WO2022180221A1

WO2022180221A1 - Polymers having improved thermal conductivity

Info

Publication number: WO2022180221A1
Application number: PCT/EP2022/054812
Authority: WO
Inventors: Roland Helmut Krämer; Rui DOU; Li Rong HE; Aron WOSYLUS
Original assignee: Basf Se
Priority date: 2021-02-25
Filing date: 2022-02-25
Publication date: 2022-09-01

Abstract

The use of aluminium particles having an average particle size of from 1 to 150 μm which are surface-coated with an SiO₂ layer having a layer thickness of 1 to 200 nm as thermally conductive filler in organic polymers or precursors of organic polymers.

Description

Polymers having improved thermal conductivity

Description

The present invention relates to the use of specific thermally conductive fillers in organic poly mers or precursors of organic polymers, to thermoplastic molding compositions or polyol com positions comprising the thermally conductive filler, processes for preparing them, their use and moldings made thereof.

In general, the present invention relates to heat dissipating polymer composites and in particular to thermally conductive polymer composites which incorporate an effective thermally conductive filler.

Heat dissipation is of great importance to the life span of high-performance electrical and elec tric devices. Therefore, it is crucial that the heat generated from these devices is dissipated as quickly and as effectively as possible, thereby maintaining the operating temperature and per formance of the device.

Conventionally, metal is used to produce heat dissipation articles, such as an LED heat sink or motor bobbin, mainly due to the high thermal conductivity of the metal. However, the manufac turing process from raw materials to final product is typically long and complicated. Moreover, an electrical insolation is often necessary, involving surface coatings or added spacers, when the electrical insulative property is essential for the application of the electrical device.

On the other hand, polymer composites benefit from low processing costs, low density and a wide range of designed flexibility. However, the thermal conductivity of polymers is low.

The thermal conductivity of polymers can be enhanced by the addition of thermally conductive fillers, including electrically conductive fillers, such as graphite, carbon fibers, carbon black, or metal particles, and electrically insulating fillers like hexagonal boron nitride (h-BN), ceramic or mineral particles.

If a high thermal conductivity with electrical insulation in a polymer composite material is re quired, usually hexagonal boron nitride is employed.

Thermoplastic molding compositions containing thermally conductive fillers for improving the thermal conductivity are known.

US 2017/0355894 A1 discloses thermally conductive composites and methods for preparing them. The matrix polymer is mixed with a high-aspect ratio thermally conductive filler which can be se lected from boron nitride flakes, graphite flakes, expandable graphite, carbon fiber, graphene, molybdenum disulphide whiskers, magnesium oxide whiskers, aluminium oxide whiskers, cal cium sulfate whiskers, silicon carbide whiskers, metal fibers, metal flakes or combinations thereof. For example, high-density polyethylene is mixed with silicon carbide particles and graphite flakes. Furthermore, polyamides like PA 66 can be mixed with MgO particles and boron nitride flakes.

CN 107573904 discloses a composite thermal conductive material which includes a sheet shaped additive. For example, flake additives are employed, including alumina, aluminium ni tride, boron nitride, zinc oxide, silver, aluminium, copper and zinc as well as graphite micro plates or graphene microplatelets. It is disclosed that flake additives can serve as a thermal conduction bridge between particulate additives. The main material can include silicone grease, polyphenylene sulfide resin, polypropylene and polystyrene.

EP 2 935464 B1 discloses polymer composite components for wireless-communication towers. The polymer composites can be based on thermoplastic polymers including among others poly amides. Fillers that have a high thermal conductivity are quartz, fused silica / quartz, aluminium flakes, magnesium powder, carbon fiber, graphite, graphene and expanded graphite.

Polym. Adv. Technol. 2015, 26, pages 362 to 368 refers to the effect of conductive particles on the mechanical, electrical, and thermal properties of maleated polyethylene. The effects of iron and aluminium conductive particles are studied. Increase in particle concentration was shown to improve the tensile strength and modulus of the matrix. Inclusion of the particles led to a sub stantial increase in the thermal conductivity of the composites. Maleic anhydride grafted poly ethylene was filled with aluminium powder having a particle size of less than 150 pm. The alu minium particles had an elongated shape and were oriented in the direction of squeezing flow.

Advanced Materials Research, Vols. 194-196, pages 1680 to 1684 refers to the thermal proper ties of aluminium particle reinforced silicon rubber composites. Micro-sized aluminium reinforced silicone rubber composites were prepared, wherein surface-passivated composite Al particles are employed. The surface modification of the Al particles was performed by functionalization of the surface with an aminopropyltriethoxysilane coupling agent. The aluminium particles can be aluminium flakes or spherical particles. It is disclosed that the use of silane coupler enhanced the interfacial bonding and reduced the voids between the Al particles and rubber so that the surface treatment of Al with silane increased the thermal conductivity.

Journal of Applied Polymer Science, Vol. 118, pages 3156 to 3166 (2010) refers to the thermal and dielectric properties of the aluminium particle/epoxy resin composites. It is disclosed that the introduction of aluminium particles to the composites hardly influenced the thermal stability behaviour, and decreased the glass transition temperature of the epoxy resin. The size, concen tration and surface modification of aluminium particles had an effect on their thermal conductiv ity and dielectric properties. The surface modification of the aluminium particles was affected by surface treatment with glycidoxypropyltrimethoxysilane. It is stated that the use of a coupling agent improved the thermal conductivity.

The inclusion of aluminium particles in organic polymers may lead to safety hazards since in hu mid environment, the aluminium particles having a high surface area can corrode and release hydrogen. Specifically under acidic conditions, organic polymers containing aluminium particles may not be stable.

The object underlying the present invention is to provide aluminium particles that can be em ployed as thermally conductive fillers in organic polymers or precursors of organic polymers that overcome the disadvantages of the known fillers and preferably are inert or corrosion resistant under humid or acidic environments.

Furthermore, an aluminium filler for organic polymers or precursors of organic polymers shall be provided which has an increased thermal conductivity in the polymer.

A further object is to provide electrically insulating fillers which also combine excellent disper sion in a polymer matrix, better acid corrosion than traditional pure aluminium, and that prefera bly enable a versatile surface functionalization.

The objects are achieved according to the present invention by the use of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thickness of 1 to 200 nm as thermally conductive filler in organic polymers or pre cursors of organic polymers.

Furthermore, the objects are achieved by a method for increasing the chemical stability of or ganic polymers or precursors of organic polymers filled with aluminium particles, involving the step of adding aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thickness of 1 to 200 nm to the organic pol ymers or precursors of organic polymers.

Furthermore, the objects are achieved by a thermoplastic molding composition comprising a) from 5 to 99% by weight of at least one thermoplastic polymer as component A, b) from 1 to 90% by weight of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thickness of 1 to 200 nm as component B, c) from 0 to 60% by weight of at least one fibrous or particulate filler which is different from component B, as component C, d) from 0 to 50% by weight of further additives, as component D, where the total of the percentages by weight of components A to D is 100% by weight.

Furthermore, the objects are achieved by a polyol composition for producing polyurethanes, comprising a’) from 5 to 99% by weight of at least one polyol, as component A’, b’) from 1 to 90% by weight of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thickness of 1 to 200 nm, as component B’, c’) from 0 to 30% by weight of further additives, as component C’, where the total of the percentages by weight of components A’ to C’ is 100% by weight.

The object is furthermore achieved by a process for preparing the thermoplastic molding com position or polyol composition by mixing the ingredients.

The objects are furthermore achieved by the use of the thermoplastic molding composition or polyol composition for forming moldings, and a respective molding made of a thermoplastic molding composition or a polyurethane reactive system comprising the polyol composition and an isocyanate component.

According to the present invention it has been found that the surface coating of aluminium parti cles with an S1O2 layer having a layer thickness of 1 to 200 nm leads to aluminium particles that withstand corrosion or reaction with water or acids in humid or acidic environments.

Furthermore, it has been found according to the present invention that these coated aluminium particles have an increased thermal conductivity when added to organic polymers.

The S1O2 coating on the aluminium particles has a dual function: The coating makes the alumin ium particles inert (chemicals resistant) or corrosion resistant due to a passivation. The typical passivation of aluminium particles by an alumina surface layer is typically not sufficient to allow for a satisfactory corrosion inhibition or prevention of a reactivity with water or acids.

Furthermore, the surface coating with an S1O2 layer allows for a better dispersion of the alumin ium particles, preferably sheets or flakes, within the organic polymer, leading to a better thermal conductivity.

On the other hand, the electrical conductivity is lowered by the S1O2 layer.

The aluminium particles have an average particle size of from 1 to 150 pm, preferably 5 to 100 pm, more preferably 10 to 50 pm, most preferably 15 to 40 pm. For example, the average particle size can be in the range of from 20 to 30 pm. The average particle size refers to the number average or arithmetical average. It can be determined by measuring the longest dimen sion of a number of particles and calculating the number average value therefrom.

