Patent Application
20220017736
This application claims priority to European patent application No. 18213892.5 filed on Dec. 19, 2018, the whole content of this application being incorporated herein by reference for all purposes.
The present invention relates to a curable composition and to a blend obtained by dynamic curing of said composition.
Thermoplastic vulcanizates (TPV) are two-phase compositions comprising a thermoplastic material as continuous phase and an elastomeric material as dispersed phase, produced by simultaneous mixing the two materials and cross-linking the elastomeric one while keeping the thermoplastic in the molten state. Typically, the elastomeric material forms cross-linked particles uniformly dispersed in the thermoplastic. Said process is well known as dynamic vulcanization.
These materials are particularly advantageous in that they derive their rubber-like properties from the dispersed phase, so that they can be notably used in all rubber-typical fields of use (sealing articles, including seals and gaskets, pipes, hoses, flat sheets, and the like), while being processable as thermoplastics, including possibility of reforming scraps, flashes or defective parts.
In blends of two or more thermoplastic materials, dynamic vulcanization of one or more thermoplastic materials is also advantageously used to stabilize the disperse phase in order to avoid particles coalescence and phase separation during subsequent processing of the blend and, if the reaction involves more than one component, to promote compatibilization of the different components of the blends.
Dynamic vulcanization allows to prepare materials which are melt processable despite one phase is cross-linked, as the non-crosslinked component remains continuous even at high concentration. This approach is normally applied to prepare TPVs with a high content of elastomeric phase.
Several curing systems are employed to cross-link fluorinated polymers. For instance, peroxide-based cross-linking systems, ionic-based cross-linking systems or nitrile-based cross-linking systems are notably used for curing elastomers. More in particular, the peroxide-based systems generally comprise at least one organic peroxide (e.g. 5-bis(tert-butylperoxy)-2,5-dimethylhexane) and at least one polyunsaturated co-agent (e.g. 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione).
However, the cross-linking systems known in the art for curing fluorinated polymers have issues when used in the dynamic vulcanization in a thermoplastic matrix requiring high processing temperatures, in particular temperatures higher than 300° C. Examples of thermoplastics requiring processing temperatures above 300° C. are notably copolymers of tetrafluoroethylene (TFE) and aromatic polymers like poly(p-phenylene sulphide) (PPS). Actually, organic peroxides contained in said cross-linking systems generally possess decomposition temperatures well below 300° C. As a consequence, organic peroxides decompose at temperatures much lower than the required temperature of processing and a significant amount of radical species required for the cross-linking activation is effectively generated well below said temperature of processing. Accordingly, in the presence of said organic peroxides, significant cross-linking may occur in the heating phase, i.e. well before the thermoplastic polymer is actually melted, thus hindering the effective dynamic vulcanization leading to an optimum dispersion of the dispersed phase in the thermoplastic matrix.
Need is therefore felt to provide for a curable composition based on a high processing temperature thermoplastic, able to deliver a blend having a broad temperature range of application and possessing outstanding mechanical properties even at high temperature.
In a first aspect, the present invention relates to a curable composition comprising:
wherein:
each R, equal to or different from each other, is independently selected from the group consisting of hydrogen; halogen; C1-C20 alkyl, linear or branched, optionally substituted and/or optionally fluorinated; C1-C20 oxyalkyl, linear or branched, optionally substituted and/or optionally fluorinated; (per)fluoropolyether chain; aromatic or heteroaromatic radical, monocyclic or polycyclic, optionally substituted and/or optionally fluorinated; —SiR13, —(R12SiO)bR1, —PR12 wherein each R1, equal to or different from each other, is independently selected from the group consisting of hydrogen, C1-C20 alkyl, linear or branched, optionally substituted and/or optionally fluorinated and wherein b is an integer of at least 1; and
A1 and A2, equal to or different from each other, are each independently selected from the group consisting of hydrogen; halogen; C1-C20 alkyl, linear or branched, optionally substituted and/or optionally fluorinated; C1-C20 oxyalkyl, linear or branched, optionally substituted and/or optionally fluorinated; (per)fluoropolyether chain; —(R12SiO)bR1 wherein R1 and b are as defined; aromatic or heteroaromatic radical, monocyclic or polycyclic, optionally substituted and/or optionally fluorinated; A, and A2 being preferably comprised in an aliphatic or aromatic cyclic structure, optionally substituted and/or optionally fluorinated.
In a second aspect, the present invention relates to a method for manufacturing the above curable composition, said method comprising at least one step of mixing said at least one polymer (E), said at least one agent (C) and said at least one thermoplastic (P).
In a third aspect, the present invention relates to a method for manufacturing a blend comprising a continuous thermoplastic polymer phase and a dispersed vulcanized polymer phase, said method comprising dynamic vulcanization of the curable composition identified above.
