Multilayer structure suitable for use as a reflector

Abstract

A multilayer structure based on polycarbonate compositions with fillers is described, which has a metal layer as a reflective layer and has balanced property conditions of CLTE, CLTE ratio, thermal conductivity and gloss. This multilayer structure is particularly useful as a reflector or as a mirror element in head-up displays. Containing expanded graphite and fused silica as fillers. In the compositions provided according to the invention, no additional heat sink is required when implementing the component.

Description

[0001] The present invention relates to a layer arrangement comprising a substrate layer and a metal layer, wherein the substrate layer has a high surface quality, a minimized coefficient of thermal expansion and a good thermal conductivity. The thermoplastic substrate layer consists of a polycarbonate-based composition.

[0002] Due to their high heat distortion resistance, polycarbonate-based molding compounds, in particular copolycarbonate-based molding compounds, are particularly suitable for components exposed to high ambient temperatures and potential "hot spots". In particular, headlamp reflectors and other components in headlamps, as well as mirror optics in, for example, head-up displays installed in the interior of a car, are subjected to high temperatures due to the radiant heat of the lighting devices (e.g. semiconductor LEDs, xenon lamps, halogen lamps) or via solar radiation, where neither their thermal-mechanical properties nor their shape are allowed to change.

[0003] Temperature stability means, in particular, that the material properties do not change significantly in the case of temperature changes (in particular hot spots caused by solar radiation). For polymers, this property is achieved by the addition of usually large amounts of fillers having a low coefficient of thermal expansion.

[0004] However, the use of large amounts of fillers in polycarbonates leads to a significant reduction in flow properties, which in turn places certain limits on the processability of the material. This is particularly problematic for substrate layers of challenging component geometries (from monolithic to multi-mirror designs with increasingly smaller functional units), for example for headlamp reflectors.

[0005] Since headlamp reflectors are also components with extremely high quality requirements for the metal surface, the substrate layer thereunder must also have an extremely high surface quality, which is based on the roughness of the substrate surface and the gloss measurement associated therewith. As described in EP 2 785 794 A1, only through a special processing operation - dynamic mold temperature control - can the extremely high surface quality of the filler-containing material be ensured compared to the filler-free polymer. Here, depending on the filler type and filler content, different qualities can be achieved.

[0006] The stability of the component thermal expansion and the associated light-optical projection, which is crucial in reflectors and head-up displays, also depends on the material's inherent heat distribution / dissipation capacity. This property is almost non-existent in pure polymers (insulators). Here, too, the thermal conductivity of the entire molding compound can be significantly improved by the addition of suitable fillers, which have a high thermal conductivity themselves. However, the addition of the corresponding fillers to conventional compositions, even with dynamic mold temperature control, is at the expense of the highest achievable surface quality. In addition, depending on the amount and type of filler, the flow behavior of the polymer melt, which can be measured based on the melt viscosity of the molding compound, and the ductility of the molded part are also significantly deteriorated.

[0007] Due to the increasing requirements for the design and performance of automotive headlamps, there is a tendency towards multilayer hybrid structures. Such structures comprise a layer or body made of a metallic material, for example aluminum or magnesium, which acts as a heat sink (heat sink), a thermoplastic material applied thereon and having a high surface quality and a further reflective layer made of metal. When combining these materials, the thermoplastic material should have a similar coefficient of thermal expansion as the metal in order to achieve as synchronous as possible thermally induced warping and thus ensure permanent adhesion. In the present case, this can only be achieved by highly filled thermoplastic plastics, since metals, for example aluminum, have an expansion coefficient of < 30 ppm / K, whereas pure thermoplastic plastics have a thermal expansion coefficient of > 60 ppm / K. The possibility of replacing such metal-thermoplastic hybrid is the combination of two (identical or different) thermoplastic plastics, one of which must have a very high thermal conductivity and thus act as a heat sink. The second material is filler-free and thus provides the necessary surface quality for the reflective layer.

[0008] However, the inventors of the present application have realized a further idea for an alternative component in its functionality which is significantly more attractive in terms of component production and in terms of later recyclability. If a material can be found which has both the thermal conductivity required as a heat sink and at the same time provides the surface quality required for a surface material, it is possible to produce a new type of reflector in single-component injection molding and subsequent metallization.

[0009] However, the challenge lies in the combination of all the above-mentioned properties: In particular for high-precision optics based on LED and laser technology today, the maximization of light stability is a central feature for greater safety in road traffic. The requirement for the corresponding flowability of the material and the realizability of more complex geometries and thus more innovative designs also places high demands on such materials. In addition, it must be possible to realize a surface with a high surface quality. The aim is therefore to provide a corresponding layer arrangement, also referred to as layer structure, which meets the above-mentioned requirements and is simpler in its structure than the conventional multilayer hybrid structure with its above-mentioned three basic core layers. Here, it has surprisingly been found that using a specific thermoplastic composition makes it possible to realize this by means of the single-component injection molding technique under dynamic mold tempering and subsequent metallization.

[0010] The subject matter of the present invention is therefore a layer structure, comprising

[0011] i) a base layer made of a thermoplastic polycarbonate-based composition, which contains

[0012] a) 44 to 63% by weight of an aromatic polycarbonate,

[0013] b) 3 to 8% by weight of expanded graphite,

[0014] c) 34 to 38% by weight of fused silica,

[0015] d) 0 to 10 wt.-% of one or more additional additives,

[0016] wherein the total amount of expanded graphite and fused silica is at least 40 wt.-%,

[0017] and

[0018] ii) a metal layer applied to the base layer i.

[0019] The total amount of expanded graphite and fused silica according to components b and c, i.e. the sum of their individual amounts, is preferably at least 42 wt.-%, more preferably at least 42.5 wt.-%, particularly preferably at least 44 wt.-%, very particularly preferably at least 45 wt.-%.

[0020] By "base layer made of a thermoplastic... composition" is meant that the base layer consists of this composition or comprises sub-areas consisting of this composition. The base layer preferably consists of this composition.

[0021] For the present invention, "layer structure" means the sequence of at least layers i and ii, i.e. two layers, which can also be expressed in the term "multilayer structure". In principle, further layers are also possible, but the layer structure preferred according to the invention comprises only layers i and ii.

[0022] A preferred layer structure according to the invention is a layer structure wherein the thermoplastic polycarbonate-based composition of the base layer i contains the following components

[0023] a) 54 to 60 wt.-% of an aromatic polycarbonate,

[0024] b) 5 to 7.5 wt.-% of expanded graphite,

[0025] c) 35 to 37.5 wt.-% of fused silica,

[0026] d) 0 to 5 wt.-% of one or more additional additives.

[0027] A particularly preferred layer structure according to the invention comprises

[0028] i) a base layer made of a thermoplastic polycarbonate-based composition, and

[0029] ii) a metal layer applied to the base layer i, wherein

[0030] The thermoplastic polycarbonate-based composition of the base layer i consists of

[0031] a) 54 to 60 wt.-% of an aromatic polycarbonate,

[0032] b) 5 to 7.5 wt.-% of expanded graphite, very particularly preferably having a D(0.5) of the expanded graphite of 700 to 1200 pm, determined by sieve analysis according to DIN 51938:2015-09,

[0033] c) 35 to 37.5 wt.-% of fused silica, very particularly preferably having a D(0.5) of the fused silica of 3 to 5 pm, determined according to ISO 13320:2009-10,

[0034] d) 0 to 5 wt.-% of one or more additional additives,

[0035] wherein the total amount of expanded graphite and fused silica is at least 40 wt.-%, in particular at least 42 wt.-%, wherein the additives contained are very particularly preferably at least one heat stabilizer, at least one mold release agent and carbon black, wherein it is extremely preferred that no additional additives are contained.

[0036] The layer structure according to the application can be a constituent element for various different applications.

[0037] Such a layer structure is preferably part of or forms a reflector. Together with a light source and optionally a cover or optionally a housing, for example a headlamp housing, it is part of a lighting device, wherein the reflector is arranged such that at least part of the light emitted by the light source is reflected by the reflector. One example of such a lighting device is a headlamp, for example used as a vehicle headlamp in a motor vehicle. According to the application, the assembly is likewise preferably a mirror element of a head-up display. The purpose of such a mirror element in a head-up display is to project a desired image onto a windshield pane.

