WO2015132707A1

WO2015132707A1 - Core-shell particles comprising low bulk density carbon in the shell

Info

Publication number: WO2015132707A1
Application number: PCT/IB2015/051511
Authority: WO
Inventors: Matthias Georg SCHWAB; Torsten WOMBACHER; Robert Bayer; Hye Jin Park; Cecile Schneider; Zeljko Tomovic; Xin Yang; Jon Powell
Original assignee: Basf Se; Basf (China) Company Limited
Priority date: 2014-03-04
Filing date: 2015-03-02
Publication date: 2015-09-11
Also published as: TW201536853A

Abstract

Core-shell particles comprising low bulk density carbon, especially graphene, in the shell are disclosed, also disclosed is a method for producing such core-shell particles, a method for preparing a polymer containing low bulk density carbon, especially graphene, a polymer obtainable by this method and the use of this polymer as or for producing a gas barrier material, an electrically conductive material, a thermally conductive material or a mechanically reinforced material.

Description

Core-shell particles comprising low bulk density carbon in the shell

Description The present invention relates to core-shell particles comprising low bulk density carbon, especially graphene, in the shell, to a method for producing such core-shell particles, to a method for preparing polymers containing low bulk density carbon, especially graphene, to polymers obtainable by this method and to the use of these polymers as or for producing a gas barrier material, an electrically conductive material, a thermally conductive material or a mechanically reinforced material.

Polymer composites containing carbon are very interesting materials as they have a number of useful properties. They are mechanically reinforced, possess gas barrier properties and are electrically and/or thermally conductive. Their preparation encounters however substantial difficulties, as the most interesting carbon materials, such as graphene, carbon nanotubes or specific graphite or carbon black types, are characterized by a very low bulk density of mostly below 0.2g/cm³ or even below 0.1 g/cm³, which makes them very difficult to process. For instance, this "fluffiness" makes a defined addition of a sufficient amount into a continuous process, such as extrusion, extremely difficult. A thorough dispersion of carbon in the polymer, which is a prerequisite for obtaining the desired properties, is also very difficult to obtain, even in bulk processes.

K. Kalaitzidou et al. describe in Composites Science and Technology 2007, 67, 2045- 2051 a method for producing exfoliated graphite-polypropylene nanocomposites. For this purpose, polypropylene is coated with exfoliated graphite nanoplatelets either in a melt mixing process or via mixing a suspension of exfoliated graphite nanoplatelets in xylene with a solution of polypropylene in xylene and isolating the coated

polypropylene or via dispersing exfoliated graphite nanoplatelets in isopropanol by sonication, adding polypropylene powder and finally removing the solvent. The compounding products obtained by either way are then subjected to compression or injection molding to give the composites. The melt mixing process results however in a dissatisfactory dispersion of graphite in the polymer. The dissolution alternative in xylene requires high amounts of solvent and also high temperatures for dissolving the polymer. The third alternative in which exfoliated graphite nanoplatelets are dispersed in isopropanol has the disadvantage that the amount of graphene dispersed in polypropylene is limited by the viscosity of the isopropanol dispersion, which increases enormously when the amount of graphene exceeds a certain value. Increasing the amount of isopropanol is not an economic solution for this problem as the solvent must eventually be removed.

H. Kim et al. describe in Chemistry of Materials 2010, 22, 3441 -3450 the preparation of thermoplastic polyurethane reinforced with exfoliated graphite via melt compounding, solvent blending or in situ polymerization. Melt compounding results in a less effective distribution of the exfoliated sheets in the polymer matrix. Distribution obtained in the solvent blend process is better, but slow solvent evaporation is said to induce reagglomeration of the graphitic particles. Moreover, the use of sufficiently large amounts of solvent is cost-intensive and to be avoided from an environmental aspect. The properties of composites obtained via in situ polymerization were not as good as expected.

Similarly, H. Kim et al. discuss in Macromolecules 2010, 43, 6515-6530 solvent- and melt-based strategies for dispersing reduced graphene oxide in polymers.

The object of the present invention was to provide a method for producing polymer composites containing low bulk density carbon which solves the above described dosage or metering as well as distribution problems of carbon and allows the production of composites containing low bulk density carbon in virtually any

discretionary amount and in a well-dispersed manner. Moreover, it should be possible to carry out the method as a continuous process.

The problem is solved by core-shell particles comprising in the shell low bulk density carbon. These core-shell particles can be used as a masterbatch in the production of polymer composites containing low bulk density carbon.

In a first aspect, the present invention relates to core-shell particles, where the core comprises a polymer A; and the shell comprises a polymer B and low bulk density carbon; where polymers A and B can be the same or different.

In terms of the present invention, "low bulk density carbon" is a carbon material having a bulk density of at most 0.2 g/cm³, e.g. from 0.001 to 0.2 g/cm³ or from 0.003 to 0.2 g/cm³, preferably of at most 0.15 g/cm³, e.g. from 0.001 to 0.15 g/cm³ or from 0.003 to 0.15 g/cm³, more preferably of at most 0.1 g/cm³, e.g. from 0.001 to 0.1 g/cm³ or from 0.003 to 0.1 g/cm³, in particular of at most 0.05 g/cm³, e.g. from 0.001 to 0.05 g/cm³ or from 0.003 to 0.05 g/cm³, and specifically of at most 0.01 g/cm³, e.g. from 0.001 to 0.01 g/cm³ or from 0.003 to 0.01 g/cm³. The specification of the bulk density of the carbon material of course relates to the bulk density of the carbon starting material as used in the production of the core-shell particles of the invention.

The bulk density of a powder is the ratio of the mass of an untapped powder sample and its volume including the contribution of the interparticulate void volume. Hence, the bulk density depends on both the density of powder particles and the spatial arrangement of particles in the powder bed. In general, the bulk density of a powder is determined by measuring the volume of a known mass of powder sample, that may have been passed through a sieve, into a graduated cylinder (Method A), or by measuring the mass of a known volume of powder that has been passed through a volumeter into a cup (Method B) or a measuring vessel (Method C). In terms of the present invention, the values given for the bulk density of the carbon material are determined by method A. To this purpose, a 100 ml graduated glass (e.g. borosilicate) cylinder is placed on a precision balance and tared. A powder funnel (e.g. of Duran glass) is placed on the cylinder and the material of which the bulk density is to be determined is filled steadily into the cylinder up to a volume between 90 and 100 ml. If agglomerates are observed during the process of filling, the material is first passed through a sieve of 0.1 mm mesh. The powder funnel is removed and the material is allowed to continue to flow for 30 seconds. Then the exact volume and the weight of the material are determined. The bulk density is calculated from the quotient of determined mass and volume (pb = m/V [g/ml]).

The low bulk density carbon material is mainly composed of carbon, but it may contain minor amounts, for example up to 20% by weight or up to 10% by weight, of further elements, such as hydrogen, oxygen, nitrogen, sulfur and metals (also in the form of metal oxides; metals and metal oxides mostly originating from the production process of the low bulk density carbon material), based on the total weight of the material. In a particular embodiment, the low bulk density carbon material is nano-scaled carbon (also termed nano carbon). In terms of the present invention, this is a carbon material composed of particles of which at least one dimension, preferably one dimension, is at most 1 pm, preferably at most 500 nm, more preferably at most 250 nm, even more preferably at most 200 nm, particularly preferably at most 100 nm, in particular at most 50 nm and specifically at most 20 nm. The lower limit of the size of this dimension is limited by the thickness of a single layer, which is ca. 0.3 nm. Preferably, the low bulk density carbon material is selected from graphene, carbon nanotubes, fullerenes, low bulk density carbon black, low bulk density graphite and mixtures thereof. Graphene is a monolayer of carbon atoms arranged in a two-dimensional honeycomb network. "Graphene" in the terms of the present invention is however not restricted to a material consisting exclusively of single-layer graphene (i.e. graphene in the proper sense and according to the lUPAC definition), but, like in many publications and as used by most commercial providers, rather denotes a bulk material, which is generally a mixture of a single-layer material, a bi-layer material and a material containing 3 to 10 layers and sometimes even more than 20 layers ("few layer graphene"). The ratio of the different materials (single, bi and multiple layers) depends on the production process and provider. In case of the present invention, the material termed "graphene" is characterized by the absence of the graphite peak in the XRD: The degree of exfoliation of the graphene material being related to the layer thickness can be monitored by XRD (X-ray diffraction). The presence of the reflection at 2theta = 25 to 30 ° (with Cu Ka radiation, X-ray wavelength = 0.154 nm; the precise value is 26.3°, but often only a broad band instead of a sharp peak is obtained) originates from the layered structure and thus relates to the amount of native graphite. Preferably, the graphene of the invention does not reveal a graphite peak related to the stacking and thus unexfoliated material.

"Graphene" in terms of the present invention is further characterized by a low bulk density of at most 0.2 g/cm³, e.g. from 0.001 to 0.2 g/cm³ or from 0.003 to 0.2 g/cm³, preferably at most 0.15 g/cm³, e.g. from 0.001 to 0.15 g/cm³ or from 0.003 to 0.15 g/cm³, more preferably at most 0.1 g/cm³, e.g. from 0.001 to 0.1 g/cm³ or from 0.003 to 0.1 g/cm³, in particular at most 0.05 g/cm³, e.g. from 0.001 to 0.05 g/cm³ or from 0.003 to 0.05 g/cm³, and specifically at most 0.01 g/cm³, e.g. from 0.001 to 0.01 g/cm³ or from 0.003 to 0.01 g/cm³.

"Graphene" in terms of the present invention is moreover characterized by a high BET (Brunauer-Emmett-Teller) surface are. Preferably, the BET area is at least 200 m²/g, e.g. from 200 to 2600 or from 200 to 2000 or from 200 to 1500 m²/g or from 200 to 700 m²/g; more preferably at least 300 m²/g, e.g. from 300 to 2600 or from 300 to 2000 or from 300 to 1500 or from 300 to 700 m²/g.