Further, the present invention relates to a blend comprising a continuous thermoplastic polymer phase and a dispersed vulcanized polymer phase, the blend being obtained by the above defined method.
In another aspect, the present invention relates to a method for manufacturing a shaped article, said method comprising moulding said blend.
The Applicant has surprisingly found that the curing agents of formula (I) are effective in generating radical species at high temperatures, even above 350° C., and therefore they can be used in dynamic vulcanization at such temperatures, thus allowing the use of high processing temperature thermoplastic polymers. Furthermore, the Applicant has surprisingly found that the curing agents of formula (I) are also suitable to be used within the short residence times of reactive extrusion, which is typically used to carry out the dynamic vulcanization.
In the present description, unless otherwise indicated, the following terms are to be meant as follows.
The term “cure site” is intended to indicate a point susceptible to chemical attack/reaction.
The term “(per)fluoropolymer” is intended to denote a fully or partially fluorinated polymer, comprising recurring units derived from at least one ethylenically unsaturated monomer comprising at least one fluorine atom (hereafter, (per)fluorinated monomer (F)) and, optionally, recurring units derived from at least one ethylenically unsaturated monomer free from fluorine atoms (hereafter, hydrogenated monomer (M)).
The term “(per)fluoroelastomer” is intended to indicate a fully or partially fluorinated elastomer, in particular comprising more than 10% (wt), preferably more than 30% (wt), of recurring units derived from at least one (per)fluorinated monomer (F) and, optionally, recurring units derived from at least one hydrogenated monomer (M).
The term “elastomer” is intended to designate an amorphous product or a product having a low degree of crystallinity (crystalline phase less than 20% by volume), said product possessing a heat of fusion (ΔHf) of less than 10 J/g, preferably less than 5 J/g, more preferably less than 2.5 J/g, and a glass transition temperature (Tg) below 10° C., preferably below 5° C., more preferably below 0° C. Heat of fusion (ΔHf) and glass transition temperature (Tg) are determined according to ASTM D3418.
The term “thermoplastic” is intended to denote a polymer which softens on heating and hardens on cooling at room temperature, which at room temperature exists below its glass transition temperature if fully amorphous or below its melting point if semi-crystalline. It is nevertheless generally preferred for said polymer to be semi-crystalline, which is to say to have a definite melting point; preferred polymers are those possessing a heat of fusion (ΔHf) of at least 10 J/g, preferably of at least 25 J/g, more preferably of at least 30 J/g, when determined according to ASTM D3418. Without upper limit for heat of fusion being critical, it is nevertheless understood that said polymer will generally possess a heat of fusion of at most 80 J/g, preferably of at most 60 J/g, more preferably of at most 40 J/g.
In the present description, the use of parentheses “( . . . )” before and after the names of compounds, symbols or numbers identifying formulae or parts of formulae like, for example, “polymer (E)” and “thermoplastic (P)”, has the mere purpose of better distinguishing those names, symbols or numbers from the remaining text; thus, said parentheses could also be omitted.
Curing Agent (C)
As said, the curable composition according to the invention comprises at least one curing agent of formula (I) above.
The ethynyl groups on adjacent carbon atoms in formula (I) are known to dimerize upon application of heat to form an aromatic ring having a 1,4-diradical. While not being bound by theory, it is believed that the 1,4-diradical may promote the cross-linking or curing process via a Bergman cyclization reaction such as the one disclosed by Warner et al. in Science, 268, (1995), pp. 814-816.
The nature of each R group in formula (I) is not particularly critical to the invention; however, the size of the R groups may, due to steric hindrance, undesirably interfere with the dimerization reaction of the ethynyl groups. In general, any R group which does not prevent the formation of a 1,4-diradical from the reaction of the ethynyl groups upon thermal treatment can be used in the compounds of formula (I).
Each R group is preferably selected among: hydrogen; halogen; C1-C8 alkyl, linear or branched, optionally substituted and/or optionally fluorinated (e.g. —CH3, —C(CH3)3, —CF3, —C2F5, —C3F7); C1-C3 oxyalkyl, linear or branched, optionally substituted and/or optionally fluorinated (e.g. —OCH3, —OCF3); (per)fluoropolyether chain; —(R12SiO)bR1 wherein b and R1 are as defined above; aromatic or heteroaromatic radical, monocyclic or polycyclic, optionally substituted and/or optionally fluorinated.
When aromatic, each R group preferably has from 6 to 15 carbon atoms, more preferably from 6 to 10 carbon atoms. When aromatic, R is preferably an unsubstituted or substituted phenyl group, e.g. a phenyl substituted with one or more fluorine atoms or with a C1-C6 alkyl or oxyalkyl group optionally fluorinated, e.g. —CH3, —CF3, —OCH3, —OCF3. Even more preferably, when aromatic, R is an unsubstituted phenyl group.