[0038] It is to be appreciated that one or more additional layers can also be part of the layer structure in addition to the base layer and the metal layer. These layers are in particular protective layers. The layer structure according to the application preferably does not contain further layers in addition to the base layer, the metal layer and the one or more protective layers.

[0039] Preferred embodiments of the layer structure are described below, in particular also with regard to the thermoplastic polycarbonate-based composition. It is to be appreciated that the preferred embodiments can be combined with one another if no contrary statement is made.

[0040] The subject matter of the present application is likewise a method for producing the layer structure. This method comprises the following steps

[0041] a) forming the base layer from the thermoplastic polycarbonate-based composition described elsewhere in this application by means of single-component injection molding under dynamic mold temperature, and then

[0042] b) applying the metal layer to this base layer.

[0043] The metal layer acts as a reflective layer, which at least partially reflects light in the wavelength range from 380 nm to 750 nm. In the simplest case, the metal layer is designed to be completely reflective like a mirror layer.

[0044] It can be, for example, an aluminum layer or a noble metal layer. The layer can be applied by chemical methods, in particular chemical vapor deposition (CVD) or electroplating, or by physical methods, in particular physical vapor deposition (PVD) or sputtering. These methods are described in more detail, for example, in "Vakuumbeschichtung Bd. 1 bis 5", H. Frey, VDI-Verlag Düsseldorf 1995 or "Vakuumbeschichtung Bd. 6 bis 10", H. Frey, VDI-Verlag Düsseldorf 1995. Dünnschicht-Technologie", Part 1, R. A. Haefer, Springer Verlag 1987.

[0045] The reflective layer, i.e. the metal layer, of the layer structure according to the application preferably has a thickness determined by means of atomic force microscopy of > 10 nm to < 1000 nm, more preferably of > 50 nm to < 800 nm, particularly preferably of > 60 nm to < 500 nm, very particularly preferably of > 60 nm to < 300 nm. This is the total thickness of the metal layer. If, for example, two layers made of different metals are stacked on one another, the thickness of the metal layer of the layer structure is the sum of the thicknesses of the two layers.

[0046] In order to achieve better adhesion of the metal and in order to clean the substrate surface, the surface to be coated can be subjected to a plasma pretreatment. Plasma pretreatment can in some cases change the surface properties of polymers. These methods are described, for example, by Friedrich et al. in "Metallized plastics 5&6: Fundamental and applied aspects" and by H. Grüünwald et al. in "Surface and Coatings Technology, 111 (1999), 287-296". However, a plasma pretreatment is not necessary for the production of the layer structure according to the application.

[0047] The metal layer preferably contains at least one element selected from Ag, Al, Au, Pt, Fe, Cr, Sn, In, Ti, Pd, Nb, Cu, V, stainless steel or alloys thereof. Preferably, the layer is an aluminum, silver, gold, palladium or copper layer, particularly preferably a silver or aluminum layer.

[0048] The metal layer completely or partially covers the substrate layer. If the metal layer only partially covers the substrate layer, at least 60%, preferably at least 70%, more preferably at least 80%, particularly preferably at least 90% of the substrate layer is covered by the metal layer.

[0049] To prevent oxidation or other damage, one or more additional layers, etc., which form a protective layer, can be provided for the metal layer. To this end, the metal layer is optionally preferably surrounded on one or both sides by one or more metal oxide or metal nitride layers, which enable uniform deposition of the metal and / or protect the metal as a protective layer (also referred to herein as a sacrificial layer). Suitable oxides and / or nitrides are, inter alia, aluminum oxide, titanium dioxide, silicon oxide SiO x , tantalum pentoxide Ta2O5, zirconium oxide, zirconium dioxide, niobium oxide, hafnium oxide, zinc tin oxide, indium tin oxide, aluminum zinc oxide, silicon nitride, boron nitride or titanium nitride. However, these layers do not belong to the metal layer.

[0050] Alternatively or additionally, it is conceivable to consider a protective layer which is different from a metal oxide or metal nitride layer, which protects the metal layer or the metalloid layer from external influences, i.e. protects them from corrosion or from other external influences, such as detergents, scratches, etc. Such a protective layer can be applied in a PECVD (plasma-enhanced chemical vapor deposition) method or a plasma polymerization method. Here, low-boiling precursors, in particular siloxane-based precursors, are vaporized into the plasma and thus activated so that they can form a film. Typical substances here are hexamethyldisiloxane (HMDSO), tetramethyldisiloxane, decamethylcyclopentasiloxane, octamethylcyclotetrasiloxane and trimethoxymethylsilane, of which hexamethyldisiloxane is particularly preferred. Very particularly preferably, the protective layer is a layer containing hexamethyldisiloxane (HMDSO). The total thickness of the protective layer is preferably here a maximum of 100 nm, more preferably less than 100 nm, particularly preferably less than 50 nm, very particularly preferably less than 35 nm.

[0051] Preferably, the one / more protective layer(s) is / are followed by no further layer, or when no protective layer is present, which is a preferred embodiment in the case of a metal layer of gold and / or platinum. The protective layer is also not absolutely necessary in the layer structure according to the application, so that in one embodiment no protective layer is applied to the metal layer. The layer structure according to the application is preferably a structure formed only of layers i and ii. For use in applications such as reflectors, no heat dissipation element is required in the composition provided, but rather a plurality of functions is achieved by the multilayer structure according to the application.

[0052] Various modifications can be made to the layer structure described above. For example, two silver layers can be used or different layer thicknesses can be used.

[0053] The layer structure can be planar and thus act as a simple mirror. However, according to a further embodiment, the layer structure is designed to be non-planar. The layer structure can then act as a converging mirror or a diverging mirror. The layer structure may, for example, be designed as a paraboloid of revolution.

[0054] The application of the layer structure according to the application is a headlamp reflector and a mirror optic in a head-up display, for example. The subject matter of the application is therefore likewise a headlamp reflector or a mirror optic in a head-up display comprising a layer structure according to the application.

[0055] Thermoplastic substrate layer

[0056] The components of the thermoplastic composition of the substrate layer are described below. It is to be appreciated that the % by weight values are in each case based on the total weight of the respective composition.

[0057] It is further appreciated that the components used can contain typical impurities, for example from their production process. It is preferred to use the components as pure as possible. It is further appreciated that these impurities can also be contained in the closed formulation of the composition. They are then included in the respective weight proportion of the component from which they originate and should be taken into account in the stated weight proportions.

[0058] Component a

[0059] Component a of the composition is an aromatic polycarbonate.

[0060] The aromatic polycarbonates in the present application include not only homopolycarbonates, but also copolycarbonates and / or polyester carbonates; the polycarbonates can be linear or branched in a known manner. Mixtures of polycarbonates can also be used according to the application.

[0061] The thermoplastic polycarbonate preferably has a weight average molecular weight Mw, determined by gel permeation chromatography, of from 15 000 g / mol to 40 000 g / mol, more preferably to 34 000 g / mol, particularly preferably from 17 000 g / mol to 33 000 g / mol, in particular from 19 000 g / mol to 32 000 g / mol. w with calibration against bisphenol A polycarbonate standards using dichloromethane as eluent, calibration with linear polycarbonates (formed from bisphenol A and phosgene) having a known molar mass distribution from PSS Polymer Standards Service GmbH, Germany, calibration by method 2301-0257502-09D (German version 2009) from Currenta GmbH & Co. OHG, Leverkusen. Eluent is dichloromethane. Column combination of crosslinked styrene-divinylbenzene resin. Diameter of analytical column: 7.5 mm; length: 300 mm. Particle size of column material: 3 pm to 20 pm. Concentration of solution: 0.2% by weight. Flow rate: 1.0 ml / min, solution temperature: 30°C. UV and / or RI detection is used.

[0062] A portion of up to 80 mole %, preferably 20 to 50 mole %, of the carbonate groups in the polycarbonates used according to the application can be replaced by aromatic dicarboxylate groups. Such polycarbonates which incorporate not only acid moieties derived from carbonic acid but also acid moieties derived from aromatic dicarboxylic acids in the molecular chain are referred to as aromatic polyester carbonates. For the purposes of the present application, they are subsumed under the generic term "thermoplastic aromatic polycarbonates".

