Patent Application
20250206946
The invention relates to flame-retardant thermoplastic compositions based on polycarbonate having high comparative tracking index.
On account of its high impact strength, high heat distortion resistance and a certain inherent flame retardancy, polycarbonate offers many advantages over other thermoplastic polymers. Due to this unique profile of properties, polycarbonate compositions are suitable for a variety of different applications, for example in the field of electrical and electronic components. In particular, good insulation properties and high flame retardancy are essential safety-relevant basic requirements for materials used in this area. In applications in which the plastic is in direct contact with the electrical conductor paths, a high resistance to tracking currents under voltage load is a prerequisite, in order for there not to be any short circuits within the component and hence a fire.
The comparative tracking index (CTI) describes in general the resistance of a plastics material to environmental influences. The CTI value is a measure of the inclination of a plastic, under environmental influences, such as moisture and soiling, to form under voltage electrically conductive paths on the surface and promote resulting electrical tracking currents. The higher the tracking current resistance or the comparative tracking index (CTI value) of a material, the better suited it is for use in high-voltage applications, for example in modern-day electromobility applications. Another advantage of materials having a high CTI value is the possibility of placing electrical conductor paths in an electronic component closer together without risking a short circuit, which in turn enables the reduction of component dimensions and thus more compact designs and weight savings.
In contrast to other thermoplastic polymers such as polystyrene, polyester, etc., polycarbonate itself has a very low comparative tracking index with moderate flame retardancy. Due to the high proportion of aromatic structures, polycarbonate has a rather high tendency to carbonize. The CTI of pure polycarbonate is about 250 V or even lower (F. Acquasanta et al., Polymer Degradation and Stability, 96 (2011), 2098-2103). However, for numerous applications in the electronics/electricals (EE) sector, for example in the electromobility sector, safety grounds require a high CTI, typically of 600 V (corresponding to insulating material group PLC 0 according to EN 50124), of the materials used. At the same time, the materials must have a high flame retardancy, i.e. a V0 classification according to UL 94V, especially even at thin wall thicknesses.
Although pure polycarbonate typically already has a certain intrinsic flame retardancy (V2 classification according to UL 94 V), this is not sufficient for most applications in the EE sector. In order to achieve the required V0 classification according to UL94V, the addition of suitable flame retardants is required. Typically employed for polycarbonate are halogenated sulfonates (e.g. Rimar salt (potassium perfluorobutanesulfonate, C4 salt) or KSS salt (potassium diphenylsulfone 3-sulfonate)) or also organic phosphates (e.g. bisphenol A bis(diphenyl phosphate) (BDP), resorcinol bis(diphenyl phosphate) (RDP)) or phosphazenes. The mechanism of action of these flame retardants is based on the formation of a solid, carbonized surface layer that interrupts the oxygen supply and thus inhibits the combustion process.
The effect forming the basis for good comparative tracking index is, inter alia, a low tendency to form conductive paths on the surface. This is in direct contrast to the mechanism of action, the “charring”, of surface-active flame retardants and thus poses a particular challenge in the reconciling of CTI and flame retardancy.
The object was therefore that of providing polycarbonate-based compositions that achieve a UL94 V0 classification at 2 mm, particularly preferably at 1.5 mm (after conditioning for 7 days at 20% relative humidity and 70° C. ambient temperature), and also have a high CTI of at least 375 V, preferably at least 400 V, very particularly preferably of 600 V or more, preferably determined according to the rapid test method based on IEC 60112:2009. Due to the area of application and the heat development in EE components, the compositions should preferably also have a good heat distortion resistance, in particular a Vicat softening temperature, determined according to ISO 306:2014-3, VST Method B, of at least 105° C., particularly preferably of at least 110° C.±2° C. Furthermore, the CTI should preferably be robust, i.e. the high CTI should be reliably attained at different operating voltages, not just for instance at 600 V, but also at 300 V or 350 V.
Surprisingly, it has been found that this profile of properties is achieved by specific combinations of aromatic polycarbonate with polyalkyl(meth)acrylate in combination with phosphorus-containing flame retardant and with fluorine-containing anti-drip agent.
The invention thus provides a thermoplastic composition, consisting of
It will be appreciated that all of the components present in the composition according to the invention sum to 100% by weight. Where a numerical range has its upper limit indicated by “to X”, this includes the numerical value specified and its upward rounding range.
It will be appreciated that the components used may contain typical impurities arising for example from their production processes. It is preferable to use the purest possible components. It will further be appreciated that these impurities may also be present in the event of an exhaustive formulation of the composition.
The invention also provides moldings, produced from the thermoplastic compositions according to the invention, i.e. moldings consisting of a thermoplastic composition according to the invention or comprising a region made from a thermoplastic composition according to the invention. Such moldings are in particular those in which the aforementioned profile of properties is particularly attractive, i.e. moldings which are parts of components from the EE sector, in particular of high-voltage switches, inverters, relays, electronic connectors, electrical connectors, circuit breakers, components for photovoltaic applications, electric motors, heat sinks, chargers and charging plugs for electric vehicles, electrical junction boxes, smart meter housings, miniature circuit breakers, busbars. The component is preferably designed for an operating voltage of at least 400 V. To this end, the material advantageously used preferably has a comparative tracking index of at least 600 V, determined as described above according to the rapid test method based on IEC 60112:2009.
The compositions according to the invention exhibit no significant tracking current (>0.5 A over 2 s) when at least 50 drops of a 0.1% ammonium chloride solution are applied at 375 V, further preferably at 400 V, particularly preferably at 600 V, with the test preferably being carried out according to the rapid test method based on IEC 60112:2009 and described in the description part. At the same time, the compositions according to the invention have a flame retardancy V0 according to UL 94 V at thicknesses of the test specimens of 2 mm, further preferably still also of at least V1, particularly preferably of V0, at 1.5 mm, in each case after conditioning the test specimens for 7 days at 20% relative humidity and 70° C. ambient temperature. In addition to the high CTI and the good flame retardancy, the compositions preferably also have a good heat distortion resistance, which is manifested in a Vicat softening temperature, determined according to ISO 306:2014-3, VST Method B, of at least 105° C., further preferably at least 110° C.±2° C.
The invention therefore also provides for the use of 4% by weight to 25% by weight, preferably of 5% by weight to 20% by weight, of polyalkyl(meth)acrylate, 1.5% by weight to 10% by weight, preferably 2% by weight to 8% by weight, of phosphorus-containing flame retardant and 0.3% to 2% by weight of fluorine-containing anti-drip agent, wherein the % by weight figures are based on the resulting overall composition, for attaining a high CTI of 375 V, further preferably 400 V, particularly preferably 600 V, and a UL94 V0 classification at a test specimen thickness of 2 mm, further preferably also of at least V1, particularly preferably V0, at 1.5 mm, especially after conditioning the test specimens for 7 days at 20% relative humidity and 70° C. ambient temperature, in a thermoplastic composition containing at least 70% by weight of aromatic polycarbonate.