Each R group may be a (per)fluoropolyether chain. Suitable (per)fluoropolyether chains may be represented by formula —RF—OZ-T wherein: T is selected from a fluorine atom, a chlorine atom and a C1-C3 (per)fluoroalkyl group comprising, optionally, one or more hydrogen or chlorine atoms; z is equal to 0 or 1; and RF is a divalent (per)fluoropolyether radical selected from the following:
Typically p, q, r, s, t, u, v, w and x in the formulas above are selected so that the number average molecular weight of the (per)fluoropolyether radical RF is between 500 and 10,000, preferably between 800 and 5000.
Preferably, A1 and A2 are part of an optionally substituted aliphatic or aromatic cyclic structure having from 5 to 10 carbon atoms, such as:
When A1 and A2 are part of an aliphatic or aromatic cyclic structure, said structure may be substituted on any of the carbon atoms.
A1 and A2 are preferably part of an aromatic cyclic structure, more preferably of an aromatic cyclic structure having from 6 to 10 carbon atoms, even more preferably of an unsubstituted or substituted phenyl ring.
Representative examples of compounds of formula (I) include but are not limited to:
Preferably, A1 and A2 comprise a 1,5 enediyne moiety.
According to a preferred embodiment, said curing agent has formula (II) herein below:
wherein:
each R, equal to or different from each other, is as defined above;
X is a divalent bridging group selected from a carbon-carbon bond; a C1-C20alkylene radical, optionally substituted (e.g. —C(CH3)2—) and/or optionally fluorinated (e.g. —(CF2)n—, —C(CF3)2—); a divalent (per)fluoropolyether radical RF as defined above; an organopolysiloxane radical —(R12SiO)b— wherein R1 and b are as defined above; a —O— radical; a —S— radical; a —SO2— radical; a —C(O)— radical; a fused aromatic or heteroaromatic structure optionally substituted and/or optionally fluorinated.
More preferably X is selected from a C1-C20 fluorinated alkylene radical, optionally substituted, or a divalent (per)fluoropolyether radical RF as above defined. Suitable C1-C20 fluorinated alkylene radicals are for instance —C(CF3)2— or those of formula —(CF2)n— wherein n is an integer from 1 to 20, e.g. 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, 20.
Representative examples of compounds of formula (II) include but are not limited to:
Compounds of formula (I) or (II) can be prepared according to known processes such as those described in Smith, D. W., Babb, D. A.; J. Am Chem. Soc. 120, n. 35, (1998) 9078-9079 or in Basak, A., Mandal, S., Bag, S. S.; Chemical Rev. 103, (2003) 4077-4094.
Polymer Comprising Cure Sites [Polymer (E)]
Polymer (E) may be any polymer which is suitable to be cross-linked, preferably suitable to be cross-linked with a radical initiated mechanism. Typically, polymers that may be cross-linked by a radical route comprise cure sites in their backbone, either provided by suitable functional groups present in recurring units from functional monomers incorporated in the polymer chain or provided by reactive end-groups, e.g. formed by suitable chain transfer agents (e.g. halogen-containing cure-sites). The term “backbone” is intended to indicate the longest series of covalently bonded atoms that together create a continuous chain.
Preferably, said polymer (E) comprises at least one of chlorine, iodine and bromine cure site in an amount such that its content ranges between 0.001 and 10% (wt), with respect to the total weight of the polymer (E). Iodine and bromine cure sites are preferred because they maximize the curing rate. For ensuring acceptable reactivity, the content of iodine and/or bromine in the polymer (E) should be of at least 0.05% (wt), preferably of at least 0.1% (wt), more preferably of at least 0.15% (wt), with respect to the total weight of the polymer (E). On the other side, amounts of iodine and/or bromine preferably not exceeding 7% (wt), more specifically not exceeding 5% (wt), or even not exceeding 4% (wt), with respect to the total weight of the polymer (E), are generally selected for avoiding side reactions and/or detrimental effects on thermal stability.
According to an embodiment, said iodine and/or bromine cure sites are comprised as pending groups bound to the backbone of the polymer chain.
The introduction of these iodine and/or bromine cure sites may be performed by adding, during manufacture of the polymer (E), brominated and/or iodinated comonomers, otherwise called brominated and/or iodinated cure-site comonomers. Non limitative examples of said brominated and/or iodinated cure-site comonomers are notably:
As an alternative to or in combination with above mentioned iodine and/or bromine cure sites, said polymer (E) may comprise iodine and/or bromine atoms as terminal groups of the backbone of the polymer chain. These iodine and/or bromine atoms are typically introduced during manufacture of polymer (E), by polymerizing in the presence of iodinated and/or brominated chain-transfer agents. Among said chain-transfer agents mention can be made of: (i) alkali metal or alkaline-earth metal iodides and/or bromides, and (ii) iodine and/or bromine containing fluorocarbon compounds. In this view, preferred iodinated and/or brominated chain-transfer agents are those of formula Rf(I)x(Br)y, where Rf is a (per)fluoroalkyl or a (per)fluorochloroalkyl containing from 1 to 8 carbon atoms, while x and y are integers between 0 and 2, with 1≤x+y≤2. The use of these compounds is for instance described in U.S. Pat. No. 4,243,770 (DAIKIN IND LTD) 6 Jan. 1981 and U.S. Pat. No. 4,943,622 (NIPPON MEKTRON KK [JP]) 24 Jul. 1990.