[0063] The polycarbonates are produced in known manner from dihydroxyaryl compounds, carbonic acid derivatives, optionally chain terminators and optionally branching agents, wherein, in order to produce polyester carbonates, a portion of the carbonic acid derivatives is replaced by aromatic dicarboxylic acids or dicarboxylic acid derivatives, in particular according to the extent of the carbonate structural units in the aromatic polycarbonates which are to be replaced by aromatic dicarboxylate structural units.

[0064] Dihydroxyaryl compounds which are suitable for the production of polycarbonates are those of the formula (1)

[0065] HO-Z-OH (1),

[0066] wherein

[0067] Z is an aromatic radical having 6 to 30 carbon atoms and can contain one or more aromatic rings, can be substituted and can contain aliphatic or cycloaliphatic radicals or alkylaryl radicals or heteroatoms as bridging elements.

[0068] Z in the formula (1) is preferably a radical of the formula (2)

[0069]

[0070] wherein

[0071] R 6 and R 7 are, independently of one another, H, C1- to C 18 -alkyl, C1- to C 18 -alkoxy, halogen, such as CI or Br, or in each case optionally substituted aryl or aralkyl, preferably H or C1- to C 12 -alkyl, particularly preferably H or C1- to C8-alkyl, very particularly preferably H or methyl, and

[0072] X is a single bond, -SO2-, -CO-, -O-, -S-, C1- to C6-alkylene, C2- to C5-alkylidene or C5- to C6-cycloalkylidene, which can be substituted by C1- to C6-alkyl, preferably methyl or ethyl, or is C6- to C 12 -arylene which can optionally be fused to further heteroatom-containing aromatic rings.

[0073] X is preferably a single bond, C1- to C5-alkylene, C2- to C5-alkylidene, C5- to C6-cycloalkylidene, -O-, -SO-, -CO-, -S-, -SO2- or a radical of the formula (3)

[0074]

[0075] Examples of dihydroxyaryl compounds are: dihydroxybenzene, dihydroxydiphenyl, bis(hydroxyphenyl)alkane, bis(hydroxyphenyl)cycloalkane, bis(hydroxyphenyl)arene, bis(hydroxyphenyl)ether, bis(hydroxyphenyl)ketone, bis(hydroxyphenyl)sulfide, bis(hydroxyphenyl)sulfone, bis(hydroxyphenyl)sulfoxide, 1,1 '-bis(hydroxyphenyl)diisopropylbenzene, and their alkylated and halogenated on the ring compounds.

[0076] Suitable dihydroxyaryl compounds for the production of polycarbonates and copolycarbonates used according to the application are, for example, hydroquinone, resorcinol, dihydroxydiphenyl, bis(hydroxyphenyl)alkane, bis(hydroxyphenyl)cycloalkane, bis(hydroxyphenyl)sulfide, bis(hydroxyphenyl)ether, bis(hydroxyphenyl)ketone, bis(hydroxyphenyl)sulfone, bis(hydroxyphenyl)sulfoxide, α,α'-bis(hydroxyphenyl)diisopropylbenzene, and their alkylated, alkylated on the ring and halogenated on the ring compounds. Copolycarbonates can also be produced using Si-containing telechelic polymers to obtain so-called Si-copolycarbonates.

[0077] Preferred dihydroxyaryl compounds are 4,4'-dihydroxydiphenyl, 2,2-bis(4-hydroxyphenyl)- 1 -phenylpropane, 1,1 -bis(4-hydroxyphenyl)phenylethane, 2,2-bis(4-hydroxyphenyl)propane, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 1,3-bis[2-(4-hydroxyphenyl)-2- propyl]benzene (Bisphenol M), 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 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, 1,3-bis[2-(3,5-dimethyl-4-hydroxyphenyl)-2-propyl]benzene and 1,1 - bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (Bisphenol TMC), and the bisphenols of the formulae (I) to (III)

[0078]

[0079] wherein R' each represents C1- to C4-alkyl, aralkyl or aryl, preferably methyl or phenyl, very particularly preferably methyl.

[0080] Particularly preferred dihydroxyaryl compounds are 4,4'-dihydroxydiphenyl, 1,1 -bis(4- hydroxyphenyl)phenylethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4- hydroxyphenyl)propane, 1,1 -bis(4-hydroxyphenyl)cyclohexane and 1,1 -bis(4- hydroxyphenyl)-3,3,5-trimethylcyclohexane (Bisphenol TMC), and the dihydroxyaryl compounds of the formulae (I), (II) and / or (III).

[0081] These and other suitable dihydroxyaryl compounds are described, for example, in US 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, German Offenlegungsschriften 1 570 703 A, 2 063 050 A, 2 036 052 A, 2 211 956 A and 3832 396 A, French Patentschrift 1 561 518 A1, the monograph "H. Schnell, Chemistry and Physics of Polycarbonates, Interscience Publishers, New York 1964, pages 28 ff.; pages 102 ff." and "D.G. Legrand, J.T. Bendler, Handbook of Polycarbonate Science and Technology, Marcel Dekker New York 2000, pages 72 ff.".

[0082] In the case of homopolycarbonates, only one dihydroxyaryl compound is used; in the case of copolycarbonates, two or more dihydroxyaryl compounds are used.

[0083] Particularly preferred polycarbonates are homopolycarbonates based on bisphenol A, homopolycarbonates based on 1,1 -bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 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 homopolymers or copolymers derived from the dihydroxyaryl compounds of the formulae (I), (II) and / or (III), which in particular comprise bisphenol A

[0084]

[0085] where R' each is Ci- to C4-alkyl, aralkyl or aryl, preferably methyl or phenyl, very particularly preferably methyl.

[0086] The total proportion of monomeric units based on formula (I), (II), (III), 4,4'-dihydroxydiphenyl and / or bisphenol TMC in the copolycarbonates is preferably 0.1 to 88 mol%, particularly preferably 1 to 86 mol%, very particularly preferably 5 to 84 mol%, in particular 10 to 82 mol% (based on the sum of the moles of the dihydroxyaryl compounds used).

[0087] The dihydroxyaryl compounds used, like all other chemicals and auxiliaries added to the synthesis, can be contaminated with pollutants from their own synthesis, handling and storage. However, it is desirable to work with as pure raw materials as possible.

[0088] The copolycarbonates can exist as block copolycarbonates and random copolycarbonates. Random copolycarbonates are particularly preferred.

[0089] Here, the frequency of the diphenolat monomeric units in the copolycarbonates is derived from the molar ratio of the dihydroxyaryl compounds used.

[0090] The relative solution viscosity of the copolycarbonates is preferably 1.15 to 1.35, determined according to ISO 1628-4:1999.

[0091] The monofunctional chain terminators required for the adjustment of the molecular weight, such as phenols or alkylphenols, in particular phenol, p-tert-butylphenol, isooctylphenol, cumylphenol, their chloroformates or acyl chlorides of monocarboxylic acids or mixtures of these chain terminators, are supplied to the reaction together with the one or more diphenolat or added to the synthesis at any time, as long as there is still phosgene or chloroformate end groups in the reaction mixture, or, in the case of acyl chlorides and chloroformates as chain terminators, as long as a sufficient amount of phenolic end groups can be provided for the polymer formed. However, it is preferred to meter the one or more chain terminators after the phosgenation at a point or time at which no phosgene is present any more but the catalyst has not yet been metered, or they are metered before the catalyst or together with the catalyst or in parallel.

[0092] The branching agents or branching agent mixtures that can be used are added to the synthesis in the same way, but generally before the chain terminators. Generally, a triphenol, a tetraphenol, or an acyl chloride of a tri- or tetracarboxylic acid, or a mixture of polyphenols or a mixture of acyl chlorides is used.

[0093] Examples of some compounds which can be used as branching agents and which have three or more than three phenolic hydroxyl groups include m-phenolphthalein, 4,6-dimethyl-2,4,6- tris(4-hydroxyphenyl)hept-2-ene, 4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptane, 1,3,5- tris(4-hydroxyphenyl)benzene, 1,1,1-tris(4-hydroxyphenyl)ethane, tris(4- hydroxyphenyl)phenylmethane, 2,2-bis[4,4-bis(4-hydroxyphenyl)cyclohexyl]propane, 2,4-bis(4- hydroxyphenylisopropyl)phenol, tetrakis(4-hydroxyphenyl)methane.