The particle size can be determined by measuring the size of a certain number of particles by hand or by employing suitable analytic tools, e.g. a camsizer. Typically, at least 100 discrete particles are measured in order to obtain the dso value. The average particle size (dso) is prefer ably the arithmetic or number mean diameter (d). Preferably, particle sizes are determined by static laser diffraction using a Mastersizer 2000 (Malvern Instruments Ltd) after dilution of the sample with isopropanol in order to obtain an opti cal concentration suitable for the measurement. For the dispersion of the sample a dispersing module Hydro SM was used with a stirrer speed of 2500 rpm. The calculation of the particle size distribution may be performed by the Mastersizer 2000 using Fraunhofer theory.

The aluminium particles can have any desired form. They can be spherical, ellipsoidal, granular or in the form of sheets or flakes. In sheets or flakes, the average particle size refers to the long est size within the particles.

Preferably, the aluminium particles are sheets or flakes as described below. The thickness is the smallest dimension of the particles. An average particle thickness can be determined in the same way as the average particle size. The numbers below can refer to the average particle thickness or absolute particle thickness.

Preferably, the aluminium particles have an aspect ratio of from 2 to 750, preferably 5 to 500, more preferably 10 to 500, more preferably 20 to 250.

Preferably, aluminium sheets or flakes have a thickness of from 100 to 1000nm, more prefera bly of from 200nm to 500nm, most preferably 200nm to 400nm. The thickness of the aluminium sheets or flakes is preferably 0.1 to 50 % or 0.2 to 50% of the average particle size, more pref erably 0.2 to 20 %, even more preferably 0.3 to 10 %, most preferably 0.4 to 5 % of the average particle size.

Suitable aluminium particles can be obtained from DIC, ECKART, Nanoshel etc.

The aluminium flakes or sheets can lead to preferable thermal conductivities in organic poly mers.

The SiC>2 coating acts as a passivation layer which enables good dispersion, good electrical in sulation, combined with good chemical stability or corrosion stability against humidity and acids. Furthermore, S1O2 layers allow for a sizing to improve the adhesion with a polymer matrix.

According to one embodiment of the present invention, the surface coated aluminium particles are furthermore surface-functionalized with a silane coupling agent. Suitable silane coupling agents are discussed below in connection with glass fibers. These silane coupling agents can be employed to further functionalize the aluminium particles as employed according to the pre sent invention. The passivation layer of silica therefore has a triple effect: good dispersion of the aluminium particles in a polymer matrix, leading to an improved thermal conductivity action as a barrier for water and acid, hindering the corrosion and generation of hydrogen in humid and acidic environments the silica layer allows for a versatile surface functionalization with silane coupling agents.

The SiC>2 layer surface coating preferably has a thickness of from 2 to 100 nm, more preferably 5 to 50 nm, specifically 7 to 40 nm.

The surface coated particles preferably have the above-mentioned average particle size com bined with an average thickness of from 102 to 1100nm, more preferably of from 205 to 550nm, most preferably 207 to 540nm.

The surface coating with S1O2 is preferably performed in following manner:

The S1O2 coated aluminum composite particles were prepared by hydrolysis-condensation polymerization of tetraethyl orthosilicate (TEOS) on the surface of aluminum particles. The alu minum particle was dispersed into the mixture of TEOS and 200 ml. ethanol with the mole ratio of TEOS to Al of 1 :50, then 10 ml NH40H was added slowly, and the mixture was vigorously stirred at 40 °C for 6 h. After the reaction, the silica coated aluminum particle was collected by centrifuge and washed with ethanol followed by deionized water for several times to remove dis sociative polysiloxane, unreacted monomer, and polysiloxane oligomers. The composite parti cles were then dried at 40°C in vacuum oven.

Reference is made to “Zhi Peng Cheng etc. Synthesis and characterization of aluminum parti cles coated with uniform silica shell. Transactions of Nonferrous Metals Society of China. Vol ume 18, Issue 2, April 2008, Pages 378-382.”

The S1O2 coating enhances the resistance to chemicals or the inertness of the aluminium parti cles towards chemicals. The coating therefore increases the chemical stability of the aluminium particles.

The aluminium particles can be added to any desired organic polymer or precursor of organic polymers. Precursors of organic polymers can be prepolymers or monomers that form the re spective polymer. For a polyurethane, for example, the aluminium particles can be added to the polyol component or hydroxy-functionalized component that is reacted with an isocyanate com ponent like a polyisocyanate.

The amount of aluminium particles added to the organic polymer can be very high. The alumin ium particles can make up to 90% by weight, preferably up to 80% by weight, preferably up to 70% by weight of the polymer composition. The invention also relates to a thermoplastic molding composition comprising a) from 5 to 99% by weight of at least one thermoplastic polymer as component A, b) from 1 to 90% by weight of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thickness of 1 to 200 nm as component B, c) from 0 to 60% by weight of at least one fibrous or particulate filler which is different from component B, as component C, d) from 0 to 50% by weight of further additives, as component D, where the total of the percentages by weight of components A to D is 100% by weight.

Preferably, the amount of component A is from 20 to 95% by weight, more preferably 30 to 95% by weight.

The amount of component B is preferably 5 to 70% by weight, more preferably 5 to 50% by weight.

The amount of component C is preferably 0 to 50% by weight, more preferably 0 to 30% by weight. If component C is employed, the amount is 1 to 60% by weight, preferably 3 to 50% by weight, more preferably 5 to 30% by weight, in particular 5 to 20% by weight. The maximum amount of component A is in this case reduced by the minimum amount of component C.

The amount of component D is preferably from 0 to 40% by weight, more preferably 0 to 30% by weight. If component D is employed, the amount is 0.5 to 50% by weight, preferably 1 to 40% by weight, more preferably 2 to 30% by weight. If component D is employed, the maximum amount of component A is reduced by the minimum amount of component D.

Component A is at least one thermoplastic polymer. Preferably, the thermoplastic polymer is polyamide, polyester, polycarbonate, styrene polymer, polyurethane, polyolefin, polyketone, pol- ylactide, polyphenylene sulfide, polyimide, epoxy resin, silicone resin. Suitable thermoplastic polymers are for example described in EP 2935464 B1 in paragraphs [0010] and [0011]

Preferably, the thermoplastic polymer is polyamide, polyester, polycarbonate, styrene polymer, polyurethane, polyolefin, polyketone or a mixture thereof. More preferably, the thermoplastic polymer is polyamide, polyalkylene terephthalate or polyurethane.

The polyamides of the molding compositions of the invention generally have an viscosity num ber (VN) (or reduced viscosity) of from 90 to 350 ml/g, preferably from 90 to 240 ml/g, more preferably from 110 to 240 ml/g, determined in a 0.5% strength by weight solution in 96% strength by weight sulfuric acid at 25°C to ISO 307.

Preference is given to semicrystalline or amorphous resins with a molecular weight (weight av erage) of at least 5000, described by way of example in the following US patents: 2 071 250,

2 071 251 , 2 130523, 2 130948, 2241 322, 2312966, 2 512606, and 3393210. Examples of these are polyamides that derive from lactams having from 7 to 13 ring members, e.g. polycaprolactam, polycaprylolactam, and polylaurolactam, and also polyamides obtained via reaction of dicarboxylic acids with diamines.

Dicarboxylic acids which may be used are alkanedicarboxylic acids having from 4 to 40, prefer ably from 6 to 12, in particular from 6 to 10, carbon atoms, and aromatic dicarboxylic acids. Merely as examples, those that may be mentioned here are adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and terephthalic and/or isophthalic acid.

Particularly suitable diamines are alkanediamines having from 4 to 12, in particular from 6 to 8, carbon atoms, and also m-xylylenediamine (e.g. Ultramid^® X17 from BASF SE, where the molar ratio of MXDA to adipic acid is 1 :1), di(4-aminophenyl)methane, di(4-aminocyclohexyl)methane, 2,2-di(4-aminophenyl)propane, 2,2-di(4-aminocyclohexyl)propane, and 1 ,5-diamino-2-methyl- pentane.

Preferred polyamides are polyhexamethyleneadipamide, polyhexamethylenesebacamide, and polycaprolactam, and also nylon-6/6,6 copolyamides, in particular having a proportion of from 5 to 95% by weight of caprolactam units (e.g. Ultramid^® C31 from BASF SE).

Other suitable polyamides are obtainable from w-aminoalkylnitriles, e.g. aminocapronitrile (PA 6) and adipodinitrile with hexamethylenediamine (PA 66) via what is known as direct polymerization in the presence of water, for example as described in DE-A 10313681 , EP-A 1198491 and EP 922065.

Mention may also be made of polyamides obtainable, by way of example, via condensation of 1 ,4-diaminobutane with adipic acid at an elevated temperature (nylon-4,6). Preparation pro cesses for polyamides of this structure are described by way of example in EP-A 38 094, EP-A 38 582, and EP-A 39 524.

Other suitable examples are polyamides obtainable via copolymerization of two or more of the abovementioned monomers, and mixtures of two or more polyamides in any desired mixing ra tio. Particular preference is given to mixtures of nylon-6,6 with other polyamides, in particular nylon-6/6,6 copolyamides.