Suitable polymers (E) may be hydrocarbon polymers or (per)fluoropolymers.
Notable examples of hydrocarbon polymers are for instance ethylene copolymers, ethylene/propylene/diene copolymers (e.g EPDM), styrene-butadiene copolymers, poly(butylene), chlorinated rubber, chlorinated ethylene polymers and copolymers, aromatic polymers comprising sulfone or sulfide bridging groups such as polyphenylenesulfide, polysulfone, polyethersulfone, polyphenylsulfone.
Preferably, polymer (E) is a (per)fluoropolymer. As said, a (per)fluoropolymer comprises recurring units derived from at least one (per)fluorinated monomer (F).
Preferably, said (per)fluorinated monomer (F) is selected from the group consisting of:
wherein each of Rf3, Rf4, Rf5, Rf6, equal to or different from each other, is independently a fluorine atom, a C1-C6 fluoro- or per(halo)fluoroalkyl, optionally comprising one or more than one oxygen atom, such as notably e.g. —CF3, —C2F5, —C3F7, —OCF3, —OCF2CF2OCF3.
In addition to (per)fluorinated monomers (F), polymer (E) may also comprise hydrogenated monomers (M), such as ethylene and propylene.
In a first embodiment, said at least one polymer (E) is a (per)fluoroelastomer. For the sake of brevity, said (per)fluoroelastomer will be also referred to as elastomer (E1).
As said, in addition to recurring units derived from at least one (per)fluorinated monomer (F) selected from the group identified above, the elastomer (E1) may also comprise recurring units derived from at least one hydrogenated monomer (M). Examples of hydrogenated monomers (M) are notably hydrogenated alpha-olefins, including ethylene, propylene, 1-butene, diene monomers, styrene monomers, alpha-olefins being typically used.
Preferably, the elastomer (E1) is selected among:
(1) VDF-based copolymers, in which VDF is copolymerized with at least one additional comonomer selected from the group consisting of:
(a) C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP);
(b) hydrogen-containing C2-C8 olefins, such as vinyl fluoride (VF), trifluoroethylene (TrFE), hexafluoroisobutene (HFIB), perfluoroalkyl ethylenes of formula CH2═CH—Rf, wherein Rf is a C1-C6 perfluoroalkyl group;
(c) C2-C8 fluoroolefins comprising at least one of iodine, chlorine and bromine, such as chlorotrifluoroethylene (CTFE);
(d) (per)fluoroalkylvinylethers (PAVE) of formula CF2═CFORf, wherein Rf is a C1-C6 (per)fluoroalkyl group, preferably CF3, C2F5, C3F7;
(e) (per)fluoro-oxy-alkylvinylethers of formula CF2═CFOX, wherein X is a C1-C12 ((per)fluoro)-oxyalkyl comprising catenary oxygen atoms, e.g. the perfluoro-2-propoxypropyl group;
(f) (per)fluorodioxoles having formula (III) above;
(g) (per)fluoro-methoxy-vinylethers (MOVE, hereinafter) having formula: CF2═CFOCF2ORf2
wherein Rf2 is selected from the group consisting of C1-C6 (per)fluoroalkyls; C5-C6 cyclic (per)fluoroalkyls; and C2-C6 (per)fluorooxyalkyls, comprising at least one catenary oxygen atom; Rf2 is preferably —CF2CF3 (MOVE1); —CF2CF2OCF3 (MOVE2); or —CF3 (MOVE3);
(h) C2-C8 non-fluorinated olefins (OI), for example ethylene and propylene; and
(2) TFE-based copolymers, in which TFE is copolymerized with at least one additional comonomer selected from the group consisting of the classes (c), (d), (e), (g), (h) as above detailed, and class (i) below, with the provision that such comonomer is different from TFE:
(i) perfluorovinylethers containing cyanide groups, such as notably those described in patents U.S. Pat. Nos. 4,281,092, 5,447,993 and 5,789,489.
More preferably, the elastomer (E1) is a perfluoroelastomer. The term “perfluoroelastomer” is intended to denote an elastomer substantially free of hydrogen atoms. The expression “substantially free of hydrogen atoms” is understood to mean that the perfluoroelastomer consists essentially of recurring units derived from ethylenically unsaturated monomers comprising at least one fluorine atom and free of hydrogen atoms [per(halo)fluoromonomer (PFM)].