[0094] Some other trifunctional compounds are 2,4-dihydroxybenzoic acid, trimesic acid, cyanuric chloride and 3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

[0095] Preferred branching agents are 3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3- dihydroindole and 1,1,1-tris(4-hydroxyphenyl)ethane.

[0096] The amount of branching agent used, optionally, is from 0.05 to 2 mole %, still based on the number of moles of diphenol used in each case.

[0097] The branching agent can be prepositioned in the aqueous base phase together with the diphenol and the chain-stopper, or added in the form of a solution in an organic solvent prior to the phosgenation.

[0098] All these measures for the preparation of polycarbonates are familiar to the person skilled in the art.

[0099] Examples of aromatic dicarboxylic acids suitable for the preparation of polyester carbonates include phthalic acid, terephthalic acid, isophthalic acid, t-butyl isophthalic acid, 3,3'- diphenyl dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4-benzophenone dicarboxylic acid, 3,4'-benzophenone dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'- diphenyl sulfone dicarboxylic acid, 2,2-bis(4-carboxyphenyl)propane, trimethyl-3-phenyl indane- 4,5'-dicarboxylic acid.

[0100] Of the aromatic dicarboxylic acids, the use of terephthalic acid and / or isophthalic acid is particularly preferred.

[0101] Derivatives of the dicarboxylic acids are dicarbonyl dihalogen and dialkyl dicarboxylate, especially dicarbonyl dichloride and dimethyl dicarboxylate.

[0102] The replacement of the aromatic dicarboxylate groups by carbonate groups is essentially stoichiometric and also quantitative, so that the molar ratio of the reaction partners is also maintained in the final polyester carbonate. The aromatic dicarboxylate groups can be incorporated in a random as well as in a block form.

[0103] The polycarbonates used according to the application, including the preferred mode of preparation of polyester carbonates, are the known interfacial process and the known melt transesterification process (see, for example, WO 2004 / 063249 A1, WO 2001 / 05866 A1, US 5,340,905 A, US 5,097,002 A, US-A 5,717,057 A).

[0104] In the former case, the acid derivative used is preferably phosgene and optionally a dicarbonyl dichloride, in the latter case, preferably diphenyl carbonate and optionally a dicarboxylic acid diester. Catalysts, solvents, work-up, reaction conditions, etc. for the preparation of polycarbonates or polyester carbonates are well described and known in both cases.

[0105] It is also preferred to use copolycarbonates prepared from diphenols of the general formula (1 a):

[0106]

[0107] wherein

[0108] R 5 is hydrogen or Ci- to C4-alkyl, Ci- to C3-alkoxy, preferably hydrogen, methoxy or methyl,

[0109] R 6 , R 7 , R 8 and R 9 are each, independently of one another, Ci- to C4-alkyl or C6- to C 12 -aryl, preferably methyl or phenyl,

[0110] Y is a single bond, SO2-, -S-, -CO-, -O-, Ci- to C6-alkylene, C2- to C5-alkylidene, C6- to C 12 -arylene, or is C5- to C6-cycloalkylidene which can be mono- or poly-substituted by Ci- to C4-alkyl, preferably a single bond, -O-, isopropylidene or C5- to C6-cycloalkylidene which can be mono- or poly-substituted by Ci- to C4-alkyl,

[0111] V is oxygen, C2- to C6-alkylene or C3- to C6-alkylidene, preferably oxygen or C3-alkylene, p, q and r are each independently of the others 0 or 1,

[0112] W is a single bond when q = 0, and is oxygen, C2- to C6-alkylene or C3- to C6-alkylidene when q = 1 and r = 0, preferably oxygen or C3-alkylene,

[0113] W and V are each independently C2- to C6-alkylene or C3- to C6-alkylidene, preferably C3-alkylene, when q = 1 and r = 1,

[0114] Z is C1- to C6-alkylene, preferably C2-alkylene,

[0115] o is an average number of repeating units of 10 to 500, preferably 10 to 100, and

[0116] m is an average number of repeating units of 1 to 10, preferably 1 to 6, more preferably 1.5 to 5. It is likewise possible to use diphenols in which two or more siloxane blocks of general formula (1a) are connected to one another via terephthalic acid and / or isophthalic acid to form ester groups.

[0117] Especially preferred are (poly)siloxanes of formula (2) and (3)

[0118]

[0119] in which R1represents hydrogen, C1- to C4-alkyl, preferably hydrogen or methyl, especially preferably hydrogen,

[0120] each R2is independently of the others aryl or alkyl, preferably methyl,

[0121] X is a single bond, -SO2-, -CO-, -O-, -S-, C1- to C6-alkylene, C2- to C5-alkylidene or C6- to C 12 -arylene,

[0122] X is preferably a single bond, C1- to C5-alkylene, C2- to C5-alkylidene, C5- to C 12 -cycloalkylidene, -O-, -SO2-, -CO-, -S-, -SO2-, X is particularly preferably a single bond, isopropylidene, C5- to C 12 -cycloalkylidene or oxygen, very particularly preferably isopropylidene,

[0123] n is an average number of 10 to 400, preferably 10 to 100, especially preferably 15 to 50, and

[0124] m is an average number of 1 to 10, preferably 1 to 6, especially preferably 1.5 to 5.

[0125] The siloxane blocks can likewise preferably be derived from the following structures

[0126]

[0127] in which a in formulae (IV), (V) and (VI) is an average number of 10 to 400, preferably 10 to 100, particularly preferably 15 to 50.

[0128] It is likewise preferred here that at least two identical or different siloxane blocks of the general formula (IV), (V) or (VI) are connected to one another via terephthalic acid and / or isophthalic acid to form ester groups.

[0129] It is likewise preferred that, in formula (1a), p = 0, V is C3-alkylene, r = 1, Z is C2-alkylene, R 8 and R 9 is methyl, q = 1, W is C3-alkylene, m = 1, R 5 is hydrogen or C1- to C4-alkyl, preferably hydrogen or methyl, R 6 and R 7 are each, independently of one another, C1- to C4-alkyl, preferably methyl, and o is 10 to 500.

[0130] Copolycarbonates having monomer units of the formula (1a), in particular their preparation, are described in WO 2015 / 052106 A2.

[0131] Copolycarbonates having monomer units of the formula (IV), in particular their preparation, are described in WO 2015 / 052106 A2.

[0132] The compositions in the present application are "polycarbonate-based compositions". These are those compositions in which the base material, i.e. the component present predominantly, is a polycarbonate. "Predominantly" here means at least 44% by weight, preferably at least 50% by weight, more preferably at least 54% by weight, particularly preferably up to 60% by weight, of aromatic polycarbonate based on the total composition.

[0133] Component b

[0134] As component b of the thermoplastic composition which is the base layer of the multilayer structure, expanded graphite is used. The graphite used can be one type of expanded graphite, but it can also be a mixture of two or more types.

[0135] In expanded graphite, the individual basal planes of the graphite have been driven apart by a special treatment, thereby resulting in an increase in the graphite volume of preferably 200 to 400 times. The production of expanded graphite is described, inter alia, in the documents US 1,137,373 A, US 1,191,383 A and US 3,404,061 A.

[0136] Graphite is used in the composition in the form of fibres, rods, spheres, hollow spheres, flakes, in the form of a powder, in each case in agglomerated or agglomerated form, preferably in the form of flakes.

[0137] In the present application, structures in the form of platelets are understood to mean particles having a flat geometry. Thus, the height of the particles is generally significantly smaller than the width or length of the particles. Such flat particles can in turn be agglomerated or aggregated into structures.

[0138] The height of the primary particles in the form of platelets determined by atomic force microscopy, AFM, is less than 500 nm, preferably less than 200 nm, particularly preferably less than 100 nm. Due to the small size of these primary particles, the shape of the particles can be curved, curved, wavy or deformed in some other way.

[0139] The length dimension of the particles can be determined by standard methods, for example electron microscopy.