Of course, the features mentioned as preferred, particularly preferred, and so on, for the composition also apply with regard to the use according to the invention.
The individual constituents of the compositions according to the invention are more particularly elucidated hereinbelow:
Component A of the compositions according to the invention are aromatic polycarbonates.
Aromatic polycarbonates in the context of the present invention include not only homopolycarbonates but also copolycarbonates and/or polyestercarbonates; the polycarbonates may be linear or branched in a known manner. Mixtures of polycarbonates may also be used according to the invention.
The thermoplastic polycarbonates, including the thermoplastic aromatic polyestercarbonates, preferably have weight-average molecular weights M. of 15 000 g/mol to 40 000 g/mol, further preferably to 34 000 g/mol, particularly preferably of 17 000 g/mol to 33 000 g/mol, in particular of 19 000 g/mol to 32 000 g/mol, determined by gel permeation chromatography, calibrated against bisphenol A polycarbonate standards using dichloromethane as eluent, calibration with linear polycarbonates (formed from bisphenol A and phosgene) of known molar mass distribution from PSS Polymer Standards Service GmbH, Germany, and calibration by method 2301-0257502-09D (2009 German-language edition) from Currenta GmbH & Co. OHG, Leverkusen. The eluent is dichloromethane. Column combination of crosslinked styrene-divinylbenzene resins. Diameter of the analytical columns: 7.5 mm; length: 300 mm. Particle sizes of the column material: 3 μm to 20 μm. Concentration of the solutions: 0.2% by weight. Flow rate: 1.0 ml/min, temperature of solutions: 30° C. Use of UV and/or RI detection.
The melt volume flow rate MVR of the aromatic polycarbonate used, determined according to ISO 1133:2012-03, at a test temperature of 300° C. and with 1.2 kg load, is preferably 5 to 35 cm3/(10 min), further preferably 6 cm3/(10 min) to 25 cm3/(10 min), further preferably still 6 to 21 cm3/(10 min).
A portion of up to 80 mol %, preferably of 20 mol % to 50 mol %, of the carbonate groups in the polycarbonates used according to the invention may be replaced by aromatic dicarboxylic ester groups. Polycarbonates of this type that incorporate not only acid radicals derived from carbonic acid but also acid radicals derived from aromatic dicarboxylic acids in the molecular chain are referred to as aromatic polyester carbonates. For the purposes of the present invention, they are subsumed within the umbrella term “thermoplastic aromatic polycarbonates”.
Details of the preparation of polycarbonates have been set out in many patent specifications over the past 40 years or so. Reference may be made here by way of example to Schnell, “Chemistry and Physics of Polycarbonates”, Polymer Reviews, Volume 9, Interscience Publishers, New York, London, Sydney 1964, to D. Freitag, U. Grigo, P. R. Müller, H. Nouvertné, BAYER AG, “Polycarbonates” in Encyclopedia of Polymer Science and Engineering, Volume 11, Second Edition, 1988, pages 648-718 and finally to U. Grigo, K. Kirchner and P. R. Müller “Polycarbonate” [Polycarbonates] in Becker/Braun, Kunststoff-Handbuch [Plastics Handbook], volume 3/1, Polycarbonate, Polyacetale, Polyester, Celluloseester [Polycarbonates, Polyacetals, Polyesters, Cellulose Esters], Carl Hanser Verlag Munich, Vienna 1992, pages 117 to 299.
Aromatic polycarbonates are prepared, for example, by reaction of dihydroxyaryl compounds with carbonyl halides, preferably phosgene, and/or with aromatic dicarbonyl dihalides, preferably benzenedicarbonyl dihalides, by the interfacial process, optionally with use of chain terminators and optionally with use of trifunctional or more than trifunctional branching agents. Likewise possible is preparation via a melt polymerization process, by reacting dihydroxyaryl compounds with, for example, diphenyl carbonate.
For the preparation of the polyester carbonates, a portion of the carbonic acid derivatives are replaced by aromatic dicarboxylic acids or derivatives of the dicarboxylic acids, and specifically with aromatic dicarboxylic ester structural units according to the carbonate structural units to be replaced in the aromatic polycarbonates.
Dihydroxyaryl compounds suitable for the preparation of polycarbonates are those of formula (1)
HO—Z—OH (1),
It is preferable for Z in formula (1) to be a radical of formula (2)
Examples of dihydroxyaryl compounds are: dihydroxybenzenes, dihydroxydiphenyls, bis(hydroxyphenyl)alkanes, bis(hydroxyphenyl)cycloalkanes, bis(hydroxyphenyl)aryls, bis(hydroxyphenyl) ethers, bis(hydroxyphenyl) ketones, bis(hydroxyphenyl) sulfides, bis(hydroxyphenyl) sulfones, bis(hydroxyphenyl) sulfoxides, 1,1′-bis(hydroxyphenyl)diisopropylbenzenes and the ring-alkylated and ring-halogenated compounds thereof.
Dihydroxyaryl compounds suitable for the preparation of polycarbonates are for example hydroquinone, resorcinol, dihydroxydiphenyls, bis(hydroxyphenyl)alkanes, bis(hydroxyphenyl)cycloalkanes, bis(hydroxyphenyl) sulfides, bis(hydroxyphenyl) ethers, bis(hydroxyphenyl) ketones, bis(hydroxyphenyl) sulfones, bis(hydroxyphenyl) sulfoxides, α,α′-bis(hydroxyphenyl)diisopropylbenzenes, phthalimidines derived from derivatives of isatin or phenolphthalein, and the ring-alkylated, ring-arylated and ring-halogenated compounds thereof.
Preferred dihydroxyaryl compounds are 4,4′-dihydroxydiphenyl, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 1,1-bis(4-hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, dimethylbisphenol A, bis(3,5-dimethyl-4-hydroxyphenyl)methane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, bis(3,5-dimethyl-4-hydroxyphenyl) sulfone, 2,4-bis(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and also the dihydroxyaryl compounds (I) to (III)
in which each R′ is a C1-to C4-alkyl radical, aralkyl radical or aryl radical, preferably a methyl radical or phenyl radical, very particularly preferably a methyl radical.
Particularly preferred dihydroxyaryl compounds are 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4′-dihydroxydiphenyl and dimethylbisphenol A, and also the bisphenols of formulae (I), (II) and (III).
These and other suitable dihydroxyaryl compounds are described by way of example in U.S. Pat. Nos. 2,999,835 A, 3,148,172 A, 2,991,273 A, 3,271,367 A, 4,982,014 A and 2,999,846 A, in DE 1 570 703 A, DE 2063 050 A, DE 2 036 052 A, DE 2 211956 A and DE 3 832 396 A, in FR 1 561 518 A, in the monograph “H. Schnell, Chemistry and Physics of Polycarbonates, Interscience Publishers, New York 1964”, and in JP 62039/1986 A, JP 62040/1986 A and JP 105550/1986 A.