Other copolyamides which have proven particularly advantageous are semiaromatic copolyami des, such as PA 6T/6 and PA 6T/66, where the triamine content of these is less than 0.5% by weight, preferably less than 0.3% by weight (see EP-A 299444). Other polyamides resistant to high temperatures are known from EP-A 19 94 075 (PA 6T/6I/MXD6).

The following list, which is not comprehensive, comprises the polyamides A) mentioned and other polyamides A) for the purposes of the invention, and the monomers comprised: AB polymers:

PA 4 Pyrrolidone PA 6 e-Caprolactam PA 7 Ethanolactam PA 8 Caprylolactam PA 9 9-Aminopelargonic acid PA 11 11-Aminoundecanoic acid PA 12 Laurolactam

AA/BB polymers: PA 46 Tetramethylenediamine, adipic acid PA 56 Pentamethylenediamine, adipic acid PA 510 Pentamethylenediamine, sebacic acid PA 512 Pentamethylenediamine, decanedicarboxylic acid PA 66 Hexamethylenediamine, adipic acid PA 69 Hexamethylenediamine, azelaic acid PA 610 Hexamethylenediamine, sebacic acid PA 612 Hexamethylenediamine, decanedicarboxylic acid PA 613 Hexamethylenediamine, undecanedicarboxylic acid PA 1212 1.12-Dodecanediamine, decanedicarboxylic acid PA 1313 1.13-Diaminotridecane, undecanedicarboxylic acid PA 6T Hexamethylenediamine, terephthalic acid PA MXD6 m-Xylylenediamine, adipic acid PA 9T Nonamethylenediamine, terephthalic acid

AA/BB polymers:

Hexamethylenediamine, isophthalic acid Trimethylhexamethylenediamine, terephthalic acid (see PA 6 and PA 6T)

(see PA 6 and PA 66)

(see PA 6 and PA 12)

(see PA 66, PA 6 and PA 610)

(see PA 6I and PA 6T)

Diaminodicyclohexylmethane, laurolactam as PA 6I/6T + diaminodicyclohexylmethane Caprolactam/hexamethylenediamine, C36-dicarboxylic acid (see PA 6T and PA 66)

Laurolactam, dimethyldiaminodicyclohexylmethane, isophthalic acid Laurolactam, dimethyldiaminodicyclohexylmethane, terephthalic acid

Phenylenediamine, terephthalic acid

Most preferred are PA 6, PA 66, PA 6/66, PA 66/6, PA 6/6.36, PA 6I/6T, PA 6T/6I, PA 9T and PA 6T/66. Polyalkylene terephthalates are preferably poly C2-6-alkyl terephthalates, more preferably poly ethylene terephthalate, polybutylene terephthalate or mixtures thereof. They have preferably a viscosity number in the range of from 50 to 220, preferably from 70 to 160 (measured in 0.5% by weight solution in a phenol-o-dichlorobenzene mixture (ratio by weight 1 :1 at 25°C) in ac cordance with ISO 1628.

For injection molding, viscosity numbers in the range of from 70 to 130 cm³/g, more preferably in the range of from 75 to 115 cm³/g are preferred.

For a further disclosure of suitable polyalkylene terephthalates, reference can be made to WO 2019/068597 and the literature cited therein.

Suitable thermoplastic polyurethanes are for example described in WO 2014/147194 and WO 2013/182555. Polyurethanes are furthermore disclosed in WO 2018/177941,

WO 2018/189088.

Also precursors of organic polymers can contain the aluminium particles. An example is a polyol composition for producing polyurethanes.

The invention also relates to a polyol composition for producing polyurethanes, comprising a’) from 5 to 99% by weight of at least one polyol, as component A’, b’) from 1 to 90% by weight of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thickness of 1 to 200 nm, as component B’, c’) from 0 to 30% by weight of further additives, as component C’, where the total of the percentages by weight of components A’ to C’ is 100% by weight.

The polyol can be as described in WO 2018/189088 or WO 2019/234065. These documents also disclose possible chain extenders, cross linkers, catalysts, and if desired, blowing agents and surface-active substances as well as nucleating agents.

As compounds A’ which are reactive towards isocyanates, it is possible to use generally known polyhydroxyl compounds, preferably ones having a functionality towards isocyanate groups of from 2 to 3 and preferably a molecular weight of from 60 to 6000, particularly preferably from 500 to 6000, in particular from 800 to 3500. Preference is given to using generally known poly ether polyols, polyester polyols, polyether ester polyols and/or hydroxyl-comprising polycar bonates as (b). Particular preference is given to using polyester polyols, polytetrahydrofuran (PTHF) and polypropylene glycol (PPG), which typically contain the magnetizable particles.

Suitable polyester polyols can, for example, be prepared from dicarboxylic acids having from 2 to 12 carbon atoms and dihydric alcohols. Examples of possible dicarboxylic acids are: adipic acid, phthalic acid, maleic acid. Examples of dihydric alcohols are glycols having from 2 to 16 carbon atoms, preferably from 2 to 6 carbon atoms, e.g. ethylene glycol, diethylene glycol, 1 ,4- butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,10-decanediol, 1 ,3-propanediol and dipropylene glycol. Depending on the desired properties, the dihydric alcohols can be used either alone or, if appropriate, in mixtures with one another. As polyester polyols, preference is given to using ethanediol polyadipates, 1 ,4-butanediol polyadipates, ethanediol-butanediol polyadipates, 1 ,6- hexanediol-neopentyl glycol polyadipates, 1 ,6-hexanediol-1 ,4-butanediol polyadipates and/or polycaprolactones.

Suitable polyoxyalkylene glycols, essentially polyoxytetramethylene glycols, comprising ester groups are polycondensates of organic, preferably aliphatic dicarboxylic acids, in particular adipic acid, with polyoxymethylene glycols having a number average molecular weight of from 162 to 600 and, if appropriate, aliphatic diols, in particular 1 ,4-butanediol. Further suitable poly oxytetramethylene glycols comprising ester groups are polycondensates derived from polycon densation with e-caprolactone. Suitable polyoxyalkylene glycols, essentially polyoxytetrameth ylene glycols, comprising carbonate groups are polycondensates of these with alkyl or aryl car bonates or phosgene.

Information on the component A’ is provided by way of example in DE-A 195 48 771 , page 6, lines 26 to 59.

When fillers are mixed with polyols, they typically separate after a short time, and stable disper sions cannot be obtained. In order to obtain stable dispersions, a stabilizer is normally neces sary.

A polyester polyol which can react with the aluminium particles inherently stabilizes the particles in the polyester polyol dispersion. Only part of the polyester polyol is reacted with the particles, thus forming the continuous dispersing medium as well as being part of the dispersed particles. The polyester polyol reacted with the particles can be regarded as a stabilizer which stabilizes the dispersions of particles in polyols, specifically polyester polyols, so that a stable dispersion is achieved and precipitation of the particles is prevented. Thus, by the process of the present invention, a stable dispersion is obtained. Besides the polyester polyol as dispersing medium, additional polyols may be present in the dispersion or added to the dispersion after the mechan ical mixing with the particles. Suitable polyols can be further polyester polyols or polyether poly ols. Preferably, no additional polyester polyols or polyether polyols are employed, but the part of the polyester polyol not reacted with the particles forms the continuous dispersing medium.

The stable dispersion of the aluminium particles can be preferably obtained, when a polyester polyol is employed having an acid number in the range of 0.05 to 1.5, preferably from 0.01 to 1 .0, more preferably from 0.3 to 0.9.

The acid number is determined by DIN EN 12634 (DIN standard of the Deutsches Institut fur Normung e.V.) from 1999 and refers to mg_KOH/g _oiymer. The unit is included in the meaning of the above numbers. The acid number relates to the total of the polyester polyol. Thus, the polyester polyol can be one single-type of carboxyl group containing polyol. It can, however, also be a combination of a polyol having higher amounts of carboxyl groups in admixture with polyols having lesser amounts carboxyl groups or no carboxyl groups at all.

The lower the acid number, the better the polyurethane (PU) preparation becomes, since basic PU catalysts may be neutralized by the acid and accordingly higher amounts are required.

By employing polyols that have acidic (carboxylic acid) groups, the S1O2 coated aluminium parti cles can bind to these sites and therefore, the polyester polyol can act as a stabilizer for the dis persion of the inorganic oxide particles.

Preferably, the polyester polyol employed according to the present invention has a hydroxyl number in the range of from 10 to 150, more preferably 30 to 100, most preferably 40 to 90. The hydroxyl number is determined in accordance with DIN 53240 from 2012. It is determined in

This unit is included in the meaning of the above numbers.

The hydroxyl number equally relates to the total of the polyol, confirming the above statement.

Suitable molecular weight ranges for the polyester polyols employed for the purposes of the present invention are known per se to a person skilled in the art. Preferably, the polyester polyol has a molecular weight (M_n) of from 500 to 30000 g/mol, more preferably 500 to 4000 g/mol, most preferably 800 to 3000 g/mol and specifically in the range of from 1000 to 2500 g/mol. As an alternative, a preferred polyester polyol can have a molecular weight (M_n) of from 10000 to 25000 g/mol. For instance, the molecular weight (M_n) can be determined by gel permeation chromatography using polystyrene as standard and tetrahydrofuran (THF) as eluent solvent.