Minor amounts of moieties derived from hydrogen-containing recurring units might be present provided that they do not substantially affect the properties of the perfluoroelastomer. An amount not exceeding 1% moles (preferably not exceeding 0.5% moles) with respect to total moles of per(halo)fluoromonomers (PFM) is generally considered as fulfilling the “perfluoroelastomer” behaviour.
Even more preferably, the elastomer (E1) comprises recurring units derived from TFE and a perfluoroalkylvinylether, said perfluoroalkylvinylether being preferably perfluoromethylvinylether (MVE).
The amount of recurring units derived from said perfluoroalkylvinylether is preferably of at least 25% (mol), more preferably of at least 30% (mol), with respect to total moles of TFE and perfluoroalkylvinylether.
The amount of recurring units derived from said perfluoroalkylvinylether is preferably of at most 40% (mol), more preferably of at most 35% (mol), with respect to total moles of TFE and perfluoroalkylvinylether.
The amount of recurring units derived from TFE is preferably of at least 60% (mol), more preferably of at least 65% (mol), with respect to total moles of TFE and perfluoroalkylvinylether.
The amount of recurring units derived from TFE is preferably of at most 80% (mol), more preferably of at most 70% (mol), with respect to total moles of TFE and perfluoroalkylvinylether.
Said elastomer (E1) may comprise, in addition to recurring units derived from TFE and said perfluoroalkylvinylether, recurring units derived from at least another per(halo)fluoromonomer (PFM).
Should said elastomer (E1) comprise recurring units derived from at least one per(halo)fluoromonomer (PFM) different from TFE and said perfluorovinylether, these recurring units are preferably comprised in an amount not exceeding 5% (mol), more preferably not exceeding 3% (mol), with respect to total moles of recurring units derived from TFE and perfluorovinylether.
Non limitative examples of suitable per(halo)fluoromonomers (PFM) are notably:
Optionally, said elastomer (E1) also comprises recurring units derived from a bis-olefin of general formula (IV) here below:
wherein:
The amount of recurring units derived from said bis-olefins is generally between 0.01 and 1.0% (mol), preferably between 0.03 and 0.5% (mol), more preferably between 0.05 and 0.2% (mol) with respect to the total moles of recurring units derived from TFE and MVE.
As said, the elastomer (E1) further comprises cure sites.
Preferred elastomers (E1) are those consisting essentially of:
Elastomers (E1) suitable for the purpose of the invention can be prepared by any known method, such as emulsion or micro-emulsion polymerization, suspension or micro-suspension polymerization, bulk polymerization and solution polymerization.
In a second embodiment, said at least one polymer (E) is a thermoplastic (per)fluoropolymer. For the sake of clarity, said thermoplastic will be also referred to below as thermoplastic (E2).
As said, in addition to recurring units derived from at least one (per)fluorinated monomer (F) selected from the group identified above, the thermoplastic (E2) may additionally comprise recurring units derived from at least one hydrogenated monomer (M), which is preferably selected from:
In a preferred embodiment, said thermoplastic (E2) consists essentially of recurring units derived from TFE and at least one (per)fluoroalkylvinylethers of formula CF2═CFORf1. Preferably, said (per)fluoroalkylvinylether is perfluoropropylvinylether (PPVE), with Rf1 being a propyl.
The amount of recurring units derived from TFE preferably ranges from 80 to 99% (mol), more preferably from 90 to 99% (mol), even more preferably from 95 to 98% (mol), with respect to total moles of TFE and (per)fluoroalkylvinylether.
The amount of recurring units derived from said (per)fluoroalkylvinylether preferably ranges from 1 to 20% (mol), more preferably from 1 to 10% (mol), even more preferably from 2 to 5% (mol), with respect to total moles of TFE and (per)fluoroalkylvinylether.
In another embodiment, said thermoplastic (E2) consists essentially of recurring units derived from TFE.
As said, the thermoplastic (E2) further comprises cure sites, preferably iodine cure sites, preferably as terminal groups of the backbone of the polymer chain.
Thermoplastic Polymer [Thermoplastic (P)]
Thermoplastic (P) differs from thermoplastic (E2), particularly in that thermoplastic (P) does not contain cure sites.
Thermoplastic (P) is preferably semi-crystalline.
Said semi-crystalline polymer has a melting point preferably higher than 200° C., more preferably higher than 260° C., even more preferably higher than 280° C., most preferably higher than 300° C., and even higher than 330° C.
According to a first embodiment of the invention, said thermoplastic (P) is fluorinated, that is to say it comprises recurring units derived from at least one (per)fluorinated monomer (F) selected from the group identified above. Said thermoplastic (P) may additionally comprise recurring units derived from at least one hydrogenated monomer (M).