[0140] Graphite is used in the thermoplastic composition according to the application in an amount of 3.0 to 8.0% by weight, preferably 5.0 to 7.5% by weight, in order to achieve good thermal conductivity of the thermoplastic composition.

[0141] It is preferred according to the application to use graphite having a relatively high specific surface area, which is determined as BET surface area by means of nitrogen adsorption according to ASTM D3037:1993. It is preferred to use graphite having a BET surface area of > 5 m 2 / g, particularly preferably > 10 m 2 / g, very particularly preferably > 18 m 2 / g in the thermoplastic composition.

[0142] The graphite preferably has a particle size distribution determined by sieving according to DIN 51938:2015-09 characterized by a D(0.5) of at least 400 pm, more preferably at least 600 pm, still more preferably at least 650 pm to 1300 pm, particularly preferably at least 700 pm to 1200 pm, very particularly preferably 720 pm to < 1200 mm. In one embodiment, it is preferred that the particle size distribution has a D(0.5) of the expanded graphite of < 1000 pm.

[0143] Preferably, at least the range of D(0.5) applies to the graphite used. More preferably, in addition thereto, the following preferred ranges of D(0.1) and D(0.9) also apply - either alternatively or particularly preferably added together:

[0144] The graphite preferably has a particle size distribution determined by sieving according to DIN 51938:2015-09 characterized by a D(0.9) of at least 1 mm, preferably at least 1.2 mm, more preferably at least 1.4 mm, still more preferably at least 1.5 mm.

[0145] The graphite preferably also has a particle size distribution determined by sieving according to DIN 51938:2015-09 characterized by a D(0.1 ) of at least 100 pm, preferably at least 150 pm, more preferably at least 200 pm, yet more preferably at least 250 pm.

[0146] The graphite used preferably has a density determined with xylene of 2.0 g / cm3 3 to 2.4 g / cm3 3 , preferably 2.1 g / cm3 3 to 2.3 g / cm3 3 , more preferably 2.2 g / cm3 3 to 2.27 g / cm3 3 .

[0147] The carbon content of the graphite used in the layer structure according to the application is preferably > 90 %, more preferably > 95 %, yet more preferably > 98 %, determined according to DIN 51903:2012-11 at 800 °C for 20 hours.

[0148] The residual moisture content of the graphite used in the layer structure according to the application is preferably < 5 %, more preferably < 3 %, yet more preferably < 2 %, determined according to DIN 51904:2012-11 at 110 °C for 8 hours.

[0149] The graphite used in the layer structure according to the application has a thermal conductivity of 250 to 400 W / (m*K) parallel to the basal plane and 6 to 8 W / (m*K) perpendicular to the basal plane before processing.

[0150] The graphite used in the layer structure according to the application has an electrical resistivity of about 0.001 W*cm parallel to the basal plane and less than 0.1 W*cm perpendicular to the basal plane before processing.

[0151] The bulk density of the graphite determined according to DIN 51705:2001-06 is generally 50 g / l to 250 g / l, preferably 65 g / l to 220 g / l, more preferably 100 g / l to 200 g / l.

[0152] It is preferred to use graphite having a sulfur content of less than 200 ppm in the thermoplastic composition of the layer structure according to the application.

[0153] It is preferred to use graphite having an leachable chloride ion content of less than 100 ppm in the thermoplastic composition of the layer structure according to the application.

[0154] It is likewise preferred to use graphite having a nitrate and nitrite content of less than 50 ppm in the thermoplastic composition of the layer structure according to the application.

[0155] It is particularly preferred to use a graphite having all these limit values, i.e. limit values for the contents of sulfur, chloride, nitrate and nitrite.

[0156] Commercially available graphites are, inter alia, Ecophit GFG 5, Ecophit GFG 50, Ecophit GFG 200, Ecophit GFG 350, Ecophit GFG 500, Ecophit GFG 900, Ecophit GFG 1200 from the company SGL Carbon GmbH, TIMREX BNB90, TIMREX KS5-44, TIMREX KS6, TIMREX KS150, TIMREX SFG44, TIMREX SFG150, TIMREX C-THERM M 001 and TIMREX C-THERM TM 011 from Graphit Kropfmühl AG, Mechano-Cond 1, Mechano-Lube 2 and Mechano-Lube 4G from the company H.C. Carbon GmbH, Nord-Min 251 and Nord-Min 560T from the company Nordmann Rassmann GmbH and ASBURY A99, Asbury 230U and Asbury 3806 from the company Asbury Carbons.

[0157] Component c

[0158] The composition which can be used according to the application for the layer structure contains fused silica as component c. Fused silica, also called "fritted silica", is a quartz glass, fused and re-solidified silica. It can be a fused silica made from naturally occurring or synthetically produced quartz or made from a combination of both.

[0159] Component c is preferably a quartz material made from processed quartz sand by iron-free grinding and subsequent air classification.

[0160] Component c is contained in the composition in an amount of 34 to 38% by weight, preferably 35 to 37.5% by weight.

[0161] The silicon dioxide used in the composition for the base layer preferably has a particle shape which is spherical and / or near-spherical. Near-spherical here means the case where the axes of the spheroids, if the spheroids are described by isometric axes which run from a common origin and point into space, wherein these axes define the radius of the spheroids in all spatial directions, can deviate by at most 20% from the ideal of a sphere, so as to still comply with the near-spherical shape.

[0162] The fused silica is preferably characterized by a median diameter d(0.5) determined according to ISO 13320:2009-10 of 2 to 10 pm, more preferably 2.5 to 8.0 pm, still more preferably 3 to 5 pm, wherein it is preferred that the high value diameter d(0.9) determined according to ISO 13320:2009 is 6 to 34 pm, more preferably 6.5 to 25.0 pm, still more preferably 7 to 15 pm, particularly preferably 10 pm, respectively.

[0163] The fused silica preferably has a specific BET surface area determined by nitrogen adsorption according to ISO 9277:2010-09 of 0.4 to 8.0 m 2 / g, more preferably 2 to 7 m 2 / g, particularly preferably 4.4 to 6 m 2 / g.

[0164] The still more preferred fused silica has at most 3% by weight of secondary components, wherein it is preferred that the AI2O3 content is < 2.0% by weight, the Fe2O3 content is < 0.05% by weight, (CaO + MgO) < 0.1% by weight, (Na2O + K2O) < 0.1% by weight, in each case based on the total weight of the fused silica.

[0165] It is preferred to use a fused silica having a pH value in aqueous suspension determined according to ISO 10390:2005 of 6 to 9, more preferably 6.5 to 8.0.

[0166] The silicon dioxide preferably has an oil absorption number according to DIN EN ISO 787-5:1995-10 of preferably 20 to 30 g / 100 g.

[0167] It is possible to use a fused silica having a sizing on the surface, wherein it is preferred to use an epoxy-modified, polyurethane-modified and unmodified silane compound, a methylsilicone and a methacrylsilane sizing, or a mixture of the aforementioned silane compounds. It is particularly preferred to use an epoxy silane sizing. The sizing of the silicon dioxide is carried out by general methods known to the person skilled in the art.

[0168] However, the silicon dioxide used in the composition according to the application is preferably not sized.

[0169] It is recognized that the fused silica having the properties described as preferred can form component c alone or in admixture with one or more other fused silicas. Component c is preferably a fused silica having one or more of the properties described as preferred.

[0170] Component d

[0171] Furthermore, up to 10 wt.-%, preferably up to 6 wt.-%, more preferably up to 5 wt.-%, still more preferably 0.1 to 0.7 wt.-% of additional additives are optionally comprised, where these weight percentages, as here and elsewhere, are based on the total weight of the composition.

[0172] The group of additional additives does not include expanded graphite and does not include fused silica, as these have been described as components b and c.

[0173] Examples of such additives as are typically added to polycarbonate-containing compositions include heat stabilizers, antistatic agents, UV absorbers, IR absorbers, flame retardants, drip retardants, impact modifiers, antioxidants, inorganic pigments, carbon black, colorants and / or inorganic fillers such as titanium dioxide, silicates, aluminosilicates, talc, chalk, quartz powder, wollastonite, mica / clay layers, montmorillonite, aluminum oxide, magnesium oxide, (unfired) silica and / or barium sulfate and / or mold release agents in the amounts customary for polycarbonate, as described for example in EP 0 839 623 A1, WO 96 / 15102 A2, EP 0 500 496 A1 or in the "Plastics Additives Handbook", Hans Zweifel, 5thEdition 2000, Hanser Verlag, Mϋnchen. These additives can be added individually or as mixtures.