"Graphene" is preferably characterized by a high ratio of carbon to oxygen atoms (C/O ratio): The elemental composition as expressed by the ratio of carbon to oxygen atoms (C/O ratio) is related to the degree of chemical reduction of the graphene material. The C/O ratio is preferably at least 3:1 , more preferably at least 5:1 , even more preferably at least 50:1 , particularly preferably at least 100:1 and in particular at least 500:1 , as determined e. g. from the atomic percentages (at%) of the elements via X-ray photoelectron spectroscopy (XPS).

By way of example, suitable graphene materials and methods for preparing them are described in Macromolecules 2010, 43, pages 6515 to 6530, in WO 2009/126592, J. Phys. Chem. B 2006, 1 10, 8535-8539, Chem. Mater. 2007, 19, 4396-4404 and in the literature cited therein.

Graphite is composed of stacked graphene sheets of linked hexagonal rings. In contrast to graphene, graphite in terms of the present invention is characterized by an essentially higher content of 20 and more layers than graphene. Contrary to graphene, it is characterized by the presence of the graphite peak in the XRD at 2theta = 25 to 30° (see above remarks). In any case, graphite to be used according to the present invention is characterized by a very low bulk density of at most 0.2 g/cm³, e.g. from 0.001 to 0.2 g/cm³ or from 0.003 to 0.2 g/cm³, preferably by a bulk density of at most 0.15 g/cm³, e.g. from 0.001 to 0.15 g/cm³ or from 0.003 to 0.15 g/cm³, more preferably at most 0.1 g/cm³, e.g. from 0.001 to 0.1 g/cm³ or from 0.003 to 0.1 g/cm³, in particular at most 0.05 g/cm³, e.g. from 0.001 to 0.05 g/cm³ or from 0.003 to 0.05 g/cm³, and specifically at most 0.01 g/cm³, e.g. from 0.001 to 0.01 g/cm³ or from 0.003 to 0.01 g/cm³.

Fullerenes are allotropes of carbon in the form of a hollow sphere, ellipsoid or tube. Spherical fullerenes are also called buckyballs; cylindrical ones are called carbon nanotubes or buckytubes. Fullerenes are similar in structure to graphite, which is composed of stacked graphene sheets of linked hexagonal rings; but they may also contain pentagonal (or sometimes heptagonal) rings. In the present invention, the term "fullerenes" is limited to spherical forms; the cylindrical ones being separately treated as nanotubes.

As mentioned above, carbon nanotubes (CNT's) are allotropes of carbon with a cylindrical nanostructure and are members of the fullerene structural family. Their name is derived from their long, hollow structure with the walls formed by one-atom- thick sheets of carbon (they can be illustrated as graphene tubes). These sheets are rolled at specific and discrete ("chiral") angles, and the combination of the rolling angle and radius decides the nanotube properties; for example, whether the individual nanotube shell is a metal or semiconductor. Nanotubes are categorized as single- walled nanotubes (SWCNTs) and multi-walled nanotubes (MWCNTs). Individual nanotubes naturally align themselves into "ropes" held together by van der Waals forces, more specifically, π-stacking. CNT's have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. In particular, owing to their extraordinary thermal conductivity and mechanical and electrical properties, carbon nanotubes find applications as additives to various structural materials. Nanotubes, and also the synthesis thereof, are described, for example, in J. Hu et al., Acc. Chem. Res. 32 (1999), 435-445. Suitable CNTs are described, for example, in DE-A-102 43 592, EP-A-2 049 597, DE-A-102 59 498, WO 2006/026691 and WO 2009/000408. It is preferable that the diameter of the individual tubes is from 4 to 20 nm, in particular from 5 to 10 nm. The exterior shape of the tubes can moreover vary and can have uniform internal and external diameter, but it is also possible to produce tubes in the shape of a knot and to produce vermicular structures. The aspect ratio (length of respective graphite tube in relation to its diameter) is at least 10, preferably at least 5. The length of the nanotubes is at least 10 nm.

Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio. It is produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil. Carbon black is preferably a conductive carbon black. Any familiar form of carbon black can be used as conductive carbon black as long as it fulfills the mentioned bulk density criterion, and by way of example the commercially available products Ketjenblack® EC- 600JD from AkzoNobel (bulk density: 0.1 -0.12 g/cm³) or Printex® XE2-B from Orion Engineered Carbons (bulk density: ca. 0.13 g/cm³) are suitable. Carbon black conducts electrons by virtue of graphite-type layers embedded within amorphous carbon. The current is conducted within the aggregates made of carbon black particles and between the aggregates, if the distances between the aggregates are sufficiently small. In order to achieve conductivity while minimizing the amount added, it is preferable to use carbon black having anisotropic structure. In this carbon black, the primary particles form aggregates giving anisotropic structures, and the necessary distances between the carbon black particles for achieving conductivity in compounded materials are therefore achieved even at comparatively low loading. In any case, carbon black to be used according to the present invention is characterized by a very low bulk density of at most 0.2 g/cm³, e.g. from 0.001 to 0.2 g/cm³ or from 0.003 to 0.2 g/cm³, preferably by a bulk density of at most 0.15 g/cm³, e.g. from 0.001 to 0.15 g/cm³ or from 0.003 to 0.15 g/cm³, and more preferably at most 0.13 g/cm³, e.g. from 0.001 to 0.13 g/cm³ or from 0.003 to 0.13 g/cm³. Suitable carbon blacks are for example described in D. Pantea et al., Applied Surface Science 2003, 217, 181 -193. Among the above-listed low bulk density carbon materials, preference is given to graphene, CNT's, low bulk density graphite and low bulk density carbon black, more preference to graphene and CNT's, and in particular to graphene. In the core-shell particles, the shell preferably contains 0.1 to 99.9%, more preferably 0.5 to 75% by weight, even more preferably 1 to 50% by weight, in particular 5 to 30% by weight and especially 5 to 15% by weight of low bulk density carbon, based on the total weight of polymer B and the low bulk density carbon. The content of low bulk density carbon in the core-shell particles depends strongly on the size and density of the core and can be varied within wide ranges. In a preferred embodiment, the core-shell particles contain 0.01 to 25% by weight, more preferably 0.1 to 15%, and in particular 1 to 5% by weight of low bulk density carbon, based on the total weight of the particles.

The size of the core-shell particles is not critical and can vary within wide ranges.

Preferably, their longest dimension is from 100 μιτι to 5 cm, more preferably from 1 mm to 3 cm, in particular from 2 mm to 1 cm and specifically from 3 mm to 7 mm. In case of spherical particles, this "longest dimension" corresponds of course to the diameter and in cubic particles to the unitary space diagonal.

The shape of the core-shell particles is not critical either, and can take any conceivable form. For practical reasons, however, especially in view of the production process, they are preferably rather round-shaped, for example spherical, oblong or lentil-shaped, or cubic, and in particular round-shaped.

Polymers A and B are preferably selected from thermoplastics and thermoplastic elastomers. Thermoplastics are plastics which yield solid materials upon cooling of a polymer melt and soften upon heating, the shaping of a thermoplastic thus being a reversible process. They are normally composed of relatively high molar mass molecules and form the major part of plastics. Examples are vinylaromatic polymers, like polystyrene (including high impact polystyrene), acrylonitrile/butadiene/styrene (ABS) and styrene/acrylonitrile polymers (SAN); poly(phenylene oxide) (PPO), PPO-polyamide alloys, polyethersulfones (PESU), polysulfones (PSU), polyphenylsulfones (PPSU; PPSF), polyetherketones (PEK), polyetheretherketones (PEEK), polyolefins, ethylene/vinyl alcohol (EVOH) copolymers, polyimides, polyacetals, like

polyoxymethylenes (POM); polyetherimides, fluoropolymers, fluorinated ethylene propylene polymers (FEP), polyvinyl fluoride), poly(vinylidene fluoride), poly(vinylidene chloride), polyvinyl chloride), poly(acrylonitrile), polycarbonates (PC), polyamides, thermoplastic polyurethanes (TPU), polyesters, such as poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), poly(1 ,3-propylene terephthalate) (PPT), poly(ethylene naphthalate) (PEN), and poly(cyclohexanedimethanol terephthalate) (PCT); and liquid crystalline polymers (LCP).

Preferred thermoplastics are polyolefins, vinylaromatic polymers, polyamides, polyesters, polyacetals, polycarbonates, thermoplastic polyurethanes (TPU), polyethersulfones, polysulfones, polyphenylsulfones and ionomers. More preference is given to polyolefins, polyamides, polyacetals (especially POM) and thermoplastic polyurethanes (TPU) and specifically to polyolefins, polyamides and thermoplastic polyurethanes (TPU). Polyolefins:

For the purposes of the present invention the term "polyolefin" comprises all polymers composed of olefins without further functionality, such as polyethylene, polypropylene, polybut-1 -ene or polyisobutylene, poly-4-methylpent-1 -ene, polyisoprene, poly- butadiene, polymers of cycloolefins, such as of cyclopentene or norbornene, and also copolymers of monoolefins or diolefins, such as ethylene-propylene copolymers or ethylene-butadiene-copolymers.

Ethylene polymers:

Suitable polyethylene (PE) homopolymers, classed according to density, are for example:

PE-ULD (U LD = ultralow density), PE-VLD (VLD = very low density); copolymers and terpolymers of ethylene with up to 10% octene, 4-methylpent-1 -ene, and occasionally propylene; density between 0.91 and 0.88 g/cm³; barely crystalline, transparent

- PE-LD (LD = low density), obtainable, for example, by the high-pressure process (ICI) at 1000 to 3000 bar and 150 to 300°C with oxygen or peroxides as catalysts in autoclaves or tube reactors. Highly branched with branches of different length, crystallinity 40 to 50%, density 0.915 to 0.935 g/cm³, average molar mass up to 600 000 g/mol.