In the case of the homopolycarbonates, only one dihydroxyaryl compound is used; in the case of the copolycarbonates, two or more dihydroxyaryl compounds are used.
Examples of suitable carbonic acid derivatives include phosgene or diphenyl carbonate.
Suitable chain terminators that may be used in the preparation of the polycarbonates are monophenols. Examples of suitable monophenols include phenol itself, alkylphenols such as cresols, p-tert-butylphenol, cumylphenol, and mixtures thereof.
Preferred chain terminators are the phenols which have substitution by one or more linear or branched, preferably unsubstituted, C1-to C30-alkyl radicals, or by tert-butyl. Particularly preferred chain terminators are phenol, cumylphenol and/or p-tert-butylphenol.
The amount of chain terminator to be used is preferably 0.1 to 5 mol %, based on moles of dihydroxyaryl compounds used in each case. The chain terminators may be added before, during or after the reaction with a carbonic acid derivative.
Suitable branching agents are the trifunctional or more than trifunctional compounds known in polycarbonate chemistry, in particular those having three or more than three phenolic OH groups.
Examples of suitable branching agents include 1,3,5-tri(4-hydroxyphenyl)benzene, 1,1,1-tri(4-hydroxyphenyl)ethane, tri(4-hydroxyphenyl)phenylmethane, 2,4-bis(4-hydroxyphenylisopropyl)phenol, 2,6-bis(2-hydroxy-5′-methylbenzyl)-4-methylphenol, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)propane, tetra(4-hydroxyphenyl)methane, tetra(4-(4-hydroxyphenylisopropyl)phenoxy)methane and 1,4-bis((4′,4″-dihydroxytriphenyl)methyl)benzene and 3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.
The amount of any branching agents to be used is preferably 0.05 mol % to 2.00 mol %, based on moles of dihydroxyaryl compounds used in each case.
The branching agents can either form an initial charge with the dihydroxyaryl compounds and the chain terminators in the aqueous alkaline phase or can be added, dissolved in an organic solvent, before the phosgenation. In the case of the transesterification method, the branching agents are used together with the dihydroxyaryl compounds.
Particularly preferred polycarbonates are the homopolycarbonate based on bisphenol A, the homopolycarbonate based on 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and the copolycarbonates based on the two monomers bisphenol A and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane or the two monomers bisphenol A and 4,4′-dihydroxydiphenyl, and homo- or copolycarbonates derived from the dihydroxyaryl compounds of formulae (I), (II) and/or (III)
The total proportion of the monomer units based on formulae (I), (II), (III), 4,4′-dihydroxydiphenyl and/or bisphenol TMC in the copolycarbonate is preferably 0.1-88 mol %, particularly preferably 1-86 mol %, very particularly preferably 5-84 mol % and in particular 10-82 mol % (based on the sum total of the moles of dihydroxyaryl compounds used).
The relative solution viscosity of the copolycarbonates, determined according to ISO 1628-4:1999, is preferably in the range of 1.15-1.35.
The dihydroxyaryl compounds used, like all the other chemicals and auxiliaries added to the synthesis, may be contaminated with the impurities originating from their own synthesis, handling and storage. It is however desirable to use raw materials of the highest possible purity.
Also preferred are copolycarbonates prepared using diphenols of general formula (4a):
Especially preferred are (poly)siloxanes of formulae (5) and (6)
The siloxane block may likewise preferably be derived from the following structure
where a in formulae (IV), (V) and (VI) is an average number from 10 to 400, preferably 10 to 100 and particularly preferably 15 to 50.
It is likewise preferable when at least two identical or different siloxane blocks of general formulae (IV), (V) or (VI) are joined to one another via terephthalic acid and/or isophthalic acid to form ester groups.
It is likewise preferable when, in formula (4a), p=0, V is C3-alkylene, r=1, Z is C2-alkylene, R8 and R9 are methyl, q=1, W is C3-alkylene, m=1, R5 is hydrogen or C1-to C4-alkyl, preferably hydrogen or methyl, R6 and R7 are each independently C1-to C4-alkyl, preferably methyl, and o is 10 to 500.
Copolycarbonates having monomer units of formula (4a) and in particular also the preparation thereof are described in WO 2015/052106 A2.
Copolycarbonates having monomer units of formula (IV) and in particular also the preparation thereof are described in WO 2015/052106 A2.
Examples of aromatic dicarboxylic acids that are suitable for the preparation of the polyestercarbonates include orthophthalic acid, terephthalic acid, isophthalic acid, tert-butylisophthalic acid, 3,3′-diphenyldicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4-benzophenonedicarboxylic acid, 3,4′-benzophenonedicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid, 2,2-bis(4-carboxyphenyl)propane, trimethyl-3-phenylindane-4,5′-dicarboxylic acid.
Among the aromatic dicarboxylic acids, particular preference is given to using terephthalic acid and/or isophthalic acid.
Derivatives of dicarboxylic acids are dicarbonyl dihalides and dialkyl dicarboxylates, especially dicarbonyl dichlorides and dimethyl dicarboxylates.
Replacement of the carbonate groups by the aromatic dicarboxylic ester groups is substantially stoichiometric, and also quantitative, and the molar ratio of the reactants is therefore also maintained in the final polyestercarbonate. The aromatic dicarboxylic ester groups may be incorporated either randomly or in blocks.
The compositions according to the invention contain at least 70% by weight, preferably at least 70.5% by weight, particularly preferably at least 84% by weight, of aromatic polycarbonate, and are thus based on aromatic polycarbonate.
Component B is a polyalkyl(meth)acrylate. It will be appreciated that this may be one polyalkyl(meth)acrylate or a mixture of various polyalkyl(meth)acrylates. Component B does not include polymers containing polyalkyl(meth)acrylate as part of a graft polymer. The polyalkyl(meth)acrylate is preferably a linear polymer.
The polyalkyl(meth)acrylate according to component B preferably has a weight-average molecular weight of 80 000 to 300 000 g/mol, further preferably of 100 000 to 200 000 g/mol, determined by means of gel permeation chromatography in tetrahydrofuran with PMMA calibration.
Component B may also be a mixture of two or more polyalkyl(meth)acrylates, one of which may also have low molecular weight. The weight-average molecular weight mentioned is then accordingly based on the total component B, the polyalkyl(meth)acrylate mixture. At least one of said polyalkyl(meth)acrylates may have low molecular weight and have a weight-average molecular weight of 1000 to 70 000 g/mol, very particularly preferably 5000 to 60 000 g/mol. The low-molecular-weight polyalkyl(meth)acrylate preferably has a proportion of 2% to 20% by weight, in particular 5% to 10% by weight, based on the total weight of the polyalkyl(meth)acrylate. This makes it possible to improve the processability with the polycarbonate. The weight-average molecular weight stated above of 80 000 to 300 000 g/mol, further preferably 100 000 to 200 000 g/mol, is based on all of the polyalkyl(meth)acrylate present in the composition according to the invention.