In the present invention, the polyester polyol is based on a polyhydric alcohol. Suitable polyhy- dric alcohols include, for example, polyhydric aliphatic alcohols, for example aliphatic alcohols having 2, 3, 4 or more OFI groups, for example 2 or 3 OFI groups. Suitable aliphatic alcohols for the purposes of the present invention include, for example, C2 to C12 alcohols, preferably C2 to Cs alcohols and most preferably C2 to C_& alcohols. It is preferable for the purposes of the pre sent invention for the polyhydric alcohol to be a diol, and suitable diols are known per se to a person skilled in the art.

Suitable aliphatic C2 to C_& diols include, for example, ethylene glycol, diethylene glycol, 3- oxapentane-1 ,5-diol, 1,3-propanediol, 1,2-propanediol, dipropylene glycol, 1,4-butanediol, 1,5- pentanediol, 1,6-hexanediol, 2-methyl-1 ,3-propanediol and 3-methyl-1,5-pentanediol. It is fur ther preferable for the polyhydric alcohol to be selected from the group consisting of 1 ,3-pro- panediol and 1,4-butanediol. In one further embodiment, the at least one polyhydric alcohol is selected from the group con sisting of aliphatic C2 to C₆ diols.

In one further embodiment, the at least one polyhydric alcohol is selected from the group con sisting of 1,3-propanediol and 1,4-butanediol.

It is also possible for the purposes of the present invention to employ a polyhydric alcohol at least partly obtained from renewable raw materials. The polyhydric alcohol in question may be partly or wholly obtained from renewable raw materials. It is also possible to employ a mixture of two or more polyhydric alcohols in the present invention. Where a mixture of two or more poly hydric alcohols is employed, one or more of the polyhydric alcohols employed may be at least partly obtained from renewable raw materials.

1 ,3-Propanediol may accordingly comprise synthetically produced 1,3-propanediol, but in partic ular 1 ,3-propanediol from renewable raw materials (“biobased 1 ,3-propanediol”). Biobased 1 ,3- propanediol is obtainable from maize (corn) and/or sugar for example. A further possibility is the conversion of waste glycerol from biodiesel production. In one further preferred embodiment of the invention, the polyhydric alcohol is a 1 ,3-propanediol at least partly obtained from renewable raw materials.

In one further embodiment, the at least one polyhydric alcohol is a 1 ,3-propanediol at least partly obtained from renewable raw materials.

Alcohols having three or more OH groups can also be used to enhance the functionality of the polyester polyols. Examples of alcohols having three or more OH groups are glycerol, trime- thylolpropane and pentaerythritol. It is also possible to use oligomeric or polymeric products having two or more hydroxyl groups. Examples thereof are polytetrahydrofuran, polylactones, polyglycerol, polyetherols, polyesterol or a,w-dihydroxypolybutadiene.

Possible preferred starter molecules are 2- to 8-functional alcohols, such as ethylene glycol,

1 ,2- and 1 ,3-propane diol, diethylene glycol, dipropylene glycol, 1 ,4-butane diol, glycerol or di- methylol propane, sugars, sorbitol or pentaerythritol.

Suitable polyester polyols can, for example, be prepared from dicarboxylic acids having from 2 to 12 carbon atoms and dihydric alcohols. Examples of possible dicarboxylic acids are: adipic acid, phthalic acid, maleic acid. Examples of dihydric alcohols are glycols having from 2 to 16 carbon atoms, preferably from 2 to 6 carbon atoms, e.g. ethylene glycol, diethylene glycol, 1,4- butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 ,10-decanediol, 1,3-propanediol and dipropylene glycol. Depending on the desired properties, the dihydric alcohols can be used either alone or, if appropriate, in mixtures with one another. As polyester polyols, preference is given to using ethanediol polyadipates, 1 ,4-butanediol polyadipates, ethanediol-butanediol polyadipates, 1 ,6- hexanediol-neopentyl glycol polyadipates, 1 ,6-hexanediol-1 ,4-butanediol polyadipates and/or polycaprolactones. Suitable polyoxyalkylene glycols, essentially polyoxytetramethylene glycols, comprising ester groups are polycondensates of organic, preferably aliphatic dicarboxylic acids, in particular adipic acid, with polyoxymethylene glycols having a number average molecular weight of from 162 to 600 and, if appropriate, aliphatic diols, in particular 1 ,4-butanediol. Further suitable poly oxytetramethylene glycols comprising ester groups are polycondensates derived from polycon densation with e-caprolactone. Suitable polyoxyalkylene glycols, essentially polyoxytetramethy lene glycols, comprising carbonate groups are polycondensates of these with alkyl or aryl car bonates or phosgene.

In a polyurethane reactive system, the polyol component A’ is combined with isocyanates.

As isocyanates, it is possible to use generally known (cyclo)aliphatic and/or aromatic polyisocy anates. Particularly suitable polyisocyanates for producing the composite elements according to the invention are aromatic diisocyanates, preferably diphenylmethane 2,2'-, 2,4'- and/or 4,4'- diisocyanate (MDI), naphthylene 1 ,5-diisocyanate (NDI), toluoylene 2,4- and/or 2,6-diisocyanate (TDI), 3,3'-dimethylbiphenyl diisocyanate (tolidine diisocyanate (TODI)), 1 ,2-diphenylethane diisocyanate, p-phenylene diisocyanate and/or (cyclo)aliphatic isocyanates such as hexameth- ylene 1 ,6-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane and/or pol yisocyanates such as polyphenylpolymethylene polyisocyanates. The isocyanates can be used in the form of the pure compound, in mixtures and/or in modified form, for example in the form of uret diones, isocyanurates, allophanates or biuretes, preferably in the form of reaction prod ucts comprising urethane and isocyanate groups, known as isocyanate prepolymers. Prefer ence is given to using optionally modified diphenylmethane 2,2'-, 2,4'- and/or 4,4'-diisocyanate (MDI), naphthylene 1 ,5-diisocyanate (NDI), toluoylene 2,4- and/or 2,6-diisocyanate (TDI), toli dine diisocyanate (TODI), and/or mixtures of these isocyanates.

Further additives of component C’ can be the below additives mentioned as component D. Component B are the above-mentioned aluminium particles.

As component C, at least one fibrous or particulate filler which is different from component B can be employed.

Fibrous or particulate fillers that may be mentioned are glass fibers, glass beads, amorphous silica, calcium silicate, calcium metasilicate, magnesium carbonate, magnesium oxide, kaolin, chalk, powdered quartz, mica, barium sulfate, and feldspar. Spherical magnesium oxide parti cles are preferred.

Preferably, component C comprises 1 to 25% by weight, more preferably 2 to 15% by weight, most preferably 3 to 10% by weight, based on the total of percentages by weight of components A to D which is 100% by weight, of a particulate ceramic filler, preferably spherical MgO. Preferred fibrous fillers that may be mentioned are aramid fibers, and potassium titanate fibers, particular preference being given to glass fibers in the form of E glass. These can be used as rovings or in the commercially available forms of chopped glass.

The fibrous fillers may have been surface-pretreated with a silane compound to improve com patibility with the thermoplastic.

Suitable silane compounds have the general formula:

(X-(CH₂)n)k-Si-(0-C_mH₂m_+l)4-k where the definitions of the substituents are as follows:

n is a whole number from 2 to 10, preferably 3 to 4, m is a whole number from 1 to 5, preferably 1 to 2, and k is a whole number from 1 to 3, preferably 1.

Preferred silane compounds are aminopropyltrimethoxysilane, aminobutyltrimethoxysilane, ami- nopropyltriethoxysilane and aminobutyltriethoxysilane, and also the corresponding silanes which comprise a glycidyl group as substituent X.

The amounts of the silane compounds generally used for surface-coating are from 0.01 to 2% by weight, preferably from 0.025 to 1.0% by weight and in particular from 0.05 to 0.5% by weight (based on the glass fibers)).

Acicular mineral fillers are also suitable.

For the purposes of the invention, acicular mineral fillers are mineral fillers with strongly devel oped acicular character. An example is acicular wollastonite. The mineral preferably has an L/D (length to diameter) ratio of from 8:1 to 35:1, preferably from 8:1 to 11:1. The mineral filler may optionally have been pretreated with the abovementioned silane compounds, but the pretreat ment is not essential.

Other fillers which may be mentioned are kaolin, calcined kaolin, wollastonite, talc and chalk, and also lamellar or acicular nanofillers, the amounts of these preferably being from 0.1 to 10%. Materials preferred for this purpose are boehmite, bentonite, montmorillonite, vermiculite, hec- torite, and laponite. The lamellar nanofillers are organically modified by prior-art methods, to give them good compatibility with the organic binder. Addition of the lamellar or acicular nano fillers to the inventive nanocomposites gives a further increase in mechanical strength. As component D, the thermoplastic molding compositions can comprise further additives.