- PE-LLD (LLD = linear low density), obtainable with metal complex catalysts in the low-pressure process from the gas phase, from a solution (e.g., benzine), in a suspension or with a modified high-pressure process. Slight branching with side chains which are themselves unbranched, molar masses higher than for PE-LD. PE-MD (MD = middle density); the density between 0.93 and 0.94 g/cm³; can be prepared by mixing PE-LD and PE-H D or directly as a copolymeric PE-LLD. PE-HD (HD = high density), obtainable by the medium-pressure (Phillips) and low-pressure (Ziegler) processes. By Phillips at 30 to 40 bar, 85 to 180°C, chromium oxide catalyst, molar masses about 50 000 g/mol. By Ziegler at 1 to 50 bar, 20 to 150°C, titanium halides, titanium esters or aluminum alkyls as catalysts, molar mass about 200 000 to 400 000 g/mol. Execution in suspension, solution, gas phase or bulk. Very slight branching, crystallinity 60% to 80%, density 0.942 to 0.965 g/cm³.

PE-HD-HMW (HMW = high molecular weight), obtainable by Ziegler, Phillips or gas-phase method. High density and high molar mass.

PE-HD-UHMW (UHMW = ultra high molecular weight) obtainable with modified Ziegler catalyst, molar mass 3 000 000 to 6 000 000 g/mol.

Suitable ethylene copolymers are all commercial ethylene copolymers, examples being Luflexen® grades (LyondellBasell), Nordel® and Engage® (The Dow Chemical

Company). Examples of suitable comonomers include a-olefins having 3 to 10 carbon atoms, especially propylene, but-1-ene, hex-1 -ene, 4-methylpent-1 -ene, hept-1 -ene and oct-1 -ene, and also alkyl acrylates and methacrylates having 1 to 20 carbon atoms in the alkyl radical, especially butyl acrylate. Further suitable comonomers are dienes such as butadiene, isoprene, and octadiene, for example. Further suitable

comonomers are cycloolefins, such as cyclopentene, norbornene, and

dicyclopentadiene.

The ethylene copolymers are typically random copolymers or block or impact copolymers. Suitable block or impact copolymers of ethylene and comonomers are, for example, polymers for which in the first stage a homopolymer of the comonomer or a random copolymer of the comonomer is prepared, containing up to 15% by weight of ethylene, and then in the second stage a comonomer-ethylene copolymer with ethylene contents of 15% to 80% by weight is polymerized on. Ordinarily, sufficient of the comonomer-ethylene copolymer is polymerized on for the copolymer produced in the second stage to have a fraction of 3% to 60% by weight in the end product.

Propylene polymers:

Polypropylene should be understood below to refer both to homopolymers and to copolymers of propylene. Copolymers of propylene comprise minor amounts of monomers copolymerizable with propylene, examples being C2-Cs-alk-1 -enes such as ethylene, but-1 -ene, isobutene, pent-1 -ene or hex-1 -ene, among others, and dienes, such as butadiene. It is also possible to use two or more different comonomers. Suitable polypropylenes include homopolymers of propylene or copolymers of propylene with up to 50% by weight of copolymehzed other alk-1 -enes having up to 8 C atoms. The copolymers of propylene are in this case random copolymers or block or impact copolymers. Where the copolymers of propylene are of random construction they generally comprise up to 15% by weight, preferably up to 6% by weight, of other alk-1 -enes having up to 8 C atoms, especially ethylene, but-1 -ene or a mixture of ethylene and but-1 -ene.

Other polyolefins

Other suitable polyolefins are homopolymers of higher alkenes or dienes, such as but-1 -ene, isobutylene, 4-methyl-1-pentene, butadiene or isoprene, and copolymers thereof, such as isobutylene/isoprene copolymers.

Other olefin copolymers

The polyolefin may also be selected from copolymers of mono-olefins or diolefins with vinyl monomers and mixtures thereof. These include, for example, ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylate copolymers, ethylene/vinyl acetate copolymers, and copolymers thereof with carbon monoxide, or ethylene/acrylic acid copolymers and their salts (ionomers).

Vinylaromatic polymers

Vinyl-aromatic monomers used to prepare the vinyl aromatic polymers include styrene, a-methylstyrene, all isomers of vinyltoluene, ethylstyrene, butylstyrene, dimethylstyrene and mixtures thereof. In addition, the vinyl aromatic monomers mentioned above can be copolymerized with other copolymerizable monomers. Examples of these monomers are (meth)acrylic acid, C1-C4 alkyl esters of (meth)acrylic acid, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, butyl acrylate, amides and nitriles of (meth)acrylic acid such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, butadiene, ethylene, divinylbenzene, maleic anhydride, phenylmaleinimide and the like. Preferred copolymerizable monomers are acrylonitrile, butadiene, (meth)acrylic acid, (meth)acrylates, maleic anhydride and phenylmaleinimide, in particular acrylonitrile, butadiene, (meth)acrylic acid and (meth)acrylates. Specific examples for vinylaromatic polymers include polystyrene, poly(p-methylstyrene) and poly(a-methylstyrene). Specific examples for vinylaromatic polymers also include copolymers of styrene or a-methylstyrene with dienes or acrylic derivatives, or graft copolymers of styrene or α-methylstyrene such styrene-arcrylonitrile copolymers, a-methylstyrene-acrylonitrile copolymers, styrene- maleicanhydride copolymers, styrene-phenylmaleinimide copolymers,

methylmethacrylate-copolymere, styene-methylmethacrylate-acrylonitrile-copolymers, styrene-acrylonitrile-maleic anhydride-copolymers, styrene-acrylonitrile- phenylmaleinimide-copolymers, a-methylstyrene-acrylonitrile-methyl methacrylate- copolymers, a-methylstyrene-acrylonitrile-t-butyl methacrylate-copolymers, styrene- acrylonitrile-t-butyl methacrylate-copolymers, preferably acrylonitrile styrene acrylate copolymers (ASA), acrylonitrile butadiene styrole copolymers (ABS) and styrene acrylonitrile copolymers (SAN).

Polyamides

Polyamides (abbreviated code PA) have as key structural elements amide groups in the main polymer chain. Polyamide polymers are herein to be understood as being homopolymers, copolymers, blends and grafts of synthetic long-chain polyamides having recurring amide groups in the polymer main chain as an essential constituent. Polyamides can be prepared, for example, by polycondensation from diamines and dicarboxylic acids or their derivatives, such as aminocarbonitriles, aminocarboxamides, aminocarboxylate esters or aminocarboxylate salts. Examples of suitable diamines include alkyldiamines such as C2-C2o-alkyldiamines, e.g., hexamethylenediamine, or aromatic diamines, such as C6-C2o-aromatic diamines, e.g., m-, o- or p- phenylenediamine or m-xylenediamine. Suitable dicarboxylic acids comprise aliphatic dicarboxylic acids or their derivatives, chlorides for example, such as C2-C2o-aliphatic dicarboxylic acids, e.g., sebacic acid, decanedicarboxylic acid or adipic acid, or aromatic dicarboxylic acids, examples being C6-C2o-aromatic dicarboxylic acids or their derivatives, chlorides for example, such as 2,6-naphthalenedicarboxylic acid, isophthalic acid or terephthalic acid. Examples of polyamides of this kind are poly- 2,4,4-trimethylhexamethyleneterephthalamide or poly-m-phenyleneisophthalamide, PA 66 (nylon-6,6; polyhexamethyleneadipamide), PA 46 (nylon-4,6;

polytetramethyleneadipamide), PA 69 (nylon-6,9; polycondensation product of

1 ,6-hexamethylenediamine and azelaic acid), PA 610 (nylon-6,10;

polyhexamethylenesebacamide; polycondensation product of 1 ,6-hexamethylene diamine and 1 ,10-decanedioic acid), PA 612 (nylon-6,12; polycondensation product of 1 ,6-hexamethylenediamine and 1 , 12-dodecanedioic acid), PA 1010 (nylon 10,10; polycondensation product of 1 ,10-decamethylenediamine and 1 ,10-decanedicarboxylic acid), PA 1012 (polycondensation product of 1 ,10-decamethylenediamine and dodecanedicarboxylic acid) or PA 1212 (polycondensation product of 1 ,12-dodeca- methylenediamine and dodecanedicarboxylic acid); the first number in each case indicating the number of carbon atoms in the diamine and the second number the number of carbon atoms in the dicarboxylic acid. Further examples are PA 6T

(polycondensation product of hexamethylenediamine and terephthalic acid) and PA 9T (polycondensation product of nonamethylenediamine and terephthalic acid). Polyamides are likewise obtainable by polycondensation from amino acids, examples being C2-C2o-amino acids such as 6-aminocaproic acid, 1 1 -aminoundecanoic acid or by ring-opening polymerization from lactams, ε-caprolactam being the most prominent example. Examples of polyamides of this kind are PA 4 (synthesized from

4-aminobutyric acid), PA 6 (nylon-6; polycaprolactam; synthesized from ε-caprolactam or 6-aminohexanoic acid), PA 7 (nylon-7; polyenantholactam or polyheptanoamide), PA 10 (nylon-10, polydecanoamide) PA 1 1 (nylon-1 1 ; polyundecanolactam), PA 12 (nylon- 12; polydodecanolactam). In the case of polyamides which, as in this case, are synthesized only from one monomer, the number after the abbreviation PA indicates the number of carbon atoms in the monomer.

Polyamide copolymers may comprise the polyamide building blocks in various ratios. Examples of polyamide copolymers are nylon 6/66 and nylon 66/6 (PA 6/66, PA 66/6, copolyamides made from PA 6 and PA 66 building blocks, i.e. made from caprolactam, hexamethylenediamine and adipic acid). PA 66/6 (90/10) may contain 90% of PA 66 and 10% of PA 6. Further examples are PA 66/610 (nylon-66/610, made from hexamethylenediamine, adipic acid and sebacic acid) and PA 6/66/136

(polycondensation product of caprolactam, hexamethyleneaminadipate and

4,4-diaminodicyclohexylmethanadipate).