[0174] Suitable heat stabilizers are in particular phosphorus-based stabilizers selected from the group consisting of phosphates, phosphites, phosphonites, phosphines and mixtures thereof. Different compounds from one of these subgroups can also be used, for example a mixture of two phosphites.

[0175] The heat stabilizers preferably used are phosphorus compounds having oxidation number +III, in particular phosphines and / or phosphites.

[0176] Particularly preferred suitable heat stabilizers are triphenylphosphine, tris(2,4-di-tert- butylphenyl)phosphite (Irgafos 168), tetrakis(2,4-di-tert-butylphenyl)-bisphosphite- [1,1 -biphenyl]-4,4'-diyl bisphosphonate, octadecyl 3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate (Irganox 1076), bis(2,4-dicumylphenyl)pentaerythritol diphosphite (Doverphos S-9228), bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite (ADK STAB PE P-36).

[0177] They are used alone or in mixtures, for example Irganox B900 (a mixture of Irgafos 168 and Irganox 1076 in a ratio of 4:1) or Doverphos S-9228 with Irganox B900 or Irganox 1076.

[0178] The heat stabilizers are preferably used in amounts of up to 1.0 wt.-%, more preferably 0.003 to 1.0 wt.-%, still more preferably 0.005 to 0.5 wt.-%, particularly preferably 0.01 to 0.3 wt.-%.

[0179] Preferred release agents are esters of aliphatic long-chain carboxylic acids with mono- or polyhydric aliphatic and / or aromatic hydroxy compounds. Particularly preferred are pentaerythritol tetrastearate, glycerol monostearate, stearyl alcohol stearate and propylene glycol distearate or mixtures thereof.

[0180] Preferred UV absorbers have as low a transmittance as possible below 400 nm and as high a transmittance as possible above 400 nm. Particularly suitable UV absorbers for the compositions according to the application are benzotriazoles, triazines, benzophenones and / or arylated cyanoacrylates.

[0181] Particularly suitable UV absorbers are hydroxybenzotriazoles, such as 2-(3',5'-bis(1,1- dimethylbenzyl)-2'-hydroxyphenyl)benzotriazole (Tinuvin 234, Ciba Basel), 2-(2'-hydroxy-5'-(tert-octyl)phenyl)benzotriazole (Tinuvin 329, Ciba Basel), 2-(2'-hydroxy-3'-(2-butyl)-5'-(tert-butyl)phenyl)benzotriazole (Tinuvin 350, Ciba Basel), bis(3-(2H-benzotriazyl)-2-hydroxy-5-tert-octyl)methane (Chimassorb 81 1, 360, Ciba Basel), (2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyloxy)phenol (Tinuvin 1577, Ciba Basel), and benzophenone 2,4-dihydroxybenzophenone (Chimasorb 22, Ciba Basel) and 2-hydroxy-4-(octyloxy)benzophenone (Chimassorb 81, Ciba, Basel), 2- cyano-3,3-diphenyl-2-propenoic acid 2-ethylhexyl ester, 2,2-bis[[2-cyano-1 -oxo-3,3- diphenyl-2-propenyl)oxy]methyl]-1,3-propanediyl ester (9CI) (Uvinul 3030, BASF AG Ludwigshafen), 2-[2-hydroxy-4-(2-ethylhexyl)oxy]phenyl-4,6-bis(4- phenyl)phenyl-1,3,5-triazine (CGXUVA 006, Ciba Spezialitatenchemie, Basel) or 2,2'-(1,4- phenylenedimethylene) bispropanedioic acid tetraethyl ester (Hostavin B-Cap, Clariant AG).

[0182] Particularly preferred specific UV stabilizers are, for example, Tinuvin 360, Tinuvin 350, Tinuvin 329, Hostavin B-CAP, more preferably TIN 329 and Hostavin B-Cap. Mixtures of these UV absorbers can also be used. Particularly suitable UV absorbers are hydroxybenzotriazoles, such as 2-(3',5'-bis(1,1 -dimethylbenzyl)-2'- hydroxyphenyl)benzotriazole (Tinuvin 234, BASF SE, Ludwigshafen), 2-(2'-hydroxy-5'-(tert- octyl)phenyl)benzotriazole (Tinuvin 329, BASF SE, Ludwigshafen), bis(3-(2H-benzotriazolyl)-2- hydroxy-5-tert-octyl)methane (Tinuvin 360, BASF SE, Ludwigshafen), 2-(4,6-diphenyl-1,3,5- triazin-2-yl)-5-(hexyloxy)phenol (Tinuvin 1577, BASF SE, Ludwigshafen), 2-(5-chloro-2H- benzotriazol-2-yl)-6-(1,1 -dimethylethyl)-4-methylphenol (Tinuvin 326, BASF SE, Ludwigshafen), and benzophenones, such as 2,4-dihydroxybenzophenone (Chimassorb 22, BASF SE, Ludwigshafen) and 2-hydroxy-4-(octyloxy)benzophenone (Chimassorb 81, BASF SE, Ludwigshafen), 2,2-bis[[2-cyano-1 -oxo-3,3-diphenyl-2-propenyl)oxy]methyl]-1,3- propanediyl ester (9CI) (Uvinul 3030, BASF SE Ludwigshafen), 2-[2-hydroxy-4-(2- ethylhexyl)oxy]phenyl-4,6-bis(4-phenyl)phenyl-1,3,5-triazine (Tinuvin 1600, BASF SE, Ludwigshafen), 2,2'-(1,4-phenylenedimethylene)bispropanediol tetraethyl ester (Hostavin B-Cap, Clariant AG) or N-(2-ethoxyphenyl)-N'-(2-ethylphenyl)oxalamide (Tinuvin 312, CAS No. 23949-66-8, BASF SE, Ludwigshafen).

[0183] Particularly preferred specific UV stabilizers are Tinuvin 360, Tinuvin 329, Tinuvin 326, Tinuvin 1600, Tinuvin 312, Uvinul 3030 and / or Hostavin B-Cap, very particularly preferred are Tinuvin 329 and Tinuvin 360.

[0184] If an ultraviolet absorber is present, the composition preferably contains the ultraviolet absorber in an amount of up to 0.8% by weight, preferably 0.05% to 0.5% by weight, more preferably 0.08% to 0.4% by weight, very particularly preferably 0.1% to 0.35% by weight, based on the total composition.

[0185] Suitable infrared absorbers are disclosed, for example, in EP 1 559 743 A1, EP 1 865 027 A1, DE 100 22 037 A1, DE 100 06 208 A1 and in the Italian patent applications RM2010A000225, RM2010A000227 and RM2010A000228. Of the infrared absorbers mentioned in the cited documents, preference is given to those based on borides and tungstates, in particular cesium tungstate or zinc-doped cesium tungstate, and ITO- and ATO-based absorbers and combinations thereof.

[0186] The composition according to the application can also contain a phosphoric acid ester or a sulfonic acid ester as transesterification stabilizer. It is preferred to include triisooctyl phosphate as transesterification stabilizer. Triisooctyl phosphate is preferably used in an amount of 0.003% to 0.05% by weight, more preferably 0.005% to 0.04% by weight, particularly preferably 0.01% to 0.03% by weight, based on the total composition.

[0187] Suitable colorants can be pigments, organic and inorganic pigments, carbon black and / or dyes. The colorants or pigments in the present application are sulfur-containing pigments, such as cadmium red or cadmium yellow, iron cyanide-based pigments such as Prussian blue, oxide pigments such as zinc oxide, red iron oxide, black iron oxide, chromium oxide, titanium yellow, zinc / iron-based brown, titanium / cobalt-based green, cobalt blue, copper / chromium-based black and copper / iron-based black, or chromium-based pigments such as chromium yellow, phthalocyanine-derived dyes such as copper phthalocyanine blue or copper phthalocyanine green, condensed polycyclic dyes and pigments such as azo-based (e.g. nickel azo yellow), sulfur indigo dyes, Perinon-based, perylene-based, quinacridone-derived, dioxazine-based, isoindolinone-based and quinophthalone-derived derivatives, anthraquinone-based heterocyclic systems.