The polyalkyl(meth)acrylate preferably has
Very particularly preferably, the polyalkyl(meth)acrylate has at least 60.0% by weight, further preferably still at least 75.0% by weight, in particular at least 85.0% by weight, of repeat methyl methacrylate units.
Exceptionally preferably, the polyalkyl(meth)acrylate comprises 90.0% to 99.0% by weight of methyl methacrylate and 1.0% to 10.0% by weight of methyl acrylate, in each case based on the total weight of the polyalkyl(meth)acrylate.
The proportion of component B in the compositions according to the invention is 4% by weight to 25% by weight, preferably 5% by weight to 22% by weight, further preferably 5% to 20% by weight, in particular to 15% by weight, based on the overall composition.
Component C of the compositions according to the invention is phosphorus-containing flame retardants. It may be a single phosphorus-containing flame retardant, but it may also be a mixture of various phosphorus-containing flame retardants.
Preferred phosphorus-containing flame retardants are cyclic phosphazenes, phosphorus compounds of formula (10), and mixtures thereof:
Preferably, R1, R2, R3 and R4 are independently branched or unbranched C1-to C4-alkyl, phenyl, naphthyl or C1-to C4-alkyl-substituted phenyl. In the case of aromatic R1, R2, R3 and/or R4 groups, these may in turn be substituted by halogen and/or alkyl groups, preferably chlorine, bromine and/or C1-to C4-alkyl, branched or unbranched. Particularly preferred aryl radicals are cresyl, phenyl, xylenyl, propylphenyl or butylphenyl, and also the corresponding brominated and chlorinated derivatives thereof.
X in formula (10) is preferably derived from dihydroxyaryl compounds.
X in formula (10) is particularly preferably
The phosphorus compound of general formula (10) is preferably a compound of formula (11):
in which
Phosphorus compounds of formula (10) are in particular tributyl phosphate, triphenyl phosphate, tricresyl phosphate, diphenyl cresyl phosphate, diphenyl octyl phosphate, diphenyl 2-ethylcresyl phosphate, tri(isopropylphenyl) phosphate, resorcinol-bridged oligophosphate and bisphenol A-bridged oligophosphate. The use of oligomeric phosphoric esters of formula (10) which are derived from bisphenol A is especially preferred.
Further preference is given to using mixtures of identical structure and different chain length, with the stated q value being the average q value. The average q value is determined by determining the composition of the phosphorus compound mixture (molecular weight distribution) by means of high pressure liquid chromatography (HPLC) at 40° C. in a mixture of acetonitrile and water (50:50) and using this to calculate the average values of q.
Particularly preferably, bisphenol A-based oligophosphate (bisphenol A bis(diphenyl phosphate)) according to formula (12) with q=1 to 20, in particular with q=1.0 to 1.2, is present in the compositions according to the invention.
Phosphorus compounds of this kind are known (cf., for example, EP 0 363 608 A1, EP 0 640 655 A2) or can be prepared in an analogous manner by known methods (e.g. Ullmanns EnzyklopAdie der technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry], vol. 18, p. 301 ff., 1979; Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], vol. 12/1, p. 43; Beilstein vol. 6, p. 177).
Just as preferably as the phosphorus compounds according to formula (10), it is possible to use cyclic phosphazenes according to formula (13) as component C:
Particularly preferably used according to the invention are commercially available phosphazenes. These are typically mixtures of rings of different ring sizes.
Further preference is given, either individually or in a mixture, to: propoxyphosphazene, phenoxyphosphazene, methylphenoxyphosphazene, aminophosphazene, fluoroalkylphosphazenes, and also phosphazenes having the following structures:
In the compounds 13a-f shown above, k=1, 2 or 3.
Preferably, the proportion of phosphazenes that are halogen-substituted on the phosphorus, for example composed of incompletely reacted starting material, is less than 1000 ppm, further preferably less than 500 ppm.
The phosphazenes can be used alone or in a mixture. The radical R may always be the same or two or more radicals in the formulae may be different. The radicals R of a phosphazene are preferably identical.
In one embodiment, solely phosphazenes having the same R are used.
Preferably, the proportion of tetramers (k=2) is from 2 to 50 mol %, based on component C, further preferably from 5 to 40 mol %, further preferably still from 10 to 30 mol %, particularly preferably from 10 to 22 mol %.
Preferably, the proportion of higher oligomeric phosphazenes (k=3, 4, 5, 6 and 7) is from 0 to 30 mol %, based on component C, further preferably from 2.5 to 25 mol %, further preferably still from 5 to 20 mol %, and particularly preferably from 6-15 mol %.
Preferably, the proportion of oligomers with k ?8 is from 0 to 2.0 mol %, based on component C, and preferably from 0.10 to 1.00 mol %.
Further preferably, the phosphazenes of component C satisfy all three above-mentioned conditions with respect to the proportions of oligomers.
Particularly preferably present as component C is phenoxyphosphazene (all R=phenoxy, formula 13g), alone or with further phosphazenes according to formula (13) as component C, with a proportion of oligomers with k=1 (hexaphenoxyphosphazene) of 50 to 98 mol %, particularly preferably 60 to 72% by weight, based on the amount of phenoxyphosphazene. If phenoxyphosphazene is used, the proportion of oligomers with k=2 is very particularly preferably: 15% to 22% by weight and with k ?3: 10% to 13% by weight.
Alternatively, component C very particularly preferably comprises, and very particularly preferably is, a phenoxyphosphazene having a trimer proportion (k=1) of 70 to 85 mol %, a tetramer proportion (k=2) of 10 to 20 mol %, a proportion of higher oligomeric phosphazenes (k=3, 4, 5, 6 and 7) of 3 to 8 mol % and phosphazene oligomers with k≥8 of 0.1 to 1 mol %, based on component C.
In an alternative preferred embodiment, n, defined as the arithmetic mean of k, is in the range from 1.10 to 1.75, preferably from 1.15 to 1.50, further preferably from 1.20 to 1.45, and particularly preferably from 1.20 to 1.40 (range boundaries included).
Phosphazenes and the preparation thereof are described, for example, in EP 728 811 A2, DE 1961668 A and WO 97/40092 A1.
The oligomer compositions in the respective blend samples can be detected and quantified after compounding by means of 31P NMR (chemical shift; δ trimer: 6.5 to 10.0 ppm; S tetramer: −10 to −13.5 ppm; δ higher oligomers: −16.5 to −25.0 ppm).