Polyamides further include partially aromatic polyamides. The partially aromatic polyamides are usually derived from aromatic dicarboxylic acids such as terephthalic acid or isophthalic acid and a linear or branched aliphatic diamine. Examples are PA 9T (formed from terephthalic acid and nonanediamine), PA 6T/6I (formed from hexamethylenediamine, terephthalic acid and isophthalic acid), PA 6T/6, PA 6T/6I/66 and PA 6T/66.

Polyamides further include aromatic polyamides such as poly-meta-phenylene- isophathalamides (Nomex®) or poly-para-phenylene-terephthalamide (Kevlar®).

Polyamides further include copolymers made of polyamides and of a further segment, for example taking the form of a diol, polyester, ether, etc., in particular in the form of polyesteramides, polyetheresteramides or polyetheramides. For example, in polyetheramides, the polyamide segment can be any commercial available polyamide, preferably PA 6 or PA 66 and the polyether is usually polyethylene glycol,

polypropylene glycol or polytetramethylene glycol.

Polyamides can if appropriate be prepared with an elastomer as modifier. Examples of suitable copolyamides are block copolymers of the aforementioned polyamides with polyolefins, olefin copolymers, ionomers or chemically bonded or grafted elastomers; or with polyethers, such as with polyethylene glycol, polypropylene glycol or polytetra- methylene glycol. Also suitable are EPDM- or ABS-modified polyamides or

copolyamides, and polyamides condensed during processing (RIM polyamide systems).

Polyesters

Suitable polyesters and copolyesters are described, for example, in EP-A-0678376, EP-A-0 595 413, and US 6,096,854. Polyesters are condensation products of one or more polyols and one or more polycarboxylic acids or the corresponding lactones. In linear polyesters, the polyol is a diol and the polycarboxylic acid a dicarboxylic acid. The diol component may be selected from ethylene glycol, 1 ,4-cyclohexanedimethanol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,4-butanediol, 2,2-dimethyl-1 ,3-propanediol, 1 ,6-hexanediol, 1 ,2-cyclohexanediol, 1 ,4-cyclohexanediol, 1 ,2-cyclohexanedimethanol, and 1 ,3-cyclohexanedimethanol. Also suitable are diols whose alkylene chain is interrupted one or more times by nonadjacent oxygen atoms. These include diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, and the like. In general the diol comprises 2 to 18 carbon atoms, preferably 2 to 8 carbon atoms. Cycloaliphatic diols can be used in the form of their cis or trans isomers or as an isomer mixture. The acid component may be an aliphatic, alicyclic or aromatic dicarboxylic acid. The acid component of linear polyesters is generally selected from terephthalic acid, isophthalic acid, 1 ,4-cyclohexanedicarboxylic acid, 1 ,3-cyclohexanedicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, 1 ,12-dodecanedioic acid,

2,6-naphthalenedicarboxylic acid, and mixtures thereof. It will be appreciated that the functional derivatives of the acid component can also be employed, such as esters, examples being the methyl esters, or anhydrides or halides, preferably chlorides.

Preferred polyesters are polyalkylene terephthalates, and polyalkylene naphthalates, which are obtainable by condensing terephthalic acid or naphthalenedicarboxylic acid, respectively, with an aliphatic diol.

Preferred polyalkylene terephthalates are polyethylene terephthalates (PET), which are obtained by condensing terephthalic acid with diethylene glycol. PET is also obtainable by transesterifying dimethyl terephthalate with ethylene glycol, with elimination of methanol, to form bis(2-hydroxyethyl) terephthalate, and subjecting the product to polycondensation, releasing ethylene glycol. Further preferred polyesters are poly- butylene terephthalates (PBT), which are obtainable by condensing terephthalic acid with 1 ,4-butanediol, polyalkylene naphthalates (PAN) such as polyethylene

2,6-naphthalates (PEN), poly-1 ,4-cyclohexanedimethylene terephthalates (PCT), and also copolyesters of polyethylene terephthalate with cyclohexanedimethanol (PDCT), copolyesters of polybutylene terephthalate with cyclohexanedimethanol. Also preferred are copolymers, transesterification products, and physical mixtures (blends) of the aforementioned polyalkylene terephthalates. Particularly suitable polymers are selected from polycondensates and copolycondensates of terephthalic acid, such as poly- or copolyethylene terephthalate (PET or CoPET or PETG), poly(ethylene

2,6-naphthalate)s (PEN) or PEN/PET copolymers and PEN/PET blends. Said copolymers and blends, depending on their preparation process, may also comprise fractions of transesterification products.

Polyacetals

Polyacetals comprise both homopolymers as well as copolymers of polyacetals with cyclic ethers, and polyacetals modified with thermoplastic polyurethanes, acrylates or methyl acrylate/butadiene/styrene copolymers. Polyacetals are produced by the polymerization of aldehydes or of cyclic acetals. One industrially significant polyacetal is polyoxymethylene (POM), which is obtainable through cationic or anionic

polymerization of formaldehyde or trioxane, respectively. Modified POM is obtained, for example, by copolymerization with cyclic ethers such as ethylene oxide or

1 ,3-dioxolane. Combination of POM with thermoplastic polyurethane elastomers produces POM-based polymer blends. Unreinforced POM is notable for very high stiffness, strength, and toughness. POM is used preferably for constructing household appliances and for constructing apparatus, vehicles, and machinery, and in sanitary and installation engineering.

Polycarbonates

Polycarbonates are prepared, for example, through condensation of phosgene or carbonic esters such as diphenyl carbonate or dimethyl carbonate with dihydroxy compounds. Suitable dihydroxy compounds are aliphatic or aromatic dihydroxy compounds. As aromatic dihydroxy compounds mention may be made for example of bisphenols such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), tetraalkylbisphenol A, 4,4-(meta-phenylenediisopropyl)diphenol (bisphenol M), 4,4-(para-phenylene- diisopropyl)diphenol, 1 ,1 -bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (BP-TMC), 2,2-bis(4-hydroxyphenyl)-2-phenylethane, 1 ,1 -bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), and also, if appropriate, mixtures thereof. The polycarbonates may be branched by using small amounts of branching agents. Suitable branching agents include phloroglucinol, 4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)hept-2-ene, 4,6-dimethyl- 2,4,6-tri(4-hydroxyphenyl)heptane; 1 ,3,5-tri(4-hydroxyphenyl)benzene;

1 ,1 ,1 -tri(4-hydroxyphenyl)heptane; 1 ,3,5-tri(4-hydroxyphenyl)benzene;

1 ,1 ,1 -tri(4-hydroxyphenyl)ethane; tri(4-hydroxyphenyl)phenylmethane,

2,2-bis[4,4-bis(4-hydroxyphenyl)cyclohexyl]propane; 2,4-bis(4-hydroxyphenyl- isopropyl)phenol; 2,6-bis(2-hydroxy-5'-methylbenzyl)-4-methylphenol; 2-(4-hydroxy- phenyl )-2-(2,4-dihydroxyphenyl)propane;

hexa(4-(4-hydroxyphenylisopropyl)phenyl)ortho-terephthalic esters;

tetra(4-hydroxyphenyl)methane; tetra(4-(4-hydroxyphenylisopropyl)phenoxy)methane; a,a',a"-tris(4-hydroxyphenyl)-1 ,3,5-triisopropylbenzene; 2,4-dihydroxybenzoic acid; trimesic acid; cyanuric chloride; 3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-

2,3-dihydroindole, 1 ,4-bis(4',4"-dihydroxytriphenyl)methyl)benzene, and, in particular, 1 ,1 ,1 -tri(4-hydroxyphenyl)ethane and bis(3-methyl-4-hydroxyphenyl)-2-oxo-

2.3- dihydroindole. Examples of compounds suitable for chain termination include phenols such as phenol, alkylphenols such as cresol and 4-tert-butylphenol, chlorophenol, bromophenol, cumylphenol, or mixtures thereof. The fraction of chain terminators is generally 1 to 20 mol%, per mole of dihydroxy compound.

Thermoplastic polyurethanes (TPUs)

Polyurethanes are generally synthesized from at least one polyisocyanate and at least one compound having at least two groups per molecule that are reactive toward isocyanate groups.

Thermoplastic polyurethane is usually produced by reacting (a) organic and/or modified polyisocyanates with (b) at least one relatively high-molar-mass compound having hydrogen atoms reactive toward isocyanate, (c) if appropriate, low-molar-mass chain extenders in the presence of (d) a catalyst and, if desired, (e) one or more further additives.

The polyisocyanates (a) used can be selected from aliphatic, cycloaliphatic, araliphatic and aromatic diisocyanates and mixtures thereof. Preferred polyisocyanates are diisocyanates. Preferred aromatic and araliphatic polyisocyanates are selected from the following individual polyisocyanates: toluylene 2,4-diisocyanate, toluylene

2,6-diisocyanate, mixtures composed of toluylene 2,4- and 2,6-diisocyanate, diphenylmethane 4,4'-diisocyanate, diphenylmethane 2,4'-diisocyanate,

diphenylmethane 2,2'-diisocyanate, mixtures composed of diphenylmethane 2,4'- and 4,4'-diisocyanate, urethane-modified liquid diphenylmethane 4,4'- and/or

2.4- diisocyanates, 4,4'-diisocyanato-1 ,2-diphenylethane, naphthylene 1 ,5-diisocyanate and mixtures thereof. Suitable aliphatic and cycloaliphatic diisocyanates used are conventional aliphatic and/or cycloaliphatic diisocyanates. Preferably, they are selected from trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate,

octamethylene diisocyanate, 2-methylpentamethylene 1 ,5-diisocyanate,

2-ethylbutylene 1 ,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1 ,4- and/or

1 ,3-bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1 ,4-diisocyanate, 1 -methylcyclohexane 2,4-diisocyanate, 1 -methylcyclohexane 2,6-diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, dicyclohexylmethane 2,4'-diisocyanate, dicyclohexylmethane 2,2'-diisocyanate, tetramethylxylylene diisocyanate (MXDI) and mixtures thereof. MXDI is generally termed an aliphatic diisocyanate because the isocyanate groups are bound to the (aliphatic) CH2 groups. It is preferable that the polyisocyanate (a) used is selected from hexamethylene 1 ,6-diisocyanate

(hexamethylene diisocyanate, HDI), diphenylmethane 4,4'-, 2,4'-, or 2,2'-diisocyanate (MDI) and mixtures thereof. Relatively high-molar-mass compounds (b) used having hydrogen atoms reactive toward isocyanates are the well known compounds reactive toward isocyanates, for example polyesterols, polyetherols, and/or polycarbonatediols, which are usually subsumed under the term "polyols", with molar masses from 500 to 8000, preferably from 600 to 6000, in particular from 800 to less than 3000, and preferably with average functionality toward isocyanates of from 1 .8 to 2.3, preferably from 1 .9 to 2.2, in particular 2.