In a preferred embodiment, said thermoplastic (P) consists essentially of recurring units derived from TFE and at least one (per)fluoroalkylvinylethers of formula CF2═CFORf1. Preferably, said (per)fluoroalkylvinylether is perfluoromethylvinylether (MVE), wherein Rf1 is CF3.
The amount of recurring units derived from TFE preferably ranges from 80 to 99% (mol), more preferably from 90 to 99, even more preferably from 95 to 98%, with respect to total moles of TFE and (per)fluoroalkylvinylether.
The amount of recurring units derived from said (per)fluoroalkylvinylether preferably ranges from 1 to 20% (mol), more preferably from 1 to 10% (mol), even more preferably from 2 to 5% (mol), with respect to total moles of TFE and (per)fluoroalkylvinylether.
Thermoplastic (P) consisting of recurring units derived from TFE and the (per)fluoroalkylvinylether possesses a melting point exceeding 200° C., preferably exceeding 260° C., more preferably exceeding 270° C., even more preferably exceeding 280° C. The melting temperature is determined by Differential Scanning Calorimetry (DSC) at a heating rate of 10° C./min, according to ASTM D 3418.
In another embodiment, said thermoplastic (P) consists essentially of recurring units derived from TFE.
According to a second embodiment of the invention, said thermoplastic (P) is non-fluorinated, that is to say it comprises recurring units derived from fluorine-free monomer(s).
Preferably, said thermoplastic (P) is an aromatic polymer.
According to a preferred embodiment, said aromatic polymer is a poly(arylene sulphide) (PAS). A PAS comprises recurring units (RPAS) of formula —(Ar—S)— as the main structural units, preferably in an amount of at least 80% (mol), wherein Ar is an aromatic group. Examples of Ar include groups of formulas (V-A) to (V-K) given below:
wherein R1 and R2, equal or different from each other, are independently selected among hydrogen atoms, alkyl of 1 to 12 carbon atoms, alkoxy of 1 to 12 carbon atoms, arylene of 6 to 24 carbon atoms, and halogens.
PAS preferably comprises recurring units (RPAS) in which Ar is a group of formula (V-A), more preferably in which R1 and R2 are hydrogen atoms. Accordingly, PAS is preferably a poly(phenylene sulphide) (PPS), which is notably available as RYTON® PPS from Solvay Specialty Polymers USA, L.L.C.
According to another embodiment, said aromatic polymer is an aromatic sulfone polymer (SP). For the purposes of the present invention, the definition “aromatic sulfone polymer (SP)” is intended to denote any polymer of which more than 50% (wt), preferably more than 70% (wt), more preferably more than 90% (wt), of recurring units (RSP) comprise at least one group of formula (VI):
wherein Ar′ is a group chosen among the following structures:
with RD being selected among:
with n being an integer from 1 to 6.
The recurring units (RSP) are preferably chosen from:
Accordingly, the aromatic sulfone polymer (SP) is preferably chosen among the group consisting of: polysulfone (PSU), polyphenylsulfone (PPSU), polyethersulfone (PESU), copolymers and mixtures thereof, and is most preferably a polysulfone (PSU) or polyphenylsulfone (PPSU).
Polysulfone (PSU) is notably available as UDEL® PSU from Solvay Specialty Polymers USA, L.L.C and is made by condensing bisphenol A and 4,4′-dichlorodiphenyl sulfone.
Polyphenylsulfone (PPSU) is notably available as RADEL® R from SOLVAY ADVANCED POLYMERS, L.L.C and is made by reacting units of 4,4′-dichlorodiphenyl sulfone and 4,4′-biphenol.
According to another preferred embodiment, said aromatic polymer is a poly(ether ether ketone) (PEEK). The definition “poly(ether ether ketone) (PEEK)” is intended to denote any polymer of which at least 50% (mol) of recurring units (RPEEK) are recurring units of formula (VII):
based on the total number of moles of recurring units in the PEEK, wherein:
each R1, equal or different from each other, is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium; and
each a, equal to or different from each other, is independently selected from 0, 1, 2, 3, and 4. Preferably, each a is 0.
Preferably at least 60% (mol), at least 70% (mol), at least 80% (mol), at least 90% (mol), at least 95% (mol), or at least 99% (mol) of the recurring units (RPEEK) are recurring units of formula (VII).
Preferably, the phenylene moieties in recurring units (RPEEK) have 1,3- or 1,4-linkages.
In some embodiments, more than 50% (mol) of recurring units (RPEEK) are recurring units of formula (VII-A):
where each R2 and b, at each instance, is independently selected from the groups described above for R1 and a, respectively. b in formulae (A-1) is an integer ranging from 0 to 4, preferably 0.