[0188] Specific examples of commercial products are, for example, MACROLEX Blue RR, MACROLEX Violet 3R, MACROLEX Violet B (Lanxess AG, Germany), Sumiplast Violet RR, Sumiplast Violet B, Sumiplast Blue OR (Sumitomo Chemical Co., Ltd.), Diaresin Violet D, Diaresin Blue G, Diaresin Blue N (Mitsubishi Chemical Corporation), Heliogen Blue or Heliogen Green (BASF AG, Germany). Preferred among these are cyanine derivatives, quinoline derivatives, anthraquinone derivatives, phthalocyanine derivatives.

[0189] It is likewise possible to add fillers which are different from components b and c, provided that their type and amount do not adversely impair the performance level of the application. These can have, for example, particulate, flaky or fibrous properties. Examples which can be mentioned in this connection include chalk, barium sulfate, silicates / aluminosilicates, for example mica / clay lamellar minerals, montmorillonite, especially also organophilic forms modified by ion exchange, kaolin, zeolite, vermiculite, magnesium hydroxide and aluminum hydroxide. It is also possible to use mixtures of different inorganic materials.

[0190] The composition is preferably free of waxy stabilizers.

[0191] The additional additives are preferably only one or more selected from the group consisting of heat stabilizers, antistatic agents, ultraviolet absorbers, infrared absorbers, antioxidants, inorganic pigments, carbon black, colorants, silicates, especially aluminosilicates, chalk, quartz powder, mica / clay lamellae, montmorillonite, aluminum oxide, magnesium oxide, (unfired) silicon dioxide, barium sulfate and / or release agents.

[0192] It is furthermore possible to add further ingredients which, depending on their type and amount, do not adversely impair the performance level of the application.

[0193] It is to be appreciated that the thermoplastic composition of the substrate layer can in principle also contain, for example, a blending partner. Examples of thermoplastic polymers which are suitable as blending partners are polystyrene, styrene copolymers, aromatic polyesters such as polyethylene terephthalate (PET), PET-cyclohexane dimethanol copolymer (PETG), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), cyclic polyolefins, poly- or copoly-acrylates, poly- or copoly-methacrylates, for example poly- or copoly-methyl methacrylate (such as PMMA), and copolymers with styrene, for example transparent polystyrene-acrylonitrile (PSAN), thermoplastic polyurethanes and / or polymers based on cyclic olefins (for example TOPAS, a commercial product from Ticona).

[0194] It is particularly preferred for the composition for the base layer according to the application to contain at least one heat stabilizer, a mold release agent and carbon black as additives. Apart from components a, b and c and in each case one or more heat stabilizers, mold release agents and carbon black, it is very particularly preferred not to contain further components.

[0195] For the base layer, the longitudinal and transverse CLTE values determined according to DIN 53752 - Method A: 1980 are preferably values of < 46.5 ppm / K, wherein the ratio thereof (longitudinal / transverse) is more preferably > 0.84, and / or

[0196] The in-plane thermal conductivity of the base layer determined according to ASTM E 1461 :2013 is preferably > 0.7 W / (m-K), more preferably > 0.85 W / (m-K), particularly preferably > 0.89 W / (m-K), and / or

[0197] The through-plane thermal conductivity of the base layer determined according to ASTM E 1461 :2013 is preferably > 0.45 W / (m-K).

[0198] The gloss determined according to ASTM D 523-14 of the base layer is preferably > 90°, more preferably > 92°, still more preferably > 94°.

[0199] Still more preferably, the Vicat temperature of the composition of the base layer determined according to DIN ISO 306:2014-3 is additionally > 141 °C, particularly preferably > 142 °C.

[0200] Due to the requirements set, it is particularly preferred for all these properties to be met together.

[0201] The composition of the base layer according to the application containing components a to c and optionally d and optionally a blending partner is produced by standard incorporation processes by combining, mixing and homogenizing the individual components, wherein in particular the homogenization is carried out in the melt under the action of shear forces. The combining and mixing can optionally be carried out using a powder premix before melt homogenization.

[0202] It is also possible to use a pellet premix having components b, c and optionally d, or a premix of pellets and powder.

[0203] It is also possible to use a premix made from a solution of the mixture components in a suitable solvent, wherein optional homogenization in the solution and subsequent removal of the solvent takes place.

[0204] In particular, components b, c and optionally d of the composition according to the application can be introduced into the polycarbonate here, optionally together with a blending partner, by known methods or in the form of a masterbatch.

[0205] It is preferred to use a masterbatch for the individual or mixed introduction of components b, c and optionally d.

[0206] In this regard, the composition according to the application can be combined, mixed, homogenized and subsequently extruded in a conventional device, such as a screw extruder (e.g. twin-screw extruder, ZSK), a kneader or a Brabender or Banbury mill. After extrusion, the extrudate can be cooled and comminuted. It is also possible to premix the individual components, which can then be added to the remaining raw materials separately and / or likewise mixed.

[0207] The combination and mixing of the premix in the melt can also be carried out in the plasticating unit of an injection molding machine. In this case, the melt is directly converted into a molded part in a subsequent step.

[0208] The composition according to the application can be processed in a conventional manner in conventional machines, for example in an extruder or an injection molding machine, to produce any molded part. Dynamic mold temperature control is used in the injection molding process when producing the base layer of the layer structure according to the application. The conditions used therefor are generally determined by the machine operator in accordance with their expert knowledge. In the dynamic mold temperature control for producing the base layer of the layer structure according to the application, a material temperature of 300 to 340°C, a mold temperature of 140 to 170°C, an injection speed of 40 to 80 mm / s and a holding pressure of 700 to 900 bar are generally selected conditions; for example, a material temperature of 330°C, a mold temperature of 160°C, an injection speed of 40 mm / s and a holding pressure of 900 bar. Examples

[0209] 1. Description of raw materials and test methods

[0210] The polycarbonate compositions described in the following examples were produced by compounding on a MX58 co-kneader from the company BUSS at a throughput of 80 kg / h. The melt temperature was 250 to 310°C, wherein the kneader housing, the kneader shaft and the discharge housing and the shaft of the discharge screw had a defined temperature of 260°C. The temperature of the nozzle plate was 300°C. Component b was added via a side extruder together with the powder premix (polycarbonate powder + additives), component c was added directly via the main inlet.

[0211] Component a: linear polycarbonate based on bisphenol A having a melt volume flow rate MVR (according to ISO 1133:2012-03 at a test temperature of 300°C and a load of 1.2 kg) of 19 cm3 / (10 min). 3 Component a: linear polycarbonate based on bisphenol A having a melt volume flow rate MVR (according to ISO 1133:2012-03 at a test temperature of 300°C and a load of 1.2 kg) of 19 cm3 / (10 min).

[0212] Component b-1 : expanded graphite: GFG 900 from the company SGL Carbon GmbH having a D(0.5) according to DIN 51938:2015-09 of approximately 900 pm. Component b-1 : expanded graphite: GFG 900 from the company SGL Carbon GmbH having a D(0.5) according to DIN 51938:2015-09 of approximately 900 pm.

[0213] Component b-2: expanded graphite: SC 4000 O / SM from Graphit Kropfmühl GmbH, having a D(0.5) according to DIN 51938:2015-09 of about 1000 pm.

[0214] Component c: fused silica: Amosil FW 600 from Quarzwerke GmbH, Frechen, ungelled, having a median particle size D(0.5) of about 4 pm, a D(0.98) of about 13 pm, a D(0.1) / D(0.9) ratio of about 1.5 / 10 and a specific surface area of about 6 m 2 / g, determined according to DIN-ISO 9277:2014-01.

[0215] Component c*: compacted talc, having a talc content of 98 wt.-%, an iron oxide content of 1.9 wt.-%, an aluminum oxide content of 0.2 wt.-%, a loss on ignition (DIN 51081 / 1000 °C) of 5.4 wt.-%, a pH value of 9.15 (according to EN ISO 787-9:1995), a D(0.5) (sedimentation analysis) of 2.2 pm; a BET surface area according to ISO 4652:2012-06 of 10 m 2 / g, type: Finntalc M05SLC, manufacturer: Mondo Minerals B.V.

