbon atoms. In particular, the basic structure of the luoroelastomer may be selected from: (1) the VDF-based copolymers, in which the latter is copolymesed with at least one comonomer selected from: perfluoroalfanes of Cj, -C ?, as tetraf luoroe i lena (TFE), hexaf luoropropene (HFP); chloro- and / or bromine and / or iodo-f luoroolefins of C2-C ?, such as chlorotropyl luoraethylene (CTFE) and bromotropic luoroethanol; (per) f luoroalkyl vinyl ethers (PAVE) CF 2 = CF 0 Rf, wherein R x is a (per) f luoroalkyl of for example tpf luoromet lyo, bro odi f luoramethyl pentaf luoropropyl; per f lurooxalkylvinylleters, wherein X is a perfluorooxyalkyl of Ct.-C112 having one or more ether groups, for example perf luoro-2-propox? -prop? the; fluorine-free olefins (01) of C2-Cß, for example ethylene and propylene; (2) TFE-based copolymers, which are preferred according to the present invention, in which TFE is copolymer with at least one comonomer selected from: (per) fluroalkinevinters (PAVE) CFa = CF0R1 P? which R £ has the meaning of * '; perf luoro-o íalqu i lvim léters CFa = CF0X, where X is defined as above, f luroroolef inas of C2-C? containing hydrogen and / or chlorine and / or bromine and / or iodine atoms; olefins without fluoro (01) of C3-Cß. Within the classes defined in the above, the preferred basic monomeric compositions are the following (% in evils): (a) VDF of 45-65%, HFP of 15-45%, TFE of 0-30%; (b) VDF of 50-60%, PAVE of 5-50%, TFE of 0-20%; (c) VDF of 20-30%, 01 of 10-30%, HFP and / or PAVE of 16-27%, TFE of 10-30%; (d) TFE of 50-60%, PAVE of 20-50%; (e) TFE of 45-65%, 01 of 20-55%, VDF of 0-30%; (f) EFE of 32-60%, 01 of 10-40%, PAVE of 20-40%. The luoroelastomers may also contain monomer units in the chain, which are derived from small amounts of a bis-olefin (I) as described in European Patent Application No. 94120504.9, generally 0.01-1% by moles with respect to the polymer. Other f luoroelastomers, which can be used are those having a high fluorine content, which have, for example, the following composition: - 33-75% by moles of full tetraf luoroet (TFE), preferably 40- 60%; - 15-45% by moles of a perfluorovinyl ether (PVE), preferably 20-40%; - 10-22% by moles of vimlidene fluoride (VDF), preferably 15-20%. The PVE has the formula: f .. with R f .. = -perf luoroalkyl of Cl-Crt ,, preferably of C, - r., Or containing one or more ethereal groups C2-C9. The iodinated polymers indicated in the above are commercially known, for example as: DAIELR G902 and Perfluoro DAIEL * by Daikin Industries, TecnoflonR PFR 94 by Ausimont. Healing by the peroxidic route is carried out, according to known techniques, by the addition of peroxides capable of generating radicals by heating. Among the most commonly used peroxides, mention may be made of: Dialkylperoxides such as, for example, di-tert-butyl-peroxide and 2,5-dimet-1-2, 5-d? (terbutylperoxy) -hexane; dicuyl peroxide; dibenzoyl peroxide; diterbutyl perbepzaate; diCl, 3-d? et i 1-3- (terbut ílpero i) but? ID-carbonate. Other peroxide systems are described, for example, in the European patent applications EP 136,596 and EP 410,351. Other products can then be added to the curing mixture, such as: (a) optionally other curing coagents, in addition to those of the invention, in amounts generally consisting of between 0.1 and 3%, preferably between 0.1 and 1 % by weight with respect to the polymer; Among those commonly used are: tpalil cyanurate; tpalyl isocyanide (TAIC); tr? s (d? al i lamina) -s-tr i az ina; tpalil phosphite; N, N-d? Al i 1-acr i lick, N,, N ',' -tetral and 1-malonam? Da; tpvinyl isocyanurate; 2,4,6-trichino-1-methylspsinoxane, etc., particularly preferred is TAIC; (b) a metal compound, in amounts comprised between 1 and 15%, preferably between 2 to 10% by weight with respect to the polymer, selected from oxides or hydroxides of divalent metals, such as for example Mg, Zn, Ca or Pb , optionally combined with a salt of a weak acid, such as, for example, stearates, benzoates, carbonates, oxalate or phosphites of Ba, Na, t-, Pb, Ca; (c) other conventional additives, such as reinforcing fillers, pigments, anti-oxidants, stabilizers and the like. The preparation of the fluoroplastomers object of the present invention can be carried out by copolymeation of the monomers in aqueous emulsion according to methods well known in the art, in the presence of radical initiators (for example persulfates, perfosphates, peborates or alkali or ammonium carbonates or percarbonates, optionally with iron or silver salts or other readily oxidizable metals, surfactants such as, for example, (per) fluoroalkyl (eg perfluoroacetapanedium ammonium) carboalkylates or sulfonates; Lutronic oxyoxyalkyls, or others known in the art, are also present in the reaction medium.When the polymerization is terminated, the luoroelastomer is isolated from the emulsion by conventional methods, such as coagulation by the addition of electrolytes. or by cooling, Alternatively, the polymerization reaction can be carried out in bulk or in suspension, in a organic liquid where a radical initiator, suitable in accordance with well known techniques is present. The polymerization reaction is generally carried out at temperatures between 25 ° C and 150 ° C under pressure up to 10 MPa. The preparation of the furanoelastomers object of the present invention, preferably carried out in aqueous emulsion in the presence of an emulsion, dispersion or microemulsion of the perfluoropolyoxyalkylenes according to U.S. Patents 4,769,717 and US 4,664,006, which they are incorporated herein by reference. The following examples are given for illustrative purposes, but not limiting the scope of the present invention.