The thermoplastic molding compositions of the invention can comprise, as component D, con ventional processing aids, such as stabilizers, oxidation retarders, agents to counteract decom position by heat and decomposition by ultraviolet light, lubricants and mold-release agents, col orants, such as dyes and pigments, nucleating agents, plasticizers, etc.

The molding compositions of the invention can comprise, as component D, from 0.05 to 3% by weight, preferably from 0.1 to 1.5% by weight, and in particular from 0.1 to 1 % by weight, of a lubricant.

Preference is given to the salts of Al, of alkali metals, or of alkaline earth metals, or esters or amides of fatty acids having from 10 to 44 carbon atoms, preferably having from 12 to 44 car bon atoms.

The metal ions are preferably alkaline earth metal and Al, particular preference being given to Ca or Mg.

Preferred metal salts are Ca stearate and Ca montanate, and also Al stearate.

It is also possible to use a mixture of various salts, in any desired mixing ratio.

The carboxylic acids can be monobasic or dibasic. Examples which may be mentioned are pel- argonic acid, palmitic acid, lauric acid, margaric acid, dodecanedioic acid, behenic acid, and particularly preferably stearic acid, capric acid, and also montanic acid (a mixture of fatty acids having from 30 to 40 carbon atoms).

The aliphatic alcohols can be monohydric to tetrahydric. Examples of alcohols are n-butanol, n- octanol, stearyl alcohol, ethylene glycol, propylene glycol, neopentyl glycol, pentaerythritol, pref erence being given to glycerol and pentaerythritol.

The aliphatic amines can be mono- to tribasic. Examples of these are stearylamine, ethylenedi- amine, propylenediamine, hexamethylenediamine, di(6-aminohexyl)amine, particular preference being given to ethylenediamine and hexamethylenediamine. Preferred esters or amides are cor respondingly glycerol distearate, glycerol tristearate, ethylenediamine distearate, glycerol mono- palmitate, glycerol trilaurate, glycerol monobehenate, and pentaerythritol tetrastearate.

It is also possible to use a mixture of various esters or amides, or of esters with amides in com bination, in any desired mixing ratio.

The molding compositions of the invention can comprise, as component D, from 0.05 to 3% by weight, preferably from 0.1 to 1.5% by weight, and in particular from 0.1 to 1 % by weight, of a copper stabilizer, preferably of a Cu(l) halide, in particular in a mixture with an alkali metal hal ide, preferably Kl, in particular in the ratio 1 :4, or of a sterically hindered phenol, or a mixture of these.

Preferred salts of monovalent copper used are cuprous acetate, cuprous chloride, cuprous bro mide, and cuprous iodide. The materials comprise these in amounts of from 5 to 500 ppm of copper, preferably from 10 to 250 ppm, based on polyamide.

The advantageous properties are in particular obtained if the copper is present with molecular distribution in the polymer, e.g. polyamide. This is achieved if a concentrate comprising the pol yamide, and comprising a salt of monovalent copper, and comprising an alkali metal halide in the form of a solid, homogeneous solution is added to the molding composition. By way of ex ample, a typical concentrate is composed of from 79 to 95% by weight of polyamide and from 21 to 5% by weight of a mixture composed of copper iodide or copper bromide and potassium iodide. The copper concentration in the solid homogeneous solution is preferably from 0.3 to 3% by weight, in particular from 0.5 to 2% by weight, based on the total weight of the solution, and the molar ratio of cuprous iodide to potassium iodide is from 1 to 11 .5, preferably from 1 to 5.

Suitable polyamides for the concentrate are homopolyamides and copolyamides, in particular nylon-6 and nylon-6,6.

Examples of oxidation retarders and heat stabilizers are sterically hindered phenols and/or phosphites and amines (e.g. TAD), hydroquinones, aromatic secondary amines, such as diphe- nylamines, various substituted members of these groups, and mixtures of these, in concentra tions of up to 1 % by weight, based on the weight of the thermoplastic molding compositions.

Suitable sterically hindered phenols are in principle all of the compounds which have a phenolic structure and which have at least one bulky group on the phenolic ring.

It is preferable to use, for example, compounds of the formula

where:

R¹ and R² are an alkyl group, a substituted alkyl group, or a substituted triazole group, and where the radicals R¹ and R² may be identical or different, and R³ is an alkyl group, a substi tuted alkyl group, an alkoxy group, or a substituted amino group.

Antioxidants of the abovementioned type are described by way of example in DE-A 27 02 661 (US-A 4 360 617). Another group of preferred sterically hindered phenols is provided by those derived from substi tuted benzenecarboxylic acids, in particular from substituted benzenepropionic acids. Particularly preferred compounds from this class are compounds of the formula

where R⁴, R⁵, R⁷, and R⁸, independently of one another, are Ci-Cs-alkyl groups which them- selves may have substitution (at least one of these being a bulky group), and R⁶ is a divalent aliphatic radical which has from 1 to 10 carbon atoms and whose main chain may also have C- O bonds.

Preferred compounds corresponding to these formulae are

(Irganox^® 259 from BASF SE)

All of the following should be mentioned as examples of sterically hindered phenols: 2,2’-methylenebis(4-methyl-6-tert-butylphenol), 1 ,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxy- phenyl)propionate], pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dis- tearyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 2,6,7-trioxa-1 -phosphabicyclo[2.2.2]oct-4- ylmethyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, 3,5-di-tert-butyl-4-hydroxyphenyl-3,5-distea- rylthiotriazylamine, 2-(2’-hydroxy-3’-hydroxy-3’,5’-di-tert-butylphenyl)-5-chlorobenzotriazole, 2,6- di-tert-butyl-4-hydroxymethylphenol, 1 ,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)- benzene, 4,4’-methylenebis(2,6-di-tert-butylphenol), 3,5-di-tert-butyl-4-hydroxybenzyldimethyla- mine.

Compounds which have proven particularly effective and which are therefore used with prefer ence are 2,2’-methylenebis(4-methyl-6-tert-butylphenol), 1 ,6-hexanediol bis(3,5-di-tert-butyl-4- hydroxyphenyl)propionate (Irganox^® 259), pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxy- phenyl)propionate], and also N,N’-hexamethylenebis-3,5-di-tert-butyl-4-hydroxyhydrocinnamide (Irganox^® 1098), and the product Irganox^® 245 described above from BASF SE, which has par ticularly good suitability.

The amount comprised of the antioxidants D, which can be used individually or as a mixture, is from 0.05 up to 3% by weight, preferably from 0.1 to 1.5% by weight, in particular from 0.1 to 1 % by weight, based on the total weight of the molding compositions A to D.

In some instances, sterically hindered phenols having not more than one sterically hindered group in ortho-position with respect to the phenolic hydroxy group have proven particularly ad vantageous; in particular when assessing colorfastness on storage in diffuse light over pro longed periods.

Examples of other conventional additives D are amounts of up to 25% by weight, preferably up to 20% by weight, of elastomeric polymers (also often termed impact modifiers, elastomers, or rubbers).

These are very generally copolymers preferably composed of at least two of the following mon omers: ethylene, propylene, butadiene, isobutene, isoprene, chloroprene, vinyl acetate, styrene, acrylonitrile and acrylates and/or methacrylates having from 1 to 18 carbon atoms in the alcohol component.

Polymers of this type are described, for example, in Houben-Weyl, Methoden der organischen Chemie, vol. 14/1 (Georg-Thieme-Verlag, Stuttgart, Germany, 1961), pages 392 to 406, and in the monograph by C. B. Bucknall, "Toughened Plastics" (Applied Science Publishers, London, UK, 1977).

Some preferred types of such elastomers are described below.

Preferred types of such elastomers are those known as ethylene-propylene (EPM) and ethyle- ne-propylene-diene (EPDM) rubbers.

EPM rubbers generally have practically no residual double bonds, whereas EPDM rubbers may have from 1 to 20 double bonds per 100 carbon atoms. EPM rubbers and EPDM rubbers may preferably also have been grafted with reactive carbox ylic acids or with derivatives of these. Examples of these are acrylic acid, methacrylic acid and derivatives thereof, e.g. glycidyl (meth)acrylate, and also maleic anhydride.

Copolymers of ethylene with acrylic acid and/or methacrylic acid and/or with the esters of these acids are another group of preferred rubbers.

Other preferred elastomers are emulsion polymers whose preparation is described, for exam ple, by Blackley in the monograph "Emulsion Polymerization". The emulsifiers and catalysts which can be used are known per se.

In principle it is possible to use homogeneously structured elastomers or else those with a shell structure. The shell-type structure is determined by the sequence of addition of the individual monomers. The morphology of the polymers is also affected by this sequence of addition.

Preference is also given to silicone rubbers, as described in DE-A 3725576, EP-A 235690, DE-A 3800603 and EP-A 319290.

It is, of course, also possible to use mixtures of the types of rubber listed above.

UV stabilizers that may be mentioned, the amounts of which used are generally up to 2% by weight, based on the molding composition, are various substituted resorcinols, salicylates, ben- zotriazoles, and benzophenones.