Preferably at least 60% (mol), at least 70% (mol), at least 80% (mol), at least 90% (mol), at least 95% (mol) or at least 99% (mol) of recurring units (RPEEK) are recurring units of formula (VII-A). Said PEEKs are notably available as KetaSpire® KT-820 or KetaSpire® KT-880 from Solvay Specialty Polymers USA, L.L.C.
Curable Composition
The curable composition of the invention comprises said at least one agent (C) in an amount preferably of at least 0.1% (wt), more preferably of at least 1% (wt), and preferably of at most 10% (wt), more preferably of at most 4% (wt), with respect to the total weight of the composition.
Said composition comprises said at least one polymer (E), being it the elastomer (E1) or the thermoplastic (E2), in an amount preferably of at least 10% (wt), more preferably of at least 25% (wt), even more preferably of at least 35% (wt), and preferably of at most 90% (wt), more preferably of at most 75%, even more preferably of at most 45% (wt), with respect to the total weight of the composition.
According to various embodiments of the invention, said composition comprises at least one elastomer (E1), or at least one thermoplastic (E2), or a combination thereof.
Said composition comprises said at least one thermoplastic (P) in an amount preferably of at least 10% (wt), more preferably of at least 60% (wt), and preferably of at most 90% (wt), more preferably of at most 70% (wt), with respect to the total weight of the composition.
According to a preferred embodiment, said composition comprises at least one metal oxide or hydroxide, more preferably MgO. Said at least one metal oxide or hydroxide advantageously promotes the cross-linking of the polymer (E).
Accordingly, said composition comprises said at least one metal oxide or hydroxide in an amount preferably of at least 0.1% (wt), more preferably of at least 1% (wt), and preferably of at most 10% (wt), more preferably of at most 4% (wt), with respect to the total weight of the composition.
Blend
As said, the present invention also relates to a method for manufacturing a blend comprising a continuous thermoplastic polymer phase and a dispersed vulcanized polymer phase, said method comprising dynamic curing of the curable composition identified above.
The dynamic curing procedure is well known to a person skilled in the art and includes heating the composition in an extruder or a mixer at a temperature at which both the thermoplastic (P) and the polymer (E) are in their molten state, that is above their respective glass transition or melting temperatures whatever is the highest, and vulcanizing the polymer (E) while exerting a mixing shearing force. According to the method of the present application, said temperature is preferably at least 300° C., more preferably at least 320° C., even more preferably at least 350° C.
Dynamic vulcanization can be performed using standard mixing devices, preferably using extruder devices, with twin-screw extruders being preferred. An example of dynamic curing procedure is disclosed in WO2015/014698 (Solvay Specialty Polymers Italy S.P.A.) 5 May 2015.
According to the method of the invention, ingredients of the composition can be pre-mixed all together and fed to the extruder e.g. through a single hopper, or can be fed to the extruder through separated feeders. It is generally preferred to add a masterbatch comprising the polymer (E), the agent (C) and, if present, the metal oxide or hydroxide, through a separate feeder, which will deliver said masterbatch in the molten mass of the thermoplastic (P).
As a result of the dynamic curing procedure, said polymer (E) is at least partially chemically cross-linked. If referred to a (per)fluoroelastomer, the expression “partially chemically cross-linked” is intended to denote that the polymer (E) is cross-linked to such an extent that it retains elastomeric properties.
Said blend is commonly termed thermoplastic vulcanizate (TPV) if the dispersed phase is elastomeric.
As said, the present invention also relates to a method for manufacturing a shaped article, said method comprising moulding said blend. The technique used for moulding is not particularly limited; standard techniques including shaping the blend in a molten/softened form can be advantageously applied, and include notably compression moulding, extrusion moulding, injection moulding, transfer moulding and the like.
The blend according to the present invention has several advantages, for example: good mechanical properties, notably in terms of ductility and flexibility, a broad temperature range of application, and notable thermal-chemical resistance. Therefore, said blend can be suitably used in various fields including automotive, oil and gas, electric and electronics. Particularly, said blend can be advantageously used for manufacturing films, sheets and wire coatings having excellent mechanical and electrical performances, and for injection moulding or extrusion of flexible parts retaining outstanding chemical resistance.
Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.
The invention will now be described with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.
Materials
Curing agent of formula (II-1), hereinafter referred to as BODA, was prepared following the general procedure described in Smith, D. W., Babb, D. A.; J. Am. Chem. Soc. 120, n. 35, (1998) 9078-9079.
TECNOFLON® FFKM PFR94 is a TFE/MVE perfluoroelastomer containing iodine, commercially available from Solvay Specialty Polymers Italy.
HYFLON® MFA 640 is a TFE/MVE thermoplastic polymer with a melting point of 285° C., commercially available from Solvay Specialty Polymers Italy.
RYTON® QA200N is a medium-high viscosity PPS with a melting point of 285° C. and is commercially available from Solvay Specialty Polymers USA.