EXAMPLES 1-7 EXAMPLE 1 A rubber TECN0FL0NR PFR 94 (perf luoro-me i lvini léter PMVE 40 mole%, 60 mole% TFE), which contains 0.4% by weight of iodine which is derived from the introduction of chain transfer agent C? F12I2 and 0.057 mole% of a bis-olefin, B0 which has the formula CH ^ CH (CF a.) CH-LH-j, is used for the preparation of the curable compositions of the present invention. To 100 g of such rubber are mixed: - 1.5 phr of peroxide LUPERC0R 101 XL (2, 5-d? Met? L-2, -di (terbutylperoxy) hexane); -2.13 phr of B0 having the formula CH2 = CH (CFa!) < faCH = CH12; - 5 phr of ZnO; - 15 phr of carbon black MT. The mixing is carried out in an open mixer. The curing curve was determined in the composition, obtained in this way by an Oscillating Disc Rheometer (ORD) by Monsanto (Model 100S), in accordance with ASTM D2064-61, operating at 177 ° C with an oscillation amplitude of 3 °. . The data (ODR) are reported in Table 1: M (moment of minimum torque); MM (maximum torque moment); tß2. (time required for a torque increase of 35.71 kg / cma above Mt_); t '50 and t' 90 time required for an increase of 50% and 90%, respectively, of the torque). On the cured product were determined and reported in Table 1: - established understanding on the ring in the form of 0 to 200 ° C for 70 h after the past-cure at 200 ° C for 6 h (ASTM D395); - the mechanical properties after the post-curing at 200 ° C for 6 h (ASTM D412-63), in particular the heat transfer at 275 ° C for 70 h (ASTM D573).

EXAMPLE 2 (comparative) The example is repeated using 2 phr of TAIC instead of bis-olefin.

EXAMPLE 3 Example 1 is repeated, but using 0.67 phr of TAIC and 1.42 phr of bis-olefin.

EXAMPLE Example 3 is repeated but using 0.2 phr of TAIC and 1.91 phr of bis-olefin.

TABLE 1 From the results of Table 1 it can be seen that the curing system of the invention (bisolef inas) compared with the conventional curing system (TAIC) allows to obtain articles capable of supporting 275 ° C while articles cured with TAIC are products which It has no industrial applicability at these temperatures. Small amounts of TAIC added to the bis-olefin allow products to be obtained, which combine properties of high thermal resistance at 275 ° C with an improvement in established understanding compared to products cured only with bis-olefin.

EXAMPLES 5-6 Example 1 is repeated but using the compositions of Table 2 and as polymer Tecnoflon® PF * + 295 by Ausimont. The thermal resistance was determined at 275 ° C and also at 300 ° C in accordance with ASTM D573 as reported in Table 2. lñ TABLE 2 From the results of Table 2, it can be seen that also at 300 ° C the polymers cured according to the curing system of the present invention, still show a high thermal resistance: especially as shown by the variation data of elongation at breach.

Claims (14)