[0216] Component d-1 : “wax”. Maleic anhydride modified polypropylene copolymer (AC907P) from Honeywell, having an average molecular weight (gel permeation chromatography in o-dichlorobenzene at 150 °C under polystyrene calibration) M w = 20700 g / mol, M n = 1460 g / mol and having an acid value (ASTM D-1386:2015) of 78 mg KOH / g.

[0217] The Vicat softening temperature VST / B50 or B120 as a measure of the resistance to heat distortion was determined according to DIN ISO 306:2014-3 on specimens of size 8 mm x 10 mm x 4 mm with a piston load of 50 N and a heating rate of 50 °C / h or 120 °C / h using a Coesfeld Eco 2920 instrument from Coesfeld Materialtest GmbH.

[0218] The coefficient of thermal expansion (CLTE) was measured according to DIN 53752:1980-12 (linear thermal expansion coefficient, parallel / vertical, at 23-60 °C (with a heating rate of 3 K / min).

[0219] The thermal conductivity TCin the injection molding direction (in-plane) at 23 °C was determined on specimens of size 60 mm x 60 mm x 2 mm according to ASTM E 1461 :2013.

[0220] The thermal conductivity TCin the injection molding direction (through-plane) at 23 °C was determined on specimens of size 60 mm x 60 mm x 2 mm according to ASTM E 1461 :2013.

[0221] The melt viscosity was determined according to ISO 11443:2014-04 with a Visco-Robo 45.00 instrument (cone / plate arrangement) from

[0222] The density was determined according to ISO 1183-1 :2012.

[0223] The glossiness was determined according to ASTM D 523-14.

[0224] The specimens for the determination of the surface quality were produced by injection molding with dynamic mold temperature control. Here, the material was processed at a material temperature of 330 °C and a mold temperature of 166 °C (heating) and 85 °C (cooling). The injection speed was 40 mm / s and the holding pressure was 900 bar.

[0225] After the test, the metal layer was applied to the base layer by the following method:

[0226] The coating apparatus consists of a vacuum chamber, in which the specimens are placed on a rotating specimen holder. The specimen holder is rotated at approximately 20 revolutions per minute. Before they are introduced into the vacuum chamber, the specimens are blown with ionized air to clean them of dust. For metallization, argon is introduced at a pressure of 5 · 10 -3 millibar. Using a direct current magnetron, an aluminum layer of approximately 200 nm thickness is applied to the specimens at a power density of 6.4 W / cm 2

[0227]

[0228] ​​The thermal conductivity of the composition is determined by the introduced filler and its proportion by weight or volume. The specific thermal conductivity of the filler decisively determines the degree of thermal conductivity of the overall composition. The use of a poor thermal conductor (e.g. quartz) leads to a total thermal conductivity (in-plane) of 0.32 W / mK at a concentration of 40 wt% (V1), which is too low to achieve the desired purpose. A major advantage of quartz as a spherical filler is the high dimensional stability of the composition (expressed by the ratio of parallel / vertical CLTE, here 0.98). The addition of graphite or partial replacement of the filler with graphite enables an increase in thermal conductivity; however, due to its flake-like particle geometry, the dimensional stability of the overall composition decreases. At low concentrations of graphite (V2 and V3), although the CLTE ratio (and thus the degree of isotropy) remains very close to the ideal value (CLTE 平行 = CLTE 垂直 = 1.0) at all times, the thermal conductivity increases only minimally, even at a total filler content of 45%. The addition of 5-7.5 wt% graphite (E1-E3) provides the best balance between in-plane thermal conductivity (> 0.85 W / mK) and isotropy (≥ 0.84).

[0229] The choice of graphite also influences these properties due to the particle size distribution. For example, for graphite b2, a lower thermal conductivity is achieved at least at low concentrations (see E4 and E1). Although the compositions E3 and V5 have the same CLTE quotient, the higher filler content (45%) in E3 is preferred because it leads to a lower CLTE and thus to a smaller shrinkage behavior.

[0230] Another disadvantage of high graphite amounts is the surface quality (measured using gloss). This is evident in V4 and V5, whose gloss is far lower than that of the other compositions containing less graphite. Although the combination of graphite and talc as fillers (V6 and V7) has already led to a high thermal conductivity even at a lower total filler content, there is the major disadvantage of a decrease in dimensional stability (see CLTE quotient) due to the flake-like particle geometry as in the case of graphite. Furthermore, talc can only be incorporated into polycarbonate with the aid of a waxy stabilizer (d). However, this stabilizer leads to the formation of streaks on the surface during processing, which has a negative effect on the metal adhesion and the thermal stability of the reflector structure.

[0231] As can be seen on the basis of the examples shown, only the balanced ratio of quartz and graphite (E1-E3, E4) leads to a good combination of properties of CLTE, CLTE quotient, thermal conductivity and surface quality (gloss).

Claims

1. Layered structure, which includes i) A base layer made of a thermoplastic polycarbonate-based composition, and ii) A metal layer applied to substrate i, Its features The thermoplastic polycarbonate-based composition of the base layer i contains the following components: a) 44% to 63% by weight of aromatic polycarbonate, b) 3% to 8% by weight of expanded graphite c) 34% to 38% by weight of molten silica, d) One or more additional additives, ranging from 0% to 10% by weight. The total amount of expanded graphite and molten silica is at least 40% by weight.

2. The layer structure as described in claim 1, wherein the thermoplastic polycarbonate-based composition of the base layer i contains a) 54% to 60% by weight of aromatic polycarbonate, b) 5% to 7.5% by weight of expanded graphite, c) 35% to 37.5% by weight of molten silica, d) One or more additional additives, ranging from 0% to 5% by weight.

3. The layer structure as described in claim 1 or 2, wherein the base layer is formed by injection molding under dynamic mold temperature control.

4. The layer structure as described in claim 1 or 2, wherein the layer structure does not include any layers other than one or more optional protective layers.

5. The layer structure as described in claim 1 or 2, wherein the thermoplastic polycarbonate-based composition of the base layer i is composed of components a to c and optionally d.

6. The layer structure as described in claim 1 or 2, wherein the additional additives are selected from flame retardants, heat stabilizers, antistatic agents, ultraviolet absorbers, infrared absorbers, anti-drip agents, impact modifiers, antioxidants, inorganic pigments, organic colorants, inorganic fillers and / or release agents.

7. The layer structure as described in claim 1 or 2, wherein the additional additive is selected from carbon black.

8. The layer structure as described in claim 1 or 2, wherein the D(0.5) of the expanded graphite, as determined by sieve analysis according to DIN 51938:2015-09, is from 700 µm to 1200 µm.

9. The layer structure as described in claim 1 or 2, wherein the D(0.5) of the molten silica, as determined according to ISO 13320:2009-10, is from 2.5 µm to 8.0 µm.

10. The layer structure as described in claim 1 or 2, wherein the D(0.5) of the molten silica, as determined according to ISO 13320:2009-10, is 3 µm to 5 µm.

11. The layer structure as described in claim 1 or 2, wherein for the base layer, the longitudinal:transverse ratio of the longitudinal and transverse CLTE values, as determined according to DIN 53752-Method A:1980, is ≥ 0.84, the in-plane thermal conductivity, as determined according to ASTM E 1461:2013, is ≥ 0.7 W / (m·K), the Vicat temperature, as determined according to DIN ISO 306:2014-3, is ≥ 141°C, and the gloss, as determined according to ASTM D 523-14, is > 90°.

12. The layer structure as described in claim 1 or 2, wherein the metal layer ii has a thickness of ≥ 60 nm to ≤ 300 nm as determined by atomic force microscopy.

13. A component comprising a layered structure as described in any of the preceding claims.

14. The component of claim 13, wherein the component is a reflector or a mirror element of a head-up display.

15. The component of claim 14, wherein the component is a headlight reflector.

16. A method for producing the layered structure as described in any one of claims 1 to 12, wherein a) A base layer is formed from a thermoplastic polycarbonate-based composition by single-component injection molding under dynamic mold temperature control, and then... b) Apply a metal layer to this substrate layer.

Images