Examples are polyether polyols such as those based on well known starter substances and on conventional alkylene oxides, e.g. ethylene oxide, propylene oxide, and/or butylene oxide, preference being given to polyetherols based on propylene 1 ,2-oxide and ethylene oxide, and in particular polyoxytetramethylene glycols.

Polyesterols can be polyesters based on diacids and on diols. Diols preferably comprise diols having from 2 to 10 carbon atoms, e.g. ethanediol, butanediol, or hexanediol, in particular 1 ,4-butanediol, or a mixture thereof. Diacids can comprise any of the known diacids, for example linear or branched-chain diacids having from four to 12 carbon atoms, or a mixture thereof. Adipic acid is preferably used as diacid.

Chain extenders (c) used comprise well known aliphatic, araliphatic, aromatic, and/or cycloaliphatic compounds with molar mass of from 50 to 499, preferably difunctional compounds, such as diamines and/or alkanediols having from 2 to 10 carbon atoms in the alkylene radical, in particular 1 ,3-propanediol, 1 ,4-butanediol, 1 ,6-hexanediol, and/or di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and/or decaalkylene glycols having from 3 to 8 carbon atoms, and preferably corresponding oligo- and/or polypropylene glycols, and it is also possible here to use a mixture of the chain extenders. The ratio by weight of the relatively high-molar-mass compound (b) having hydrogen atoms reactive toward isocyanates to chain extender (c) can be from 0.5:1 to 20:1 , preferably from 1.5:1 to 13:1 , and a higher proportion of chain extender here gives a hard product. Suitable catalysts (d) which in particular accelerate the reaction between the NCO groups of the diisocyanates (a) and the hydroxy groups of the structural components (b) and (c) are the tertiary amines which are conventional and known from the prior art, e.g. triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiper- azine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane, and the like, and also in particular organometallic compounds, such as titanic esters, iron compounds, e.g. ferric acetylacetonate, tin compounds, e.g. stannous diacetate, stannous dioctoate, stannous dilaurate, or the dialkyltin salts of aliphatic carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate, or the like. The amounts usually used of the catalysts are from 0.0001 to 0.1 part by weight per 100 parts by weight of polyhydroxy compound (b).

Optional additives (e) correspond to those mentioned below and are in particular selected from blowing agents, surfactants, nucleating agents, lubricants and mold- release agents, dyes, pigments, antioxidants, e.g. with respect to hydrolysis, light, heat, or discoloration, metal deactivators, inorganic and/or organic fillers, reinforcing agents, and plasticizers. Polyethersulfones

Strictly speaking, polyethersulfone (PESU or PES) is poly(oxy-1 ,4-phenylsulfonyl-1 ,4- phenyl). However, in the terms of the present invention, polyethersulfones encompass polyarylenethersulfones in general, i.e. polymers containing arylene groups which are at least partly linked by ether groups and sulfonyl groups. Suitable arylene groups are for example phenylene, naphthylene, anthracenediyl and phenanthrenediyl; these may carry one or more substituents, e.g. halogen atoms, OH groups, alkyl groups, e.g. Ci-C4-alkyl groups, alkoxy groups, e.g. Ci-C4-alkoxy groups, sulfonic acid or sulfonate groups and the like. Apart from the mandatory O and SO2 linking groups, the arylene groups may be linked by single bonds (in which case the polyethersulfones could also be termed polyphenylsulfones), S, S=0, C=0, -N=N- and/or -CR^aR^b- linking groups, where R^a and R^b are independently of each other hydrogen, Ci-Ci2-alkyl, C1-C12- alkoxy- or C6-Cis-aryl (-CR^aR^b- being especially -CH2-, -C(CH3)2- (in which case the polyethersulfones could also be termed polysulfones) or -C(CF3)2-). Polysulfones

Strictly speaking, polysulfone (PSU) is obtained by polycondensation of bisphenol A and 4,4'-dichlorodiphenylsulfone. However, in the terms of the present invention, polysulfones encompass polyarylensulfones in general, i.e. polymers containing arylene groups which are at least partly linked by ether groups, sulfonyl groups and propan-2,2-diyl (-C(CH3)2-) groups. Suitable arylene groups are for example phenylene, naphthylene, anthracenediyl and phenanthrenediyl; these may carry one or more substituents, e.g. halogen atoms, OH groups, alkyl groups, e.g. Ci-C4-alkyl groups, alkoxy groups, e.g. Ci-C4-alkoxy groups, sulfonic acid or sulfonate groups and the like. Apart from the mandatory O, SO2 and propan-2,2-diyl (-C(CH3)2-) linking groups, the arylene groups may be linked by single bonds (in which case the polysulfones could also be termed polyphenylsulfones), S, S=0, C=0, -N=N- and/or -CR^aR^b- linking groups, where R^a and R^b are independently of each other hydrogen, Ci-Ci2-alkyl, fluorinated Ci-Ci2-alkyl, Ci-Ci2-alkoxy or C6-Cis-aryl (-CR^aR^b- being especially -CH2- or -C(CF₃)₂-).

Polyphenylsulfones

Strictly speaking, polyphenylsulfone (PPSU or PPSF) is obtained by polycondensation of biphenyl-4-4'-diol and 4,4'-dichlorodiphenylsulfone. However, in the terms of the present invention, polyphenylsulfones encompass in general polymers containing arylene and biarylene groups which are at least partly linked by ether groups and sulfonyl. Suitable arylene groups are for example phenylene, naphthylene,

anthracenediyl and phenanthrenediyl; these may carry one or more substituents, e.g. halogen atoms, OH groups, alkyl groups, e.g. Ci-C4-alkyl groups, alkoxy groups, e.g. Ci-C4-alkoxy groups, sulfonic acid or sulfonate groups and the like. Suitable biarylene groups are for example biphenylene and binaphthylene; these may carry one or more substituents, e.g. halogen atoms, OH groups, alkyl groups, e.g. Ci-C4-alkyl groups, alkoxy groups, e.g. Ci-C4-alkoxy groups, sulfonic acid or sulfonate groups and the like. Apart from the mandatory O, SO2 and single bond linking groups, the arylene groups may be linked by S, S=0, C=0, -N=N- and/or -CR^aR^b- linking groups, where R^a and R^b are independently of each other hydrogen, Ci-Ci2-alkyl, fluorinated Ci-Ci2-alkyl, C1-C12- alkoxy or C6-Cis-aryl (-CR^aR^b- being especially -CH2-, -C(CH3)2- (in which case the polyphenylsulfones could also be termed polysulfones) or -C(CF3)2-). lonomers

lonomers are polymers comprising repeat units of both electrically neutral repeating units and a fraction of ionized units (usually no more than 15 percent). Commercial examples include polystyrene sulfonate, Nafion® (sulfonated tetrafluoroethylene based fluoropolymer-copolymer; DuPont) and Hycar® (telechelic polybutadiene; Goodrich).

Thermoplastic elastomers (TPE) are a specific class of thermoplastic polymers. They are copolymers and can be generally described as materials which are processable as a melt at elevated temperature, are resistant to creep and exhibit elastomeric properties such as the ability to stretch to a moderate elongation and upon removal of the stress return to something close to its original shape. Typically, TPEs comprise hard crystalline or glassy domains and soft amorphous domains. Examples are ethylene-butene copolymers, ethylene-octene copolymers and also styrene-butadiene- styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-ethylene-butylene-styrene block copolymers (SEBS), and styrene-ethylene- propylene-styrene block copolymers (SEPS). Among these, preference is given to ethylene-butene copolymers and ethylene-octene copolymers.

The choice of polymers A and B and their combination is principally limited by only two conditions. First, the polymers must be chosen in such a way that they sufficiently adhere to each other so that stable core-shell particles are formed. Polymer adherence is generally based on electronic attraction, but mostly on van der Waals forces. In general, adherence is higher if the polymeric structure in A and B is chemically similar. Second, advantageously, polymer B is to be processable in liquid phase (see below description of the method for producing the core-shell particles of the invention). Thus it advantageously either has a low melting (or softening) point, suitably below 100°C or preferably below 80°C, or, preferably, it is soluble or swellable in a solvent with a boiling point of below 150°C, preferably below 130°C and more preferably below 1 10°C.

In a preferred embodiment, polymers A and B can be the same or different, but are both selected from the same polymer class. More preferably, they are both selected from polyamides or are both selected from polyurethanes or are both selected from polyolefins.

Additionally, polymer B is preferably selected so that it is soluble or swellable in a solvent with a boiling point of below 150°C, preferably below 130°C and more preferably below 1 10°C. As regards suitable solvents, reference is made to the remarks made to the method of the invention.

The molecular weight of polymers A and B is not critical and can vary in very wide ranges. For example, the number average molecular weight M_n can range from 500 to 25,000,000 or even higher or from 1000 to 15,000,000 or from 2000 to 10,000,000 or from 5000 to 5,000,000 g/mol. The weight average molecular weight M_w of polymers A and B can be in the range of from 500 to 30,000,000 or higher or from 1000 to

25,000,000 or from 2000 to 15,000,000 or from 5000 to 10,000,000 g/mol. If not specified otherwise, the molecular weights given are values as obtained with standard methods suitable for the respective polymer, such as gel permeation chromatography (GPC), rheological methods, e.g. viscosimetry; vapor pressure osmometry or light scattering.