Very particularly preferably, component C comprises bisphenol A-based oligophosphate according to formula (12) and/or cyclic phosphazene according to formula (13), most preferably component C is bisphenol A-based oligophosphate according to formula (12) and/or cyclic phosphazene according to formula (13).
The proportion of phosphorus-containing flame retardant in the compositions according to the invention is 1.5% by weight to 10% by weight, preferably 2% by weight to <8% by weight, particularly preferably to 6% by weight, very particularly preferably to ≤5% by weight, exceptionally preferably to 4% by weight, based on the overall composition. The Vicat temperature decreases significantly with increasing proportion of the phosphorus-containing flame retardant.
The compositions according to the invention contain as component D a fluorine-containing anti-drip agent, which may be a mixture of two or more anti-drip agents. The total amount of anti-drip agent (anti-dripping agent) is 0.3% by weight to 2% by weight, preferably 0.4% by weight to 1% by weight, particularly preferably 0.5% by weight to 1.0% by weight of at least one anti-drip agent.
The anti-drip agent used is preferably fluorine-containing polymer, in particular polyolefin.
The fluorinated polyolefins used with preference as anti-drip agents have high molecular weight and have glass transition temperatures of above −30° C., generally of above 100° C., and fluorine contents preferably from 65% by weight to 76% by weight, in particular from 70% to 76% by weight. Preferred fluorinated polyolefins are polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene/hexafluoropropylene copolymers and ethylene/tetrafluoroethylene copolymers. Fluorinated polyolefins are known (cf. “Vinyl and Related Polymers” by Schildknecht, John Wiley & Sons, Inc., New York, 1962, pages 484-494; “Fluoropolymers” by Wall, Wiley-Interscience, John Wiley & Sons, Inc., New York, volume 13, 1970, pages 623-654; “Modern Plastics Encyclopedia”, 1970-1971, volume 47, No. 10 A, October 1970, McGraw-Hill, Inc., New York, pages 134 and 774; “Modern Plastics Encyclopedia”, 1975-1976, October 1975, volume 52, No. 10 A, McGraw-Hill, Inc., New York, pages 27, 28 and 472 and U.S. Pat. Nos. 3,671,487 A, 3,723,373 A and 3,838,092 A). They can be prepared by known methods, for example by polymerizing tetrafluoroethylene in aqueous medium with a free-radical-forming catalyst, for example sodium, potassium or ammonium peroxodisulfate, at pressures from 7 to 71 kg/cm2 and at temperatures from 0 to 200° C., preferably at temperatures from 20 to 100° C. Further details are described, for example, in U.S. Pat. No. 2,393,967 A.
Depending on the use form, the density of the fluorinated polyolefins can lie between 1.2 and 2.3 g/cm3, preferably 2.0 g/cm3 to 2.3 g/cm3, determined according to ISO 1183-1 (2019-09), and the average particle size between 0.05 and 1000 μm, determined by means of light microscopy or white light interferometry.
Suitable tetrafluoroethylene polymer powders are commercial products and are available by way of example from DuPont under the trade name Teflon®.
Particular preference is given to using polytetrafluoroethylene (PTFE), as such, but also in the form of a PTFE-containing composition, as fluorine-containing anti-drip agent. If a PTFE-containing composition is used, the minimum use amount thereof is preferably enough for at least 0.15% by weight, particularly preferably at least 0.25% by weight, of PTFE to be present in the overall composition. The PTFE-containing compositions include Hostaflon® TF2021 or PTFE blends such as Blendex® B449 (about 50% by weight of PTFE and about 50% by weight of SAN [from 80% by weight of styrene and 20% by weight of acrylonitrile]) from Chemtura. Very particular preference is given to using PTFE or a PTFE/SAN blend as fluorine-containing anti-drip agent.
The polycarbonate compositions according to the invention may contain one or more further additives different from components B, C and D, which are subsumed in the present case under “component E”.
Optionally (0% by weight) up to preferably 12% by weight, further preferably up to 5% by weight, further preferably still up to 3% by weight, in particular 0.1% by weight to 3% by weight, particularly preferably 0.2% by weight to 1% by weight, very particularly preferably 0.5% by weight to 1.0% by weight, of other customary additives (“further additives”) are present, these percentages by weight being based on the total weight of the composition. The group of further additives does not include any phosphorus-containing flame retardant according to component C. The group of further additives in particular also does not include any fluorine-containing anti-drip agent, as this is already described as component D.
Such further additives, as are typically added to polycarbonates, are in particular heat stabilizers, antioxidants, mold-release agents, UV absorbers, IR absorbers, impact modifiers, antistats, flame retardants different from component C, optical brighteners, fillers, light-scattering agents, hydrolysis stabilizers, transesterification stabilizers, (organic) dyes, (organic/inorganic) pigments, compatibilizers and/or additives for laser marking, in particular in the amounts typical for polycarbonate-based compositions. Such additives are described, for example, in EP 0 839 623 A1, WO 96/15102 A 1, EP 0 500 496 A 1 or in “Plastics Additives Handbook”, Hans Zweifel, 5th Edition 2000, Hanser Verlag, Munich. These additives may be added individually or else in a mixture.
Further preferably present as further additives, where further additives are present at all, are one or more further additives selected from the group consisting of heat stabilizers, antioxidants, mold-release agents, organic dyes, organic pigments, inorganic pigments.
The further additive present is very particularly preferably at least one heat stabilizer, an antioxidant and/or a mold-release agent.
It will be appreciated that only such additives may be added, and only in such amounts, where they do not significantly negatively impact the effect according to the invention of high CTI in combination with good flame retardancy and preferably also do not lower the Vicat temperature, determined according to ISO 306:2014-3, VST Method B, below 105° C., further preferably below 110° C.±2° C.
Additives that are particularly preferably present are mold-release agents, further preferably based on a fatty acid ester, further preferably still based on a stearic ester, especially preferably based on pentaerythritol. Particular preference is given to using pentaerythritol tetrastearate (PETS) and/or glycerol monostearate (GMS). If one or more mold-release agents are used, the amount is preferably up to 1.0% by weight (inclusive), further preferably 0.01% to 0.7% by weight, particularly preferably 0.2% to 0.60% by weight, based in each case on the overall composition.
Additives that are particularly preferably present are also heat stabilizers. The amount of heat stabilizer is preferably up to 0.20% by weight, further preferably 0.01% to 0.15% by weight, further preferably still 0.01% to 0.1% by weight, particularly preferably 0.025% to 0.09% by weight, based on the overall composition.