1. NOVELTY OF THE INVENTION CLAIMS i. The curing system for the curable lumoelastomers by the peroxidic route, which comprises iodine, which comprises as a curing agent a bis-olefin having the general formula characterized in that: Rj., Rβ, R3, R ^, RB, R6 equal or different from each other, are H or Cx-C3 alkyl; Z is a linear or branched alkylene or cycloalkylenic radical of C -C1? which optionally contains oxygen atoms, preferably at least partially fluorinated or a (per) fluoro-polyalkylene radical.
2. 2. The curing system for the curable lumoelastomers by the peroxidic route, which comprises iodine according to claim 1, characterized in that Z is a perfluoroalkylidemal radical of CL, -C12, or a radical (per) f-loropolioxyalkylenic which consists of one or more units selected from the following: -CF ^ CF -J3-, -CFaCF (CFa) 0-, -CFX..0- where X, = F, CFa, -CF- ^ F ^ FaO-, CFa-CFaCHaO-, CaF D-; R t, R a, R 5, R b, R 6 are preferably hydrogen.
3. 3. The curing system for the curable lumoelastomers by the peroxidic route, which comprises vodo according to claim 2, characterized in that Z is a perfluorooxyalkylene having the formula: - (Q) p-CFs.0- (CFaCFaO), "(CF ^ O) ^ -CF ^ - (Q) p- (II) wherein: Q is an alkylene or oxyalkylene radical of Cj.-C10; p is 0 or 1; m and n are such numbers that the ratio m / n is between 0.2 and 5 and the molecular weight of the radical (per) f-lorioxyalkylenic radical is comprised between 500 and 10,000. .
4. The curing system for the curable lumoelastomers by the peroxidic route, which comprises iodine according to claims 1-3, characterized in that the amount of curing agent is comprised between 0.5-10% by weight with respect to the polymer.
5. 5. The curing system for the f luoroelastomers curable by the peroxidic route, which comprises iodine according to claims 1-, characterized in that the content of iodine in the luoroelastomer f is present in the terl position and / or as a comonomer iodized in the polimépca chain.
6. 6. The curing system for the curable luoroelastomers by the peraxidic route, which comprises iodine according to claims 1-5, characterized in that it also contains conventional curing agents.
7. 7. The curing system for the curable lumoelastomers by the peroxidic route, which comprises iodine according to claim 6, characterized in that the conventional curing agent is tpalyl isocyanurate. & .
8. The curing system for the curable urea elastomers by the peroxidic route, which comprises iodine according to claims 1-7, characterized in that the fluoro elastomer is a TFE copolymer and / or vinylidene fluoride having at least one fluorinated olefin having a terl unsaturation, which contains at least one fluorine atom in each carbon atom of the double bond, the other atoms can be fluorine, hydrogen, f-loroalkyl or fluoroalkaxy of 1 to 10 carbon atoms.
9. 9. The curing system for the curable lumoelastomers by the peroxidic route, which comprises iodine according to claim &, characterized in that the luoroelastomer f is a TFE copolymer.
10. 10. The curing system for the curable lumoelastomers by the peroxidic route, which comprises iodine according to claims ñ and 9, characterized in that the luoroelastomer can be selected from: (i) VDF-based copolymers in which The latter is copolymerized with at least one comonomer selected from: perfluoroolefins of a-CA, such as tetraf luoroet i lo (TFE), hexaf luoropropene < HFP); chloro- and / or bromo- and / or iodo-f luoroolef inas of Ca-CA, such as lorotr i f luoroet i leño (CTFE) and bromotr i f luoroet i leño; (per) f luoroalqu i lvín i léteres (PAVE) CFa¡ = CF0R £, in which Rt is a (per) f luoroalqu i lo of C ^, for example tr i f luoromet i lo, bro odif luoromet lio pentaf luoropropilo; perf luro-o? ialqu i lvini léteres in which X is a perf luorooxalt lo of Ct-? J12 having one or more ethereal groups, for example perf luoro-2-propox? -prop? lo; fluorine-free olefins (01) of Ca-CA, for example ethylene and propylene; (n) TFE-based copolymers, which are preferred according to the present invention, in which TFE is co-liquified with at least one camsnomer selected from: (per) f-alkyl alkylvinyl ethers (PAVE) CF-GFORI where R £ is defined as in the above; perf luoro-o? ialqui lvinyl ethers CF ^ CFOX, wherein X is defined as above; f luroroolef inas of Ca-Cß containing hydrogen and / or chlorine and / or bromine and / or iodine atoms; Olefins without fluoro (01) of Ca-C?).
11. 11. The curing system for the curable luoraelastomers by the peroxydic route, which comprises iodine according to claim 10, characterized in that the basic monomeric compositions are selected from the following compositions (% by mole): (a) VDF from 45-65, HFP of 15 -? + 5%, TFE of 0-30%; (b) VDF of 50-60%, PAVE of 5-50%, TFE of 0-20%; (c) VDF of 20-30%, 01 of 10-30%, HFP and / or PAVE of 16-27%, TFE of 10-30%; (d) TFE of 50-60%, P VE of 20-50%; (e) TFE of 45-65%, 01 of 20-55%, VDF of 0-30%; (f) EFE of 32-60%, 01 of 10-40%, PAVE of 20-40% which optionally contains small amounts of a bis-olefin of formula (I): - of 33-75% by moles of tetraf luoroet i leño (TFE), preferably 40-60%; - 15-45% by moles of a perfluorovinyl ether (PVE), preferably 20-40%; - 10-22% by moles of vinylidene fluoride (VDF), preferably 15-20%.
12. 12. The fluoroelastomeric curable by a peroxidic route, characterized in that it comprises how the curing system comprises iodine according to one of the claims 1 to 11.
13. 13. The f luoroelastomers cured by the peroxidic route, which comprises iodine comprising Curing system one of claims 1 to 11.
14. 14. The use of the f luoroelastomers cured by the peroxidic route, which comprises iodine according to claim 13 to obtain seals and seal rings.