Following specific examples of combinations of polymers A and B are given for illustration purpose; they are however not to impose any limitation to possible polymers or their combinations:

- Polymer A = PA 6; Polymer B = PA 6/66/136;

- Polymers A and B = polyether-polyurethane (e.g. prepared from polytetrahydrofuran with M = 1000, 1 ,4-butanediol as diol component and diphenylmethandiisocyanate

(MDI) as diisocyanate component)

- Polymer A and polymer B = polyester-polyurethane (e.g. prepared from a

polyesterdiol with M = 2000 which in turn is prepared from butanediol, hexanediol and adipic acid; 1 ,4-butanediol as diol component and M DI as diisocyanate component) - Polymer A = polypropylene; polymer B = ethylene/1 -octene copolymer.

In an alternative embodiment, polymer A or polymer B or both polymers A and B are a polymer blend. Preferably, only B is a blend. "Polymer blend" in this context relates to a mixture of two or more polymers differing in at least one of the monomers used for their preparation. The polymers in the polymer blend can belong to the same polymer class (for example all polymers of the blend can be polyamides, but differ in one or more of their polymerized monomers) or can belong to different polymer classes (for example one polymer is a polyamide and the other is a polyurethane). Like in case of the use of single polymers A and B, the choice of suitable polymers for preparing the blends is principally limited by the above two conditions, namely first that the polymers sufficiently adhere to each other so that stable core-shell particles are formed, and second that polymer (blend) B is processable in liquid phase. Suitable polymers and polymer blends can be readily determined by those skilled in the art, for example by simple preliminary experiments.

However, preferably, both polymers A and B are single polymers.

Apart from polymers A and B and the low bulk density carbon, the core-shell particles of the invention may contain further components, such as conventional additives.

Suitable conventional additives comprise for example surfactants, dispersants, antioxidants, UV absorbers/light stabilizers, metal deactivators, antistatic agents, reinforcing agents, fillers, nucleating agents, antifogging agents, biocides, plasticisers, lubricants, emulsifiers, colorants, pigments, rheology additives, mold release agents, tackifiers, catalysts, flow-control agents, optical brighteners, flameproofing agents, antidripping agents, and blowing agents.

Suitable surfactants are surface-active compounds, such as anionic, cationic, nonionic and amphoteric surfactants, block polymers, polyelectrolytes, and mixtures thereof. Such surfactants can be used as dispersant, solubilizer or wetter. Examples of surfactants are listed, for example, in McCutcheon's, Vol.1 : Emulsifiers & Detergents, McCutcheon's Directories, Glen Rock, USA, 2008 (International Ed. or North American Ed.).

Suitable anionic surfactants are for example alkali, alkaline earth or ammonium salts of sulfonates, sulfates, phosphates, carboxylates, and mixtures thereof. Examples of sulfonates are alkylarylsulfonates, diphenylsulfonates, alpha-olefin sulfonates, lignine sulfonates, sulfonates of fatty acids and oils, sulfonates of ethoxylated alkylphenols, sulfonates of alkoxylated arylphenols, sulfonates of condensed naphthalenes, sulfonates of dodecyl- and tridecylbenzenes, sulfonates of naphthalenes and alkyl- naphthalenes, sulfosuccinates or sulfosuccinamates. Examples of sulfates are sulfates of fatty acids and oils, of ethoxylated alkylphenols, of alcohols, of ethoxylated alcohols, or of fatty acid esters. Examples of phosphates are phosphate esters. Examples of carboxylates are alkyl carboxylates, and carboxylated alcohol or alkylphenol ethoxylates.

Suitable nonionic surfactants are for example alkoxylates, N-substituted fatty acid amides, amine oxides, esters, sugar-based surfactants, polymeric surfactants, and mixtures thereof. Examples of alkoxylates are compounds such as alcohols, alkylphenols, amines, amides, arylphenols, fatty acids or fatty acid esters which have been alkoxylated with 1 to 50 equivalents. Ethylene oxide and/or propylene oxide may be employed for the alkoxylation, preferably ethylene oxide. Examples of N-substituted fatty acid amides are fatty acid glucamides or fatty acid alkanolamides. Examples of esters are fatty acid esters, glycerol esters or monoglycerides. Examples of sugar- based surfactants are sorbitans, ethoxylated sorbitans, sucrose and glucose esters or alkylpolyglucosides. Examples of polymeric surfactants are home- or copolymers of vinylpyrrolidone, vinylalcohols, or vinylacetate. Suitable cationic surfactants are for example quaternary surfactants, for example quaternary ammonium compounds with one or two hydrophobic groups, or salts of long-chain primary amines. Suitable amphoteric surfactants are alkylbetains and imidazolines. Suitable block polymers are block polymers of the A-B or A-B-A type comprising blocks of polyethylene oxide and polypropylene oxide, or of the A-B-C type comprising alkanol, polyethylene oxide and polypropylene oxide. Suitable

polyelectrolytes are polyacids or polybases. Examples of polyacids are alkali salts of polyacrylic acid or polyacid comb polymers. Examples of polybases are

polyvinylamines or polyethyleneamines.

The antioxidants, light stabilizers, and metal deactivators that are optionally used advantageously have a high migration fastness and temperature resistance. Suitable antioxidants, UV absorbers/light stabilizers and metal deactivators are selected, for example, from groups a) to t). The compounds of groups a) to g) and i) represent UV absorbers/light stabilizers, whereas compounds of groups j) to t) work in particular as stabilizers: 4,4-diarylbutadienes (a), cinnamic esters (b),benzotriazoles (c),

hydroxybenzophenones (d), diphenylcyanoacrylates (e), oxalic diamides (f), 2-phenyl- 1 ,3,5-triazines (g), antioxidants (h), nickel compounds (i), sterically hindered amines (j), metal deactivators (k), phosphites and phosphonites (I), hydroxylamines (m), nitrones (n), amine oxides (o), benzofuranones and indolinones (p), thiosynergists (q), peroxide scavengers (r), polyamide stabilizers (s), and basic costabilizers (t).

Common antistatic agents are, for example, based on long-chain aliphatic amines (optionally ethoxylated) and amides, quaternary ammonium salts (e.g., behentrimonium chloride or cocamidopropyl betaine or the Catafor products from Rhodia), esters of phosphoric acid, polyethylene glycol esters or ethers, or polyols. Further examples are ionic liquids, such as the Basionic products from BASF, conductive polymers and conducting polymer nanofibers, particularly polyaniline nanofibers. Suitable fillers or reinforcing agents comprise, for example, pigments, such as carbon black, graphite, calcium carbonate, silicates, talc, mica, kaolin, bentonite, barium sulfate, metal oxides and metal hydroxides, wood flour and fine powders or fibers of other natural products, and synthetic fibers. Examples of suitable fibrous or pulverulent fillers further include carbon fibers or glass fibers in the form of glass fabrics, glass mats or filament glass rovings, chopped glass, glass beads, and wollastonite. Glass fibers can be incorporated both in the form of short glass fibers and in the form of continuous fibers (rovings).

Suitable pigments comprise, for example, carbon black, graphite, titanium dioxide, iron oxide and the like.

Carbon black and graphite in this context (i.e. as an additive filler or pigment) differ from the low bulk density carbon material used according to the present invention in having a higher bulk density. Suitable colorants comprise, for example, phthalocyanine dyes.

Suitable nucleating agents comprise, for example, inorganic materials, such as talc, metal oxides such as titanium oxide or magnesium oxide, phosphates, carbonates or sulfates of preferably alkaline earth metals; organic compounds such as

monocarboxylic or polycarboxylic acids and also their salts, such as 4-tert-butylbenzoic acid, adipic acid, diphenylacetic acid, sodium succinate or sodium benzoate; polymeric compounds, such as ionic copolymers ("ionomers"), for example.

Examples for lubricants are metal soap, such as calcium stearate, magnesium stearate or zinc stearate, butyl stearate, palmityl stearate, glycerol monostearate, ethylene bisstearyl amide, methylene bisstearyl amide, palmitic amide, stearic acid, behanic acid, polyethylene wax and the like.

Examples for flame retardants are halogen containing compounds such as

tetrabromobisphenol A, decabromodiphenyl oxide, decabromodiphenyl ethane, brominated carbonate oligomers, brominated epoxy oligomers, and

poly(bromostyrenes). Non-halogen flame retardants are various phosphorus based compounds, such as red phosphorous, ammonium polyphosphates, phosphoric esters, in particular triarylphosphates, such as triphenyl phosphate, tribenzyl phosphate, tricresyl phosphate, tri-(dimethylphenyl) phosphate, benzyl dimethylphosphate, di- (dimethylphenyl) phenyl phosphate, resorcinol-bis(diphenyl phosphate), recorcinol-bis- [di-(2,6-dimethylphenyl)-phosphate] (PX-200), aluminum diethylphosphinate (Exolit® OP 1230), but also aliphatic phosphates, such as tris(2-chloroisopropyl)phosphate (Lupragen® TCPP), aromatic polyphosphates, e.g. polyphosphates derived from bisphenols, such as the compounds described in US 2004/0249022), and phosphonic esters, such as dimethyl-methyl phosphonate and phosphonic acid (2-((hydroxyl- methyl)carbamyl)ethyl) dimethylester, and polycyclic phosphorous-containing compounds, such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO); melamine based materials such as melamine cyanurate, melamine borate or melamine pyrophosphate, and the hydroxides, oxides and oxide hydrates of group 2, 4, 12, 13, 14 and 15 (semi)metals, such as magnesium oxide or hydroxide, aluminium oxide, aluminum trihydrate, silica, tin oxide, antimony oxide (III and V) and oxide hydrate, titanium oxide and zinc oxide or oxide hydrate.