KetaSpire® KT-880 is a low viscosity PEEK with a melting point of 340° C. and is commercially available from Solvay Specialty Polymers USA.
MgO is commercially available as Maglite-DE® from Hallstar.
Luperox 101 XL 45 is commercially available from Arkema.
Drimix 75% TAIC is commercially available from Finco s.r.l.
Methods
Tensile Measurements
Tensile measurements were performed according to ASTM D638 with the specimen V at 23° C. and with a deformation speed of 10 mm/min.
SEM Analyses
SEM images were obtained by Cambridge SEM 200 scanning electron microscope. The images refer to the surfaces obtained by cryo-fracturing 1 mm thick films from compression moulding.
Photographic Analyses
The photographic analyses were performed on 1 mm thick films from compression molding using the photocamera of a Samsung J6 mobile phone.
Synthesis of Masterbatch A
FFKM PFR 94 (100 g) was mixed with BODA (3 g) and MgO (3 g) at ambient temperature in a Brabender 50 EHT internal mixer using Banbury blades at 10 rpm for 30 minutes. The mixer was cooled with compressed air. The thus obtained masterbatch A was removed from the mixer and finely cut for the synthesis of TPVs according to the examples 1, 2 and 3 (E1 to E3).
MFA 640 (19.5 g) was poured into a Brabender 50 EHT internal mixer using Roller blades and melted for 10 minutes at 30 rpm. Then, the masterbatch A (45.5 g) was added and mixed at 30 rpm for 20 min. A TPV was obtained. The so obtained TPV was manually removed from the mixer, finely cut and subsequently compression molded in a 1 mm thick film to obtain a sample for tensile measurements, photographic analysis and SEM analysis.
Ryton® QA200N (19.5 g) was poured into a Brabender 50 EHT internal mixer using Roller blades and melted for 10 minutes at 30 rpm. Then, the masterbatch A (45.5 g) was added and mixed at 30 rpm for 20 min. A TPV was obtained. The so obtained TPV was manually removed from the mixer, finely cut and subsequently compression molded in a 1 mm thick film to obtain a sample for tensile measurements, photographic analysis and SEM analysis.
KetaSpire® KT-880 (16.5 g) was poured into a Brabender 50 EHT internal mixer using Roller blades and melted for 10 minutes at 30 rpm. Then, the masterbatch A (38.5 g) was added and mixed at 70 rpm for 10 min. A TPV was obtained. The so obtained TPV was manually removed from the mixer, finely cut and subsequently compression molded in a 1 mm thick film to obtain a sample for tensile measurements, photographic analysis and SEM analysis.
Synthesis of Masterbatch B
FFKM PFR 94 (100 g) was mixed with Luperox 101 XL45 (3 g), Drimix 75% TAIC (4 g) and MgO (3 g) at ambient temperature in a Brabender 50 EHT internal mixer using Banbury blades at 10 rpm for 30 minutes. The mixer was cooled with compressed air. The thus obtained masterbatch B was removed from the mixer and finely cut for the synthesis of TPV according to comparative example 4 (CE 4).
Comparative Example 4 (CE 4): Preparation of a Blend Comprising MFA and the Masterbatch B
MFA 640 (19.5 g) was poured into a Brabender 50 EHT internal mixer using Roller blades and melted for 10 minutes at 30 rpm. Then, the masterbatch B (45.5 g) was added and mixed at 30 rpm for 20 min. The so obtained mixture was manually removed from the mixer, finely cut and subsequently compression molded in a 1 mm thick film to obtain a sample for tensile measurements, photographic analysis and SEM analysis.
Properties of Blends According to the Invention
Table 1 reports the mechanical properties of the TPV samples according to examples 1, 2 and 3 (E1, E2 and E3), namely the strain at break, the yield strength, the stress at break, the tensile modulus and the storage modulus at 200° C. Table 1 also reports the strain at break, the yield strength, the stress at break and the tensile modulus of the sample according to the comparative example 4 (CE4)
By a comparison of the mechanical properties of the samples according to E1 and CE4—both comprising MFA 640 as the thermoplastic polymer—it is interestingly noted that the sample according to E1 exhibits significantly greater flexibility and ductility (i.e. greater strain at break), while showing slightly lower strength and stiffness (i.e. lower yield strength and stress at break). It is, therefore, interestingly noted that the sample according to E1 shows a good balance between strength, stiffness, flexibility and ductility.
The sample according to E1 also ensures a significantly better dispersion of the dispersed phase (PFR 94) in the thermoplastic matrix (MFA 640) than the sample according to CE4, as evident from
More in detail, referring to the images from the photographic analysis of
The SEM micrographs of the samples according to E1 and CE4, reported in
| Number | Date | Country | Kind |
|---|---|---|---|
| 18213892.5 | Dec 2018 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/085434 | 12/16/2019 | WO | 00 |