Suitable heat stabilizers are in particular phosphorus-based stabilizers selected from the group of the phosphates, phosphites, phosphonites, phosphines and mixtures thereof. Examples include triphenyl phosphite, diphenyl alkyl phosphite, phenyl dialkyl phosphite, tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite (Irgafos® 168), diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis(2,4-dicumylphenyl) pentaerythritol diphosphite (Doverphos® S-9228), bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, diisodecyloxy pentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tris(tert-butylphenyl) pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4′-biphenylenediphosphonite, 6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphocine, bis(2,4-di-tert-butyl-6-methylphenyl) methyl phosphite, bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyldibenzo[d,g]-1,3,2-dioxaphosphocine, 2,2′,2″-nitrilo[triethyltris(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl) phosphite], 2-ethylhexyl(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl) phosphite, 5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1,3,2-dioxaphosphirane, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, triphenylphosphine (TPP), trialkylphenylphosphine, bisdiphenylphosphinoethane or a trinaphthylphosphine. They are used alone or in a mixture, for example Irganox® B900 (mixture of Irgafos® 168 and Irganox® 1076 (antioxidant) in a 4:1 ratio) or Doverphos® S-9228 with Irganox® B900 or Irganox® 1076. Especially preferably, triphenylphosphine (TPP), Irgafos® 168 or tris(nonylphenyl) phosphite, or mixtures thereof, are used.
It is also possible to use phenolic antioxidants such as alkylated monophenols, alkylated thioalkylphenols, hydroquinones and alkylated hydroquinones. Particular preference is given to using Irganox® 1010 (pentaerythritol 3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate; CAS: 6683-19-8) and Irganox 1076@(octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), preferably in amounts of 0.01%-0.5% by weight.
It is also possible to add sulfonic esters or alkyl phosphates, for example mono-, di- and/or trihexyl phosphate, triisooctyl phosphate and/or trinonyl phosphate, as transesterification inhibitors. The alkyl phosphate used is preferably triisooctyl phosphate (tris-2-ethylhexyl phosphate). It is also possible to use mixtures of various mono-, di- and trialkyl phosphates. Triisooctyl phosphate is preferably used in amounts from 0.003% by weight to 0.05% by weight, further preferably 0.005% by weight to 0.04% by weight and particularly preferably from 0.01% by weight to 0.03% by weight, based on the overall composition.
Examples of impact modifiers are: core-shell polymers such as ABS or MBS; olefin-acrylate copolymers such as for example the Elvaloy® types from DuPont or Paraloid® types from Dow; silicone acrylate rubbers such as for example the Metablen® types from Mitsubishi Rayon Co., Ltd. The compositions according to the invention already have an exceptional profile of properties without additional impact modifiers. Compositions according to the invention are therefore preferably free of impact modifiers.
Particularly preferably, no fillers are present in the compositions according to the invention.
Compositions that are preferred according to the invention consist of
Compositions that are particularly preferred according to the invention consist of
Compositions that are very particularly preferred according to the invention consist of
The phosphorus-containing flame retardant present in this case is preferably either an organophosphate, in particular one of formula (12),
Exceptionally preferred compositions consist of
The polymer compositions according to the invention, containing the mixed components A, B, C, D and optionally E, may be prepared using powder premixes. It is also possible to use premixes of pellet materials or pellet materials and powders with the additions according to the invention. It is also possible to use premixes produced from solutions of the mixture components in suitable solvents, wherein homogenization is optionally effected in solution and the solvent is then removed. In particular, the additives referred to as component E of the compositions according to the invention can be introduced by known methods or in the form of a masterbatch. The use of masterbatches is preferred in particular for the introduction of additives and further constituents, with masterbatches based on the respective polymer matrix being used in particular.
The compositions according to the invention may for example be extruded. After extrusion, the extrudate may be cooled and comminuted. The combining and mixing of a premix in the melt may also be effected in the plasticizing unit of an injection molding machine. In this case, the melt is directly converted into a molded article in the subsequent step.
Compositions according to the invention are preferably used for the production of moldings for components from the EE sector, in particular for high-voltage switches, inverters, relays, electronic connectors, electrical connectors, circuit breakers, components for photovoltaic applications, electric motors, heat sinks, chargers or charging plugs for electric vehicles, electrical junction boxes, smart meter housings, miniature circuit breakers, busbars. The invention thus also provides moldings which are part of a corresponding component. “Part” can be an individual element of a complex product, but equally also the entire element.
A molding in the sense according to the invention is also an insulation layer made from the composition according to the invention. Such a layer can for example be provided on an inverter as a layer to protect against external influences. For inverters, standard insulation materials are those having a CTI of 600 V. The composition according to the invention may also be used as an insulation layer for other electrical components, for example transistors. The insulation layer creates for example a secure separation between the transistor and a metallic heat sink.
The component is preferably designed for an operating voltage of at least 375 V, further preferably at least 400 V, in particular at least 500 V. It can however also be designed for a typical household operating voltage of 230 V±23 V in Europe, although lower distances between the electrical conductors can now be achieved. The molding is preferably used in such a way that the molding itself must have a comparative tracking index of at least 375 V, further preferably at least 400 V, in particular at least 500 V, very particularly preferably at least 600 V, determined as described above.
The invention thus provides moldings consisting of, or comprising regions made from, compositions according to the invention, and also corresponding components comprising elements, i.e. moldings, which consist of compositions according to the invention or comprise regions consisting of compositions according to the invention.
The high comparative tracking index of the polycarbonate compositions according to the invention makes it possible, using the polycarbonate material, to achieve smaller distances between two electrical conductors of a component than was previously possible with the use of polycarbonate.
The invention thus also provides an EE component, comprising a first electrical conductor and a second electrical conductor at a first distance d1 and a second distance d2 with respect to one another,
Such small distances are only achievable with a material that has at least a CTI of 400 V.
“Element made from a thermoplastic composition according to the invention” here means that an element is present which consists of a thermoplastic composition according to the invention, i.e. the composition has not been mixed with additional components.
If the material has a CTI of 600 V, even smaller distances are achievable, such that d1, at the operating voltage listed, is then preferably:
When using a material with a CT of 600 V, dl, at the operating voltage listed, is particularly preferably:
It is well known that the degree of soiling affects the electrical conductivity. The distances d1 and d2 mentioned are usable in practice in components in which, for example due to structural shielding, an IP6K9K degree of protection according to ISO 20653:2013-02 can be adhered to.
Thermoplastic compositions that are preferred according to the invention belong to insulating material group II (400 V≤CTI<600 V), very particularly preferred compositions belong to insulating material group I (600 V≤CTI), classified according to DIN EN 60664-1.
Various embodiments of the present invention are described below:
2. The thermoplastic composition according to embodiment 1, wherein the ratio of the amount of polyalkyl(meth)acrylate in % by weight and the amount of phosphorus-containing flame retardant in % by weight is ≤5.
3. The thermoplastic composition according to embodiment 1 or 2, wherein the phosphorous-containing flame retardant is an organophosphate, a phosphazene or a mixture of these.