Materials that can be added as colorants are inorganic pigments, such as titanium dioxide, ultra- marine blue, iron oxide, and carbon black, and also organic pigments, such as phthalocyanines, quinacridones, perylenes, and also dyes, such as anthraquinones.

Materials that can be used as nucleating agents are sodium phenylphosphinate, aluminum ox ide, silicon dioxide, and also preferably talc.

It is possible to use any suitable flame retardants as component D.

Red phosphorus as example of a preferred flame retardant

Red phosphorus is such a preferred flame retardant. It can be used in untreated form, in partic ular in conjunction with fiber-reinforced molding compositions.

The red phosphorus can also be coated with low molecular weight liquid substances such as silicone oil, paraffin oil or esters of phthalic acid or adipic acid or with polymeric or oligomeric compounds such as phenolic resins or amino plastics or else with polyurethanes. The propor tion of these agents is generally from 0.05 to 5% by weight, based on the red phosphorus. Red phosphorus can also be used in the form of concentrates. Such concentrates can comprise from 30 to 90% by weight, preferably from 45 to 70% by weight, of a polyamide or elastomer and from 10 to 70% by weight, preferably from 30 to 55% by weight, of red phosphorus. Red phosphorus can also be present in aqueous solution or suspension of the respective addi tive, in which case it is filtered off, washed with water and dried before use. The average particle size (D50) of phosphorus particles dispersed in molding compositions is preferably in the range from 0.0001 to 0.5 mm, preferably from 0.001 to 0.2 mm. Examples of preferred flame retardants of the component D are metal phosphinates which are derived from hypophosphorous acid. For example, it is possible to use a metal salt of hypophos- phorous acid with Mg, Ca, Al or Zn as metal. Particular preference is given here to aluminum hypophosphite. Phosphinic acid salts of the formula (I) or/and diphosphinic acid salts of the formula (II) or poly mers thereof

where

R¹, R² are identical or different and are each hydrogen, Ci-C₆-alkyl, linear or branched, or aryl;

R³ is Ci-Cio-alkylene, linear or branched, C₆-Cio-arylene, -alkylarylene or -arylalkylene;

M is Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Sr, Mn, Li, Na, K and/or a protonated nitrogen base; m is from 1 to 4; n is from 1 to 4; x is from 1 to 4, preferably m = 3, x = 3, are also suitable. Preference is given to R¹, R² of the component B being identical or different and each being hy drogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl or phenyl.

R³ of the component B is preferably methylene, ethylene, n-propylene, isopropylene, n-butyl- ene, tert-butylene, n-pentylene, n-octylene or n-dodecylene, phenylene or naphthylene; methylphenylene, ethylphenylene, tert-butylphenylene, methylnaphthylene, ethylnaphthylene or tert-butylnaphthylene; phenylmethylene, phenylethylene, phenylpropylene or phenylbutylene.

Particular preference is given to R¹, R² being hydrogen, methyl, ethyl and M being Al, with Al hy- pophosphite being particularly preferred.

The phosphinates are preferably prepared by precipitation of the appropriate metal salts from aqueous solutions. However, the phosphinates can also be precipitated in the presence of a suitable inorganic metal oxide or sulfide as support material (white pigments such as TiC>2,

SnC>2, ZnO, ZnS, S1O2). This gives surface-modified pigments which can be used as laser-mark- able flame retardants for thermoplastic polyesters.

Preference is given to using metal salts of substituted phosphinic acids in which, compared to hypophosphorous acid, one or two hydrogen atoms have been replaced by phenyl, methyl, ethyl, propyl, isobutyl, isooctyl or R’-CH-OH radicals where R‘ is hydrogen, phenyl, tolyl. The metal is preferably Mg, Ca, Al, Zn, Ti, Fe. Particular preference is given to aluminum dieth- ylphosphinate (DEPAL).

For a description of phosphinic acid salts or diphosphinic acid salts, reference may be made to DE-A-199 60 671 and also DE-A-44 30 932 and DE-A-199 33 901.

Suitable halogen-comprising flame retardants are preferably brominated compounds such as brominated diphenyl ether, brominated trimethylphenylindanes (FR 1808 from DSB), tetrabro- mobisphenol A and hexabromocyclododecane.

Suitable flame retardants are preferably brominated compounds such as brominated oligocar- bonates (BC 52 or BC 58 from Great Lakes) of the structural formula:

Polypentabromobenzyl acrylates having n > 4 (e.g. FR 1025 from ICL-IP) of the formula: are particularly suitable.

Preferred brominated compounds also include oligomeric reaction products (n > 3) of tetrabro- mobisphenol A with epoxides (e.g. FR 2300 and 2400 from DSB) of the formula:

The brominated oligostyrenes which are preferably used as flame retardants have an average degree of polymerization (number average) in the range from 3 to 90, preferably from 5 to 60, measured by vapor pressure osmometry in toluene. Cyclic oligomers are likewise suitable. In a preferred embodiment of the invention, the brominated oligomeric styrenes to be used have the formula I below, where R is hydrogen or an aliphatic radical, in particular an alkyl radical such as Chh or C₂H₅, and n is the number of repeating building blocks in the chain. R¹ can be either H or bromine or else a fragment of a conventional free-radical former:

The value of n can be 1-88, preferably 3-58. The brominated oligostyrenes comprise from 40 to 80% by weight, preferably from 55 to 70% by weight, of bromine. Preference is given to a prod uct which consists predominantly of polydibromostyrene. The substances can be melted without decomposition and are soluble in, for example, tetrahydrofuran. They can be prepared either by ring bromination of optionally aliphatically hydrogenated styrene oligomers as are obtained, for example, by thermal polymerization of styrene (as per DT-A 25 37 385) or by free-radical oli gomerization of suitable brominated styrenes. The preparation of the flame retardant can also be carried out by ionic oligomerization of styrene and subsequent bromination. The amount of brominated oligostyrene necessary for making the polyamides flame resistant depends on the bromine content. The bromine content in the molding compositions of the invention is from 2 to 30% by weight, preferably from 5 to 12% by weight.

The brominated polystyrenes according to the invention are usually obtained by the process de scribed in EP-A 47 549:

The brominated polystyrenes which can be obtained by this process and commercially are pre dominantly ring-substituted tribrominated products n' (see III) generally has values of from 125 to 1500, corresponding to a molecular weight of from 42 500 to 235 000, preferably from 130 000 to 135 000.

The bromine content (based on the content of ring-substituted bromine) is generally at least 50% by weight, preferably at least 60% by weight and in particular 65% by weight.

The commercially available pulverulent products generally have a glass transition temperature of from 160 to 200°C and can be obtained, for example, under the names HP 7010 from Albe marle and Pyrocheck PB 68 from Ferro Corporation.

It is also possible to use mixtures of the brominated oligostyrenes with brominated polystyrenes in the molding compositions of the invention, with any mixing ratio being possible.

Further suitable flame retardants are chlorine-comprising flame retardants, with Declorane plus from Oxychem being preferred.

Suitable halogen-comprising flame retardants are preferably ring-brominated polystyrene, bro minated polybenzyl acrylates, brominated bisphenol A-epoxide oligomers or brominated bi- sphenol A polycarbonates.

Another possibility is a nitrogen compound, preferably a melamine compound, for example mel amine borate, melamine phosphate, melamine sulfate, melamine pyrophosphate, melamine pol yphosphate, melam, melem, melon or melamine cyanurate. The melamine cyanurate which is preferably suitable for the purposes of the invention is a reac tion product of preferably equimolar amounts of melamine (formula I) and cyanuric acid or iso- cyanuric acid (formulae la and lb)

(la) (lb)

Enol form Keto form

It is obtained, for example, by reaction of aqueous solutions of the starting compounds at from 90 to 100°C. The commercially available product is a white powder having an average particle size dso of 1 .5-7 pm and a dgg value of less than 50 pm.

Further suitable compounds (often also referred to as salts or adducts) are melamine sulfate, melamine, melamine borate, oxalate, phosphate prim., phosphate sec. and pyrophosphate sec., neopentyl glycol boric acid melamine and polymeric melamine phosphate (CAS No. 56386-64-2 or 218768-84-4).