Suitable plasticizers comprise, for example, compounds which comprise at least one phenolic group, such as described, for example, in EP 1529814. It is moreover also possible to use polyesters whose molar mass is from about 500 to 1500 g/mol and which are based on dicarboxylic acids, on benzoic acids, and on at least one diol or triol, preferably on a diol. The diacid component used preferably comprises succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, and/or terephthalic acid, and the diol used preferably comprises 1 ,2-ethanediol, diethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, dipropylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol, and/or

1 ,6-hexanediol. The ratio here of dicarboxylic acid to benzoic acid is preferably 1 :10 to 10:1. EP 1556433 gives a more detailed description of these plasticizers, by way of example.

The choice of suitable additives depends in each case on the specific polymer A or B to be used as well as on the end use of the polymer composite to be produced with the core-shell granules of the invention and can be established by the skilled person. Further details concerning the abovementioned additives are available in the technical literature, e.g. Plastics Additive Handbook, 5th edition, H. Zweifel, editor, Hanser Publishers, Munich, 2001 .

The additives are used in typical amounts, for example in amounts of from 0.0001 % to 50% by weight, preferably 0.01 % to 20% by weight, in particular 0.01 to 10% by weight, based on the total weight of the polymeric material A or B.

The additives can either be already present in polymers A and/or B before the core- shell particles are prepared and/or they can be added during the preparation process of the core-shell particles.

The invention further relates to a method for preparing core-shell particles, where the core comprises a polymer A, and the shell comprises a polymer B and low bulk density carbon, where polymers A and B can be the same or different, comprising applying a liquid composition comprising polymer B and low bulk density carbon on solid particles of polymer A and solidifying the applied composition.

As regards suitable and preferred polymers A and B and low bulk density carbon, reference is made to the above remarks.

The liquid composition comprising polymer B and low bulk density carbon can either be a melt (generally a melt of polymer B containing low bulk density carbon in dispersed form) or a dispersion or solution comprising polymer B and low bulk density carbon. In term of the present invention, "dispersion" relates to any form of a mixture of a substance, which as a rule is either solid or liquid, generally solid, with a solvent (the more precise term is dispersant, but for the sake of simplicity, "solvent" is used).

Examples are suspensions, emulsions, solutions and also liquid gels. Analogously, "dispersed" relates to a substance which is dispersed in a solvent, i.e. suspended, emulsified or dissolved.

If the liquid composition is to be a melt, polymer B must be selected so that it has a rather low melting (or softening) point, such as below 100°C and preferably below 80°C.

In one embodiment, the liquid composition is a dispersion or solution containing polymer B and low bulk density carbon (and of course also a solvent). "Solution" in this context refers to a solution of polymer B, as low bulk density carbon is scarcely soluble in common solvents. Thus, the liquid composition is strictly speaking a suspension because of generally undissolved low bulk density carbon, but it is nevertheless termed "solution" if polymer B is present in dissolved form. The liquid composition is not mandatorily a solution of polymer B in a suitable solvent as long as it is finely dispersed therein. The polymer may for example also be present in swollen form, so that the liquid composition is rather gel-like. In any case, the liquid composition is suitably in a form to allow a uniform distribution of low bulk density carbon and polymer B on core polymer A.

Solvents for preparing a dispersion or solution of polymer B and low bulk density carbon are preferably selected from solvents which are solvents or swelling agents for polymer B. Suitable solvents naturally differ widely depending on polymer B used. Additionally, they have a boiling point of at most 150°C, preferably at most 130°C and in particular at most 1 10°C to allow easy removal for solidifying the applied solution or dispersion.

Examples are water, Ci-C4-alkanols, such as methanol, ethanol, n-propanol, isopropanol, butanol, isobutanol or tert-butanol, aliphatic ethers, such as diethylether, methyl-tert-butylether and methyl-isobutylether, cyclic ethers, such as tetrahydrofuran and dioxin, ketones, such as acetone and ethylmethyl ketone, alkanes, such as pentane and hexane, aromatic hydrocarbons, such as benzene and toluene, and mixtures thereof. The solution or dispersion preferably contains 0.01 to 50% by weight, more preferably 0.1 to 25% by weight, even more preferably 1 to 25% by weight, in particular 1 to 10% by weight of polymer B, based on the total weight of the solution or dispersion. The solution or dispersion preferably contains 0.01 to 20% by weight, more preferably 0.05 to 15% by weight, even more preferably 0.1 to 5% by weight, in particular 0.1 to 1 % by weight of low bulk density carbon, based on the total weight of the solution or dispersion. The liquid composition can moreover contain at least one conventional additive.

Suitable additives are listed above. Alternatively or additionally, the solid particles of polymer A can contain at least one conventional additive and/or polymer B can contain at least one conventional additive. However, if the core-shell particles of the invention are to contain at least one conventional additive, it is convenient to incorporate this via the liquid composition containing polymer B and low bulk density carbon.

The application of the liquid composition comprising polymer B and low bulk density carbon to solid particles of polymer A can be carried out by any suitable means known in the art for coating solid particles, e.g. by thoroughly mixing polymer particles A with a melt or solution or dispersion of polymer B and low bulk density carbon, e.g. via immersion, dousing or dipping; or by blowing or spraying the melt or solution or dispersion of polymer B and low bulk density carbon on the polymer particles A. For providing core-shell particles with a high concentration of graphene, blowing or especially spraying a melt or especially a solution or dispersion of polymer B and low bulk density carbon onto the polymer particles A is the most suitable method. Thus, in a specific embodiment, the solid particles of polymer A are spray-coated with the solution or dispersion containing polymer B and low bulk density carbon. Very specifically, this is carried out in a fluidized bed. Solidification of the applied liquid composition containing polymer B and low bulk density carbon can be carried out by cooling (if the liquid composition is a melt) or removing the solvent (if the liquid composition is a solution or dispersion), e.g. by filtration or evaporation of the solvent, e.g. by heating and/or applying reduced pressure.

The liquid composition is preferably a dispersion or solution containing polymer B and low bulk density carbon (and of course also a solvent). Thus, in a preferred

embodiment, the method of the invention comprises following steps:

(i) dissolving or dispersing a polymer B and low bulk density carbon in at least one solvent;

(ii) applying the solution or dispersion obtained in step (i) to solid particles of polymer A; and

(ii) removing the at least one solvent from the coated particles obtained in step (ii).

As regards the terms "solution" and "dispersion", suitable and preferred solvents, suitable and preferred amounts of polymer B and low bulk density carbon contained in the solution/dispersion, the application of the solution or dispersion to solid particles of polymer A and the removal of the solvent from the coated particles, reference is made to what has been said above.

The invention further refers to core-shell particles, obtainable by the method of the invention. Reference is made to what has been said above in context with core-shell particles and the method for producing them.

The core-shell particles of the invention are a means for a precise, unproblematic dosing/metering of low bulk density carbon in processes for producing polymer composites containing such low bulk density carbon. Accordingly, one advantage of the core-shell particles of the invention is that they can be used in continuous processes, such as extrusion, for producing polymer composites containing low bulk density carbon. Due to their well-defined content of low bulk density carbon, they allow the production of polymer composites which in turn have a well-defined content of well- distributed low bulk density carbon. Thus, the invention also relates to the use of the core-shell particles of the invention as a solid masterbatch for preparing polymers containing low bulk density carbon (= polymer composites containing low bulk density carbon).

In the plastics industry, concentrates of pigments and additives in a polymer matrix are characterized by the term masterbatch (MB). The pigments or additives are often present as granulates and in a concentration which is higher than in the final application form. They are added to the raw polymer for dyeing or for modifying the polymer's properties. Compared to pastes, powders or liquid additives, masterbatches enhance the process reliability and are very well processable.

In one aspect of the present invention, the core-shell particles serve as a solid masterbatch for preparing polymers containing low bulk density carbon, or in other words, for low bulk density carbon-containing polymer composites. The invention also relates to a method for preparing polymers containing low bulk density carbon, which method comprises preparing a melt comprising the core-shell particles of the invention and optionally also at least one polymer C, and further processing the melt, where polymers A, B and C can be the same or different. As already explained, this process can be a continuous one.

Polymer C is not a mandatory component as the polymer(s) of the core-shell particle itself/themselves can form the matrix for the further processed polymer. This is especially the case if the core is rather large as compared to the shell.

Suitable polymers C are preferably selected from the polymers listed above for polymers A and B. As the melt is generally stable if polymers A, B and C have similar electronic properties, it is preferred that polymer C is from the same class of polymers as at least one of polymers A and B, and, in particular, that it is even the same polymer as one of polymers A and B. More preferably, polymers A, B and C are all selected from polyamides or are all selected from polyurethanes or are all selected from polyolefins.

In the method for preparing polymers containing low bulk density carbon, the melt containing the core-shell particles and optionally at least one polymer C is preferably subjected to a melt-processing process. Suitable melt-processing processes are for example melt extrusion, optionally followed by a forming process, injection molding, reactive injection molding, compression molding, blow molding, rotomolding, film extrusion and the like.

The invention further relates to a polymer containing low bulk density carbon, obtainable by the method as described above. Such polymers are characterized by a predetermined, defined content of low bulk density carbon. If desired, the polymers can contain much higher amounts of low bulk density carbon than has been possible with the production methods of the art.

Finally, the invention relates to the use of the polymer of the invention as or for producing a gas barrier material, an electrically conductive material, a thermally conductive material or a mechanically reinforced material.

The gas barrier material is characterized by a significantly reduced permeability for all atmospheric gases, especially oxygen, nitrogen and carbon dioxide, further for water vapour as well as for hydrocarbon vapour, such as the vapour of alkanes, alcohols etc.. Especially, the gas barrier material is characterized by a significantly reduced permeability for nitrogen and water vapour.

The invention is now illustrated by the following figure and non-limiting examples.