4. The thermoplastic composition according to any of the preceding embodiments, wherein, as phosphorus-containing flame retardant, an organophosphate of formula (11) is present
5. The thermoplastic composition according to any of the preceding embodiments, wherein, as phosphorus-containing flame retardant, phosphazene of formula (13g) is present
6. The thermoplastic composition according to any of the preceding embodiments, wherein the composition contains 5% to 20% by weight of polyalkyl(meth)acrylate.
7. The thermoplastic composition according to any of the preceding embodiments, wherein the composition contains 0.3% by weight to 1.0% by weight of mold-release agent.
8. The thermoplastic composition according to any of the preceding embodiments, wherein the composition contains a total of 0.02% to 0.15% by weight of heat stabilizer and/or antioxidant.
9. The thermoplastic composition according to any of the preceding embodiments, wherein the amount of phosphorus-containing flame retardant is 2% to 8% by weight.
10. The thermoplastic composition according to any of the preceding embodiments, wherein component B has a weight-average molecular weight, determined by means of gel permeation chromatography in tetrahydrofuran with PMMA calibration, of 80 000 to 300 000 g/mol.
11. The thermoplastic composition according to any of the preceding embodiments, wherein component B has a weight-average molecular weight, determined by means of gel permeation chromatography in tetrahydrofuran with PMMA calibration, of 100 000 to 200 000 g/mol.
12. The thermoplastic composition according to any of the preceding embodiments, wherein component B has
13. The thermoplastic composition according to any of the preceding embodiments, consisting of
14. The thermoplastic composition according to any of the preceding embodiments, wherein the polyalkyl(meth)acrylate has a number-average molecular weight of 80 000 to 300 000 g/mol, determined in THF with PMMA calibration, and has
15. The thermoplastic composition according to any of the preceding embodiments, wherein the further additives are selected from the group consisting of one or more mold-release agents, heat stabilizers, antioxidants, dyes, pigments, UV absorbers, IR absorbers, optical brighteners, hydrolysis stabilizers, transesterification stabilizers, additives for laser marking, and mixtures thereof.
16. A molding consisting of, or comprising a region made from, a thermoplastic composition according to any of the preceding embodiments.
17. The molding according to embodiment 16, wherein the molding is part of a high-voltage switch, inverter, relay, electronic connector, electrical connector, circuit breaker, a photovoltaic system, an electric motor, a heat sink, a charger for electric vehicles, an electrical junction box, a smart meter housing, a miniature circuit breaker, a busbar.
18. The molding according to embodiment 16 or embodiment 17, wherein the molding is part of an EE component that is designed for an operating voltage of at least 375 V.
19. The molding according to any of embodiments 16 to 18, wherein the molding is part of an EE component that is designed for an operating voltage of at least 400 V.
20. The molding according to any of embodiments 16 to 19, wherein the molding is part of an EE component that is designed for an operating voltage of at least 500 V.
21. The molding according to any of embodiments 16 to 20, wherein the molding is part of an EE component that is designed for an operating voltage of at least 600 V.
22. An EE component, comprising
23. The EE component according to embodiment 22, wherein d1, at the operating voltage U listed below, is:
24. The EE component according to either of embodiments 22 and 23, wherein d2≥1.2 mm.
25. The EE component according to any of embodiments 22 to 24, with an IP6K9K degree of protection according to ISO 20653:2013-02.
26. The EE component according to any of embodiments 22 to 25, designed for an operating voltage of at least 400 V, preferably of at least 500 V, particularly preferably of at least 600 V.
27. The EE component according to any of embodiments 22 to 26, wherein the element made from a thermoplastic composition according to any of embodiments 1 to 15 is a molding according to any of embodiments 16 to 21.
28. The use of the combination of 4% to 25% by weight of polyalkyl(meth)acrylate, 0.3% to 2% by weight of fluorine-containing anti-drip agent and 1.5% to 10% by weight, preferably 2% to 8% by weight, of phosphorus-containing flame retardant, wherein the % by weight figures are based on the resulting overall composition, for attaining a CTI of 600 V and a UL94 V0 classification at 2 mm in a thermoplastic, polycarbonate-based composition.
29. The thermoplastic composition according to any of the preceding embodiments 1 to 15, the molding according to any of the preceding embodiments 16 to 21, the EE component according to any of embodiments 22 to 27 or the use according to 28, wherein the aromatic polycarbonate is bisphenol A-based homopolycarbonate.
Component A-1: Linear polycarbonate based on bisphenol A having a melt volume flow rate of 12 cm3/(10 min) (according to ISO 1133:2012-03, at a test temperature of 300° C. and with 1.2 kg load) containing as component E-3 250 ppm (=0.025% by weight, based on the total weight of component A) of triphenylphosphine heat stabilizer.
Component A-2: Linear polycarbonate based on bisphenol A having a melt volume flow rate of 6 cm3/(10 min) (according to ISO 1133:2012-03, at a test temperature of 300° C. and with 1.2 kg load).
Component B-1: Polyalkyl(meth)acrylate having a glass transition temperature of 117° C., measured according to ISO 11357-1/-2, with 1% by weight methyl acrylate proportion, Mw: 147 000 g/mol, determined by means of gel permeation chromatography in tetrahydrofuran with PMMA calibration, available under the trade name Plexiglas® 8H from Rohm GmbH.
Component C-1: Organophosphate of formula (12) with q=1.0-1.2. Bisphenol A bis(diphenyl phosphate) from Adeka.
Component C-2: Rabitle FP110 phenoxycyclophosphazene from Fushimi Pharmaceutical, Japan, formula (13g), with a trimer proportion (k=1) of approximately 68 mol %.
Component D-1: ADS5000 SAN-encapsulated polytetrafluoroethylene (approx. 50% by weight PTFE (fluorine-containing anti-drip agent) and approx. 50% by weight SAN) from Chemical Innovation Co., Ltd. Thailand.
Component E-1: Mold-release agent. Pentaerythritol tetrastearate, commercially available as Loxiol VPG 861 from Emery Oleochemicals Group.
Component E-2: Mixture of heat stabilizer and antioxidant. Irganox® B900 from BASF (mixture of Irgafos® 168 (tris(2,4-di-tert-butylphenyl) phosphite) and Irganox® 1076 (octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) in a 4:1 ratio by weight).