Preference is given to melamine polyphosphate salts of a 1 ,3,5-triazine compound in which the number n of the average degree of condensation is in the range from 20 to 200 and the 1 ,3,5- triazine content is from 1 .1 to 2.0 mol of a 1 ,3,5-triazine compound selected from the group con sisting of melamine, melam, melem, melon, ammeline, ammelide, 2-ureidomelamine, acetoguanamine, benzoguanamine and diaminophenyltriazine, per mole of phosphorous atoms. The n value of such salts is generally in the range from 40 to 150 and the ratio of a 1 ,3,5-tria- zine compound per mole of phosphorous atoms is preferably in the range from 1.2 to 1 .8. Fur thermore, the pH of a 10% strength by weight aqueous slurry of salts prepared as described in EP-B1095030 will generally be more than 4.5 and preferably at least 5.0. The pH is usually de termined by 25 g of the salt and 225 g of clean water at 25°C being placed in a 300 ml beaker stirring the resulting aqueous slurry for 30 minutes and then measuring the pH. The abovemen- tioned n value, viz. the number average degree of condensation, can be determined by means of solid-state ³¹P-NMR. It is known from J. R. van Wazer, C. F. Callis, J. Shoolery and R. Jones, J. Am. Chem. Soc., 78, 5715, 1956, that the number of adjacent phosphate groups gives a unique, chemical shift which allows a clear distinction to be made between orthophosphates, pyrophosphates and polyphosphates. In addition, EP1095030B1 describes a process for pre paring the desired polyphosphate salt of a 1,3,5-triazine compound which has an n value of from 20 to 200 and a 1 ,3,5-triazine content of from 1.1 to 2.0 mol of a 1,3,5-triazine compound. This process comprises conversion of a 1,3,5-triazine compound by means of orthophosphoric acid into its orthophosphate salt, followed by dehydration and heat treatment in order to convert the orthophosphate salt into a polyphosphate of the 1,3,5-triazine compound. This heat treat ment is preferably carried out at a temperature of at least 300°C, preferably at least 310°C. In addition to orthophosphates of 1 ,3,5-triazine compounds, it is likewise possible to use other 1 ,3,5-triazine phosphates, including, for example, a mixture of orthophosphates and pyrophos phates.

Suitable guanidine salts are

CAS No.

G carbonate 593-85-1 G cyanurate prim. 70285-19-7

G phosphate prim. 5423-22-3

G phosphate sec. 5423-23-4

G sulfate prim. 646-34-4

G sulfate sec. 594-14-9

Pentaerythritol boric acid guanidine N.A.

Neopentyl glycol boric acid guanidine N.A. and also urea phosphate green 4861-19-2

Urea cyanurate 57517-11-0

Ammeline 645-92-1

Ammelide 645-93-2

Melem 1502-47-2

Melon 32518-77-7

For the purposes of the present invention, compounds include both, for example, benzoguana- mine itself and adducts or salts thereof and also the derivatives and adducts or salts thereof which are substituted on the nitrogen.

Further suitable compounds are ammonium polyphosphate (NFUPChj_n where n is from about 200 to 1000, preferably from 600 to 800, and tris(hydroxyethyl) isocyanurate (TFIEIC) of the for mula IV or the reaction products thereof with aromatic carboxylic acids Ar(COOH)_m, which can optionally be present in admixture with one another, where Ar is a monocyclic, bicyclic or tricyclic aromatic six-membered ring system and m is 2, 3 or 4.

Suitable carboxylic acids are, for example, phthalic acid, isophthalic acid, terephthalic acid,

1 ,3,5-benzenetricarboxylic acid, 1 ,2,4-benzenetricarboxylic acid, pyromellitic acid, mellophanic acid, prehnitic acid, 1 -naphthoic acid, 2-naphthoic acid, naphthalenedicarboxylic acids and an- thracenecarboxylic acids.

The preparation is carried out by reaction of tris(hydroxyethyl) isocyanurate with the acids, alkyl esters thereof or halides thereof as per the process of EP-A 584 567.

Such reaction products are mixtures of monomeric and oligomeric esters which may also be crosslinked. The degree of oligomerization is usually from 2 to about 100, preferably from 2 to 20. Preference is given to using mixtures of THEIC and/or reaction products thereof with phos phorus-comprising nitrogen compounds, in particular (NH4PC>3)n or melamine pyrophosphate or polymeric melamine phosphate. The mixing ratio of, for example, (NH4PC>3)n to THEIC is prefer ably from 90:50 to 10:50, in particular from 80:50 to 50:20 on a weight basis, based on the mix ture of components B1 ) of this type.

Further suitable compounds are benzoguanamine compounds of the formula V

(V),

where R,R' are linear or branched alkyl radicals having from 1 to 10 carbon atoms, preferably hydrogen, and in particular adducts thereof with phosphoric acid, boric acid and/or pyrophos- phoric acid.

Preference is also given to allantoin compounds of the formula VI where R,R' are as defined for formula V and also salts thereof with phosphoric acid, boric acid and/or pyrophosphoric acid, and also glycolurils of the formula VII or salts thereof with the abovementioned acids

where R is as defined for formula V. Suitable products are commercially available or can be obtained as described in DE-A 196 14 424.

The cyanoguanidine (formula VIII) which can be used according to the invention is obtained, for example, by reaction of calcium cyanamide with carbonic acid, with the cyanamide formed di- merizing to cyanoguanidine at pH 9-10.

CaNCN + H₂0 C0₂ H₂N-CN + CaC0₃

The commercially available product is a white powder having a melting point of from 209°C to 211 °C.

Particular preference is given to using melamine cyanurate (for example Melapur MC25 from BASF SE) or melamine polyphosphate (for example Melapur M200 from BASF SE). Furthermore, it is possible to use separate metal oxides such as antimony trioxide, antimony pentoxide, sodium antimonate and similar metal oxides. However, the use of such metal oxides is preferably dispensed with since they are already present in component B. For a description of pentabromobenzyl acrylate and antimony trioxide or antimony pentoxide, reference may be made to EP-A-0 624 626.

Furthermore, phosphorus, for example red phosphorus, can be used as component C. Flere, red phosphorus can be used, for example, in the form of a masterbatch.

Further possibilities are dicarboxylic acid salts of the formula

where

R¹ to R⁴ are each, independently of one another, halogen or hydrogen, with the proviso that at least one radical R¹ to R⁴ is halogen, x = 1 to 3, preferably 1 or 2, m = 1 to 9, preferably from 1 to 3, 6, 9, in particular from 1 to 3, n = 2 to 3,

M = alkaline earth metal, Ni, Ce, Fe, In, Ga, Al, Pb, Y, Zn, Hg.

Preferred dicarboxylic acid salts comprise, independently of one another, Cl or bromine or hy drogen as radicals R¹ to R⁴, with particular preference being given to all radicals R¹ to R⁴ being Cl or/and Br.

As metals M, preference is given to Be, Mg, Ca, Sr, Ba, Al, Zn, Fe.

Such dicarboxylic acid salts are commercially available or can be prepared by the process de scribed in US 3354 191.

Component D is preferably a phosphinic acid salt, a halogen-comprising flame retardant, phos phorus, a melamine compound or a mixture of two or more thereof. Component D can preferably be selected from among c1) aluminum diethylphosphinate and/or aluminum hypophosphite, c2) aluminum diethylphosphinate and/or aluminum phosphite in combination with at least one melamine compound, c3) red phosphorus, c4) polypentabromobenzyl acrylate.

As component D, it is possible to use flame retardant polymers. Such polymers are described, for example, in US 8,314,202 and have 1 ,2-bis[4-(2-hydroxyethoxy)phenyl]ethanone repeating units. A further suitable functional polymer for increasing the amount of carbon residue is poly(2,6-dimethyl-1 ,4-phenylene oxide) (PPPO).

The thermoplastic molding compositions of the invention can be produced by processes known per se, by mixing the starting components in conventional mixing apparatus, such as screw- based extruders, Brabender mixers, or Banbury mixers, and then extruding the same. After ex trusion, the extrudate can be cooled and pelletized. It is also possible to premix individual com ponents and then to add the remaining starting materials individually and/or likewise in the form of a mixture. The mixing temperatures are generally from 230 to 320Ό.

The thermoplastic molding compositions of the invention feature good processability together with good mechanical properties, and also markedly improved thermal conduction.

These materials are suitable for the production of moldings of any type. Some examples follow: cylinder head covers, motorcycle covers, intake manifolds, charge-air-cooler caps, plug con nectors, gearwheels, cooling-fan wheels, and cooling-water tanks.

In the electrical and electronic sector, polyamides can be used to produce plugs, plug parts, plug connectors, membrane switches, printed circuit board modules, microelectronic compo nents, coils, I/O plug connectors, plugs for printed circuit boards (PCBs), plugs for flexible printed circuits (FPCs), plugs for flexible integrated circuits (FFCs), high-speed plug connec tions, terminal strips, connector plugs, device connectors, cable-harness components, circuit mounts, circuit-mount components, three-dimensionally injection-molded circuit mounts, electri cal connection elements, and mechatronic components.

The invention is further illustrated by the following examples. Examples Example 1

Aluminium flakes having an average diameter of 20 to 30 pm and a thickness of approximately 200-500 nm were employed. The thickness of the S1O2 layer was 5-50 nm. The coated alumin ium particles were prepared as follows:

In contrast to non-coated aluminium powder, passivated aluminium powder having a S1O2 layer shows a homogeneous dispersion. The pure aluminium powder shows agglomerated struc tures.

The passivated aluminium powder has the following dimensions: D10 = 13.6 pm, D50 =

21.4 pm, D90 = 31.8 pm. In contrast, the agglomerated aluminium powder had values of D10 = 99.9 pm, D50 = 177.4 pm, D90 = 439.6 pm.

The mechanical properties of a polyamide-6 composite with 40 wt% aluminium powder are listed in the following Table 1.

Table 1. The mechanical properties of PA 6 composite with 40 wt% Al powder

Filler Tensile modulus Tensile strength Strain at break Charpy un-

(MPa) (MPa) (%) notched (kJ/m²)

Pure Al powder 5750 65.8 2.5 45.3

Passivated Al 8020 90.5 1.7 28.2

The employed polyamide-6 had a viscosity number VN of 142-158 ml/g, measured on a 0.5% strength by weight solution in 96% strength by weight of sulfuric acid at 25 °C to ISO307 (Ultra- mid B27 from BASF SE).

The SiC>2 passivation layer imparts a better dispersion to the aluminum powder, resulting in bet ter mechanical performance.

Example 2

Polyamide-6 (Ultramid^® B 27 of BASF SE) was mixed with hexa-boron nitride (h-BN) or the S1O2 passivated aluminium powder (Al) from Example 1. The flowability, mechanical and thermal properties are shown in the following Table 2. Table 2. Flowability, mechanical and thermal properties comparison Components 1 2 3 4 5 6 7

PA 6 100 80 60 40 80 60 56 h-BN 20 40 60

Al 20 40 44

Flowability & Mechanical & Thermal properties

Spiral flow 46 42 34 47 41 41 Density (g/cm³) 1.12 1.25 1.47 1.54 1.23 1.42 1.46 Tensile modulus 8400±

3220±6.8 5490±43 9650±34 13800±71 5590±49 8070±38 (MPa) 25.6

Tensile strength

84±0.49 59±0.36 58±0.26 51 ±0.69 92±0.24 93±0.75 91 ±1.15 (MPa)

Strain at break

13±0.07 4.7±0.03 1.8±0.04 0.5±0.02 4.9±0.03 1.9±0.06 1.7±0.06

(%)

Unnotched charpy unbreak 31 ±1.9 17±0.3 5.4±0.8 61 ±1.4 20±2.7 18±1.8 (kJ/m²)

TC in-plane

0.25 0.86 3.21 6.5 0.9 3.29 3.4 (W/mK)

TC through-plane

0.25 0.43 0.58 0.95 0.34 0.42 0.5 (W/mK)

Remarks: Testing samples are prepared from pellets produced on a ZSK18 extruder.

The tensile properties were determined in accordance with ISO 527 and Charpy impact strength with ISO 179 .

The in-plane thermal conductivity for the addition of h-BN and of Al are at the same level. The through-plane thermal conductivity for the Al flakes is lower since the filler is thinner than h-BN. Examples 3

Acid resistance

1 g of pure aluminium powder or S1O2 passivated aluminium powder of Example 1 was dis- persed in a round bottom flask containing 40 ml of 4 mol/l hydrochloric acid. Table 3 shows the comparison of the acid resistance performance. Table 3. The comparison of acid resistance performance between pure Al and passivated AL particles

Particle type Observation time Weight of water Generated hydrogen

(min) excluded (g) volume (ml)

Pure Al 17 180.38 180.38 Passivated Al 25 0 0

The non-passivated aluminum generated hydrogen due to the reaction with the acid. The pas sivated aluminium did not generate hydrogen. Thus, the passivation layer inhibits the corrosion in the presence of acid or water.

Example 4

Surface functionalization

With a silane coupling reaction, various functionalities including epoxy, maleic anhydride, amine can be applied to the S1O2 passivated aluminium particles of Example 1. A typical sizing proto col can be applied for the passivated aluminium, employing a silane coupling agent. Typically, trialkoxysilane is dissolved in water. If an epoxy sizing agent is applied, the solution is adjusted to slightly acidic pH in order to catalyze the reaction between epoxy and alkoxy silane. Amine silane does not require pretreatment due to its basic nature, which leads to self-catalyzation. An anhydride silane is insoluble in water, so ethanol was employed as solvent.

After the dissolution of the siloxanes in the respective solvent, the solution is kept for a certain period to form the silanol. Subsequently, the silane solutions were applied to the passivated Al powder in ethanol and allowed to react for several hours. The solvent was removed and the functionalized aluminium powder was washed with ethanol and dried. The dried powder was compounded with polyamide-6, and the mechanical properties were determined. The results are summarized in Table 4.

KH550 is (3-aminopropyl)triethoxysilane, molecular weight: 221.369.

KH560 is 3-glycidoxypropyltrimethoxysilane, molecular weight: 236.338. Table 4. Mechanical performance of PA 6 with 40 wt% of Al particle

Filler Tensile modulus Tensile strength Strain at break Charpy unnotched

(40 wt%) (MPa) (MPa) (%) (kJ/m²)

Passivated Al 8020±36 90.5±3.2 1.7±0.2 28.2±4.6

Passivated Al

7630±20 102.0±0.8 4.1±0.3 64.31 ±3.3 with KH550

Passivated Al

7810±8 102±1.2 4.25±0.3 60.3±7.4 with MAH

Passivated Al

7900±21 99.8±0.9 3.2±0.2 49.6±5.3 with KH560

The sizing of the aluminum improved the strain at break and charpy impact strength.

Example 5

In addition to the passivated aluminium flakes of Example 1 , spherical MgO, carbon black (CB) or h-BN were added. The thermal conductivity in-plane and through-plane was determined. The results are shown in Table 5.

Table 5. Hybrid with MgO, carbon black, and h-BN

Remarks: Test specimens were obtained from mini-extrusion and injection molding.

Further results are shown in the following Table 6. Table 6. Thermal conductivity of hybrid filler system

Component 2 3 4

PA 6 40 40 40 h-BN 50 30 20 Al flake 20 20 Al spherical 20 MgO 10 10

TC in-plane (W/mK) 8.3 5.7 6

TC through-plane (W/mK) 0.99 0.96 0.98

Remarks: Test specimens were obtained from ZSK18 extruder.

Claims

1. The use of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thickness of 1 to 200 nm as thermally conductive filler in organic polymers or precursors of organic polymers.

2. The use as claimed in claim 1, wherein the aluminium particles have an average particle size of from 5 to 100 pm, preferably of from 10 to 50 pm.

3. The use according to claim 1 or 2, wherein the aluminium particles are or comprise alu minium flakes.

4. The use as claimed in one of claims 1 to 3, wherein the surface coated aluminium parti cles are furthermore surface-functionalized with a silane coupling agent.

5. A method for increasing the chemical stability of organic polymers or precursors of organic polymers filled with aluminium particles, involving the step of adding aluminium particles having an average particle size of from 1 to 150 pm which are surface coated with an S1O2 layer having a layer thickness of 1 to 200 nm to the organic polymers or precursors of or ganic polymers.

6. The method as claimed in claim 5, wherein the aluminium particles are or comprise alu minium flakes.

7. A thermoplastic molding composition comprising a) from 5 to 99% by weight of at least one thermoplastic polymer as component A, b) from 1 to 90% by weight of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thick ness of 1 to 200 nm as component B, c) from 0 to 60% by weight of at least one fibrous or particulate filler which is different from component B, as component C, d) from 0 to 50% by weight of further additives, as component D, where the total of the percentages by weight of components A to D is 100% by weight.

8. The thermoplastic molding composition as claimed in claim 7, wherein component B, the aluminium particles, have an average particle size of from 5 to 100 pm, preferably of from 10 to 50 pm.

9. The thermoplastic molding composition as claimed in claim 7 or 8, wherein component B, the aluminium particles, are or comprise aluminium flakes.

10. The thermoplastic molding composition as claimed in one of claims 7 to 9, wherein the surface-coated aluminium particles of component B are furthermore surface-functionalized with a silane coupling agent.

11. The thermoplastic molding composition as claimed in one of claims 7 to 10, wherein com ponent A is selected from polyamide, polyester, polycarbonate, styrene polymer, polyure thane, polyolefin, polyketone, polylactide, polyphenylene sulfide, polyimide, epoxy resin, silicone resin, preferably from polyamide, polyester, polycarbonate, styrene polymer, poly urethane, polyolefin, polyketone and mixtures thereof.

12. The thermoplastic molding composition as claimed in one of claims 7 to 11 , wherein com ponent C comprises 1 to 25% by weight, based on the total of percentages by weight of components A to D which is 100% by weight, of a particulate ceramic filler, preferably spherical MgO.

13. A polyol composition for producing polyurethanes, comprising a’) from 5 to 99% by weight of at least one polyol, as component A’, b’) from 1 to 90% by weight of aluminium particles having an average particle size of from 1 to 150 pm which are surface-coated with an S1O2 layer having a layer thick ness of 1 to 200 nm, as component B’, c’) from 0 to 30% by weight of further additives, as component C’, where the total of the percentages by weight of components A’ to C’ is 100% by weight.

14. A process for preparing the thermoplastic molding composition as claimed in one of claims 7 to 12 or the polyol composition as claimed in claim 13 by mixing the ingredients.

15. The use of the thermoplastic molding composition as claimed in one of claims 7 to 12 or of the polyol composition of claim 13 for forming moldings.

16. A molding made of a thermoplastic molding composition as claimed in one of claims 7 to 12 or of a polyurethane reactive system comprising the polyol composition as claimed in claim 13 and an isocyanate component.