In order to determine the comparative tracking index, the compositions described here were tested according to the rapid test method based on IEC 60112:2009. To this end, a 0.1% ammonium chloride test solution (395 ohm*cm resistance) was applied dropwise, between two neighboring electrodes spaced apart by 4 mm, to the surface of test specimens of dimensions 60 mm×40 mm×4 mm at a time interval of 30 s. A test voltage was applied between the electrodes and was varied over the course of the test. The first test specimen was tested at a starting voltage of 300 V or 350 V. A maximum of 50 drops (one drop every 30 s) in total were applied per voltage as long as no tracking current >0.5 A over 2 s occurred or the sample burned. After 50 drops, the voltage was increased by 50 V and a new test specimen was tested at this higher voltage, according to the procedure described above. This process was continued until either 600 V was reached or a tracking current or burning occurred. If one of the above-mentioned effects already occurred with fewer than 50 drops, the voltage was reduced by 25 V and a new test specimen was tested at this lower voltage. The voltage was reduced until the test was passed with 50 drops without tracking current or burning. This procedure was therefore used to determine the maximum possible voltage at which a composition was able to withstand 50 drops of the test solution without occurrence of a tracking current. Lastly, four further test specimens were tested at the determined maximum voltage with 50 drops each for confirmation. This confirmed value is reported as the CTI in the examples. A 100-drop value was not determined, hence “rapid test method based on” the specified standard.
The PTI is tested based on IEC 60112:2009, modified as described below. To this end, a 0.1% ammonium chloride test solution (395 ohm*cm resistance) was applied dropwise, between two neighboring electrodes spaced apart by 4 mm, to the surface of test specimens of dimensions 60 mm×40 mm×4 mm at a time interval of 30 s. In contrast to the CT testing, in the PTI testing a fixed test voltage is applied between the electrodes and a total of 5 test specimens are tested at the respective voltage. A maximum of 50 drops (one drop every 30 s) in total were applied per test specimen as long as no tracking current >0.5 A over 2 s occurred or the sample burned.
The flame retardancy of the polycarbonate compositions was tested according to Underwriters Laboratories method UL 94 V in thicknesses of 1.5 mm and 2 mm. The tested test bars were conditioned beforehand for 7 days at 20% relative humidity and 70° C. ambient temperature.
Various fire classes are assigned depending on the behavior of the test specimens. This includes the time until the flame is extinguished, resistance to dripping, or whether a material produces burning drips. The classes determined hereafter are designated V0, V1 and V2 and are ascertained on the basis of a total of five tested test specimens.
V0: The test specimen, positioned with its longitudinal axis 180° (vertical) to the flame, has an average afterflame time after removal of the flame of not more than 10 s and does not produce any dripping plastic particles that ignite cotton wool located under the test specimen. The total afterflame time of five test specimens, in each case with two times flame application, is at most 50 s.
V1: In contrast to V0, the average maximum afterflame time here is <30 s, and here too no dripping particles or ignition of the cotton wool are permitted. The total afterflame time of five test specimens, in each case with two times flame application, is <250 s.
V2: In contrast to V0 and V1, dripping plastic particles that ignite the cotton wool are formed in this classification. The individual afterflame times are <30 s and the total afterflame time of 5 test specimens, in each case with two times flame application, is <250 s.
f.: The test does not deliver a flame retardancy classification if the afterflame times are exceeded.
The heat distortion resistance of the compositions was determined on the basis of the Vicat softening temperature (method B, test force 50 N, heating rate 50 K/h) on test specimens having the dimensions 80 mm×10 mm×4 mm according to ISO 306:2014-3.
The compositions were prepared on a 25 mm twin-screw extruder from Coperion with a throughput of 20 kg/h. The temperatures of the polymer melt in the extruder were between 260-280° C. with an average screw speed of 225 rpm.
The test specimens having the dimensions 60 mm×40 mm×4 mm were produced from the molding compounds using standard injection molding methods at a melt temperature of 280° C. and a mold temperature of 80° C.
In the tables below, “n.t.” means “not tested” and “f.” means “failed”. The “*” means “taken from UL Yellow Card”.
Pure bisphenol A-based polycarbonate has a CTI of 250 V without mold-release agent (V-1) and an inherent flame retardancy V2, measured according to UL94. As the results from Table 1, but also from Table 2, show, the addition of 5% by weight of polyalkyl(meth)acrylate already leads to a significant improvement in the comparative tracking index of polycarbonate, however also to a significant deterioration in the flame retardancy (cf. V-1 and V-6). Although V-3 and V-4 achieve a result of 600 V in the CTI rapid testing, the robustness of these compositions is significantly worse than those with additional PMMA. This is especially evident in the PTI measurement, which tests a higher number of test specimens at defined voltage (operating voltage) and shows the weak points in terms of the voltage ranges. In this case, compositions without PMMA are prone to failure in particular at 300 V and 350 V, but are robust at a higher voltage of 600 V. A comparable, PMMA-containing composition (E-14) exhibits this robustness also at low voltages of 300 V and 350 V (see Table 2).
The addition of mold-release agent and heat stabilizer has a negative effect in the polycarbonate compositions on the Vicat softening temperature and on the fire performance, with only a slight improvement in the CTI (see V-2). The flame retardancy of the composition however does not improve with addition of polyalkyl(meth)acrylate, and even worsens (V-6), with the result that additional flame retardant additives also have to be added in this case. As V-5 shows, the sole addition of phosphorus-containing flame retardant is not sufficient to achieve a V0, however it significantly lowers the CTI. It is only the combination of anti-drip agent with phosphorus-containing flame retardant and polyalkyl(meth)acrylate that can ultimately achieve the desired profile of properties consisting of high CTI, good flame retardancy, robustness of the CTI, and also still sufficiently high Vicat temperature (see E-7 to E-9). In addition to BDP, this is also found with phosphazene (E-10) as flame retardant.
Even higher amounts of polyalkyl(meth)acrylate have a positive effect on the CTI, the fire performance becoming significantly worse with increasing content of PMMA. Although a CTI of 600 V is achieved with 10% by weight and with 20% by weight of polyalkyl(meth)acrylate, the addition of at least 2% by weight of flame retardant (E-12), in combination with anti-drip agent, is necessary for achieving a V0 classification according to UL 94 V. As E-16 shows, this is also achieved with phosphazene instead of BDP as flame retardant. The addition of mold-release agent and heat stabilizer (cf. E-13 and E-15) has an adverse effect on the result only, as already described above, in terms of the Vicat softening temperature. From 20% by weight of polyalkyl(meth)acrylate, a V0 classification can only be achieved with relatively large amounts of flame retardant (cf. V-18 with V-20 and V-21). Increasing the amount of anti-drip agent in the case of high polyalkyl(meth)acrylate contents does not have any further effect in terms of flame retardancy (V-19). As the results from Table 1 and 2 show, the ratio of polyalkyl(meth)acrylate to phosphorus-containing flame retardant should preferably be at most 5. A smaller ratio and thus more flame retardant does not cause any problems in terms of the CTI, but at the same time does mean significantly lower Vicat temperatures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22164387.7 | Mar 2022 | EP | regional |
This application is the United States national phase of International Patent Application No. PCT/EP2023/057007 filed Mar. 20, 2023, and claims priority to European Patent Application No. 22164387.7 filed Mar. 25, 2022, the disclosures of which are hereby incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/057007 | 3/20/2023 | WO |