Figure 1 is a photography of one of the core-shell granules obtained in example 1 .1 cut open in order to show that it has indeed a core-shell structure. The shell is dyed black by the incorporated graphene, while the core is pure white. Examples

Example 1 - Polyamides

1 .1 Preparation of core-shell particles with graphene as low bulk density carbon and (different) polyamides as polymers A and B

1600 ml of glass beads (SiLibeads, diameter: 1.25-1 .65 mm; from Sigmund Lindner GmbH, Germany) were placed into a 5 I stirring pot of a beadmill (Dispermat,

Getzmann, air pressure system). 100 g of polyamide granules (Ultramid® 1 C from BASF; PA 6/66/136) were added under stirring and dissolved in a mixture of 1512 g of ethanol and 378 g of water. After dissolution, 10.0 g of graphene (a commercial material characterized by a bulk density of 0.0067 cm³/g, a BET surface area of 481 m²/g, and containing 99.1 at% of C and 0.7 at% of O (C/O ratio = 141 .57) according to XPS) were added and the mixture was stirred for 4 h at 1700 rpm (ca. 300-400 W, 4.5 m/s). During this time, the interior temperature was kept at 20-25°C. The beads were removed to give 1830 g of a graphene dispersion (5% of polymer, 0.5% of graphene, based on the total weight of the dispersion).

700 g of polyamide granules (Ultramid® B36; PA 6; from BASF; length: ca. 3 mm, width: ca. 2.5-3 mm, mean weight per granule: 0.0129 g) were placed in a fluidized bed (diameter of the bottom: 100/150 mm, cylindrical height: ca. 300mm), fluidized with 100-170 Nm³/h nitrogen heated to 1 15°C and sprayed with the graphene dispersion during ca. 10 h (ca. 0.8 kg/h) (fluidized bed coating). 1 150 g of free-flowing, abrasion- resistant core-shell granules of a diameter of 3-4 mm were obtained.

For determining the graphene content in the core-shell granules, 200 coated granules were dried at 60°C for 24 h in a vacuum drying oven and weighed. The total weight was 3.6740 g. The weight of 200 non-coated granules was 2.5775 g. From the mass difference and the known composition of the shell (polyamide:graphene = 10:1 ) the graphene content was determined to be 2.71 % by weight, based on the total weight of the granules.

Figure 1 shows one of the obtained core-shell granules cut open in order to show that it has indeed a core-shell structure. The shell is dyed black by the incorporated graphene, while the core is pure white.

1 .2 Molding The core-shell granules obtained in step 1.1 were then used for polyamide melt processing. All components were dried in a vacuum oven at 80°C for 12 h. 17 g of the core shell granules obtained in step 1.1 were melted in a mini-injection molding machine (DSM) for 5 min. The molten granulate was then injection-molded. The injection-molding temperature was 275°C and the mold temperature 80°C. The molded samples were produced as small round plates with a dimension of 45 x 45 x 0.8 mm and used in example 1 .3.

1 .3 Properties - Volume resistivity Volume resistivity of the samples obtained in example 1 .2 was determined according to ISO 3915. The results are listed in the table below.

Example 2 - Polyurethanes

2.1 Preparation of core-shell particles with graphene as low bulk density carbon and thermoplastic polyurethane (TPU1 ) as polymers A and B

Getzmann, air pressure system). 100 g of a TPU (Elastollan 1 185 A10; BASF; a polyether-polyurethane prepared from polytetrahydrofuran with M = 1000,

1 ,4-butanediol and MDI; termed TPU 1 ) were added under stirring and dissolved in 1890 g of tetrahydrofuran. After dissolution, 10. Og of graphene (characteristics as in example 1 .1 ) were added and the mixture was stirred for 4 h at 1700 rpm (ca. 300- 400 W, 4.5 m/s). During this time, the interior temperature was kept at 20-25°C. The beads were removed to give 1618 g of a graphene dispersion (5% of polymer, 0.5% of graphene, based on the total weight of the dispersion).

800 g of TPU1 granules (Elastollan 1 185 A10; length: ca. 5 mm, width: ca. 2.5-3 mm, mean weight per granule: 0.033 g) were placed in a fluidized bed (diameter of the bottom: 100/150 mm, cylindrical height: ca. 300mm), fluidized with 150-170 Nm³/h nitrogen heated to 60°C and sprayed with the graphene dispersion during ca. 8.5 h (ca. 0.8 kg/h) (fluidized bed coating). 1 150 g of free-flowing, abrasion-resistant core-shell granules of a diameter of 4-6 mm were obtained.

For determining the graphene content in the core-shell granules, 320 coated granules were dried at 90°C for 2 h in a vacuum drying oven and weighed. The total weight was 15.243 g. The weight of 320 non-coated granules was 10.481 g. From the mass difference and the known composition of the shell (TPU:graphene = 10:1 ) the graphene content was determined to be 2.84% by weight, based on the total weight of the granules.

2.2 Molding The core-shell granules obtained in step 2.1 were processed to plates of 2 mm thickness in an injection molding machine (Engel ES 330/80 from Engel, Germany), from which specimens were stamped for test purposes and used in example 2.5.

For comparison, TPU 1 granules (Elastollan 1 185 A10; length: ca. 5 mm, width: ca. 2.5- 3 mm, mean weight per granule: 0.033 g) were subjected to the same injection molding process and used in example 2.5.

2.3 Preparation of core-shell particles with graphene as low bulk density carbon and thermoplastic polyurethane (TPU2) as polymers A and B

Getzmann, air pressure system). 100 g of a TPU (Elastollan C 85 A10; BASF; a polyester-polyurethane prepared from a polyesterdiol with M = 2000 which in turn is prepared from butanediol, hexanediol and adipic acid; 1 ,4-butanediol and MDI; termed TPU2) were added under stirring in 1890 g of tetrahydrofuran. Then, 10. Og of graphene (characteristics as in example 1 .1 ) were added and the mixture was stirred for 4 h at 1700 rpm (ca. 300-400 W, 4.5 m/s). During this time, the interior temperature was kept at 20-25°C. The beads were removed to give 1741 g of a graphene dispersion (5% of polymer, 0.5% of graphene, based on the total weight of the dispersion).

800 g of TPU2 granules (Elastollan C 85 A10; length: ca. 4 mm, width: ca. 2.5-3 mm, mean weight per granule: 0.033 g) were placed in a fluidized bed (diameter of the bottom: 100/150 mm, cylindrical height: ca. 300mm), fluidized with 150-170 Nm³/h nitrogen heated to 60°C and sprayed with the graphene dispersion during ca. 9 h (ca. 0.75 kg/h) (fluidized bed coating). 1 150 g of free-flowing, abrasion-resistant core-shell granules of a diameter of 4-5 mm were obtained.

For determining the graphene content in the core-shell granules, 320 coated granules were dried at 90°C for 2 h in a vacuum drying oven and weighed. The total weight was 15.784 g. The weight of 320 non-coated granules was 10.696 g. From the mass difference and the known composition of the shell (TPU:graphene = 10:1 ) the graphene content was determined to be 2.92% by weight, based on the total weight of the granules.

2.4 Molding The core-shell granules obtained in step 2.3 were processed to plates of 2 mm thickness in an injection molding machine (Engel ES 330/80 from Engel, Germany), from which specimens were stamped for test purposes and used in example 2.5.

For comparison, TPU2 granules (Elastollan C 85 A10; length: ca. 4 mm, width: ca. 2.5- 3 mm, mean weight per granule: 0.033 g) were subjected to the same injection molding process and used in example 2.5.

2.5 Properties - Volume resistivity and gas barrier properties Volume resistivity of the samples from examples 2.2 and 2.4 as well as of pure TPU 1 and TPU2 (controls) was determined according to ISO 3915. The specific nitrogen permeability was determined according to ISO 151051 and the water permeability according to ASTM F 1249.

Sample from Graphene Volume N2 permeability H2O permeability example content resistivity [cm³^m/(m²-day-bar] [g^m/(m²-day]

[Ω-cm]

TPU 1 0 8.3 x 10¹¹ 4.77 x 10⁴ 1 .72 x 10⁴

2.2 2.84% 3.0 x 10³ 2.67 x 10⁴ 9.47 x 10³ Sample from Graphene Volume N2 permeability H2O permeability example content resistivity [cm³^m/(m²-day-bar] [g^m/(m²-day]

[Ω-cm]

TPU2 0 1 .5 x 10¹¹ n.d. n.d.

2.4 2.92% 2.8 x 10³ 2.02 x 10⁴ 1 .04 x 10⁴ n.d. = not determined

Example 3 - Polyolefins 3.1 Preparation of core-shell particles with graphene as low bulk density carbon and (different) polyolefins as polymers A and B

158.8 g of a polyolefin elastomer (Engage® 8200 from Dow Chemical; an

ethylene/octene copolymer) were swollen in 3000 g of toluene under reflux. After cooling, 1990 g of the obtained gel were placed in a 5 I stirring pot of a beadmill

(Dispermat, Getzmann, air pressure system), and 1600 ml of glass beads (SiLibeads, diameter: 1.25-1.65 mm; from Sigmund Lindner GmbH, Germany) were added. Then 10. Og of graphene (characteristics as in example 1 .1 ) were added and the mixture was stirred for 4 h at 1700 rpm (ca. 300-400 W, 4.5 m/s). During this time, the interior temperature was kept at 20-25°C. The beads were removed to give 1764 g of a graphene dispersion (5% of polymer, 0.5% of graphene, based on the total weight of the dispersion).

800 g of polypropylene granules (Moplen® HP500N; from LyondellBasell; length: ca. 5 mm, width: ca. 2-3 mm, mean weight per granule: 0.033 g) were placed in a fluidized bed (diameter of the bottom: 100/150 mm, cylindrical height: ca. 300mm), fluidized with 150 Nm³/h nitrogen heated to 90°C and sprayed with the graphene dispersion during ca. 8 h (ca. 0.9 kg/h) (fluidized bed coating). 1210 g of free-flowing, abrasion-resistant core-shell granules of a diameter of 2-4 mm were obtained.

For determining the graphene content in the core-shell granules, 200 coated granules were dried at 60°C in a vacuum drying oven and weighed. The total weight was 8.738 g. The weight of 200 non-coated granules was 5.632 g. From the mass difference and the known composition of the shell (polyolefin:graphene = 10:1 ) the graphene content was determined to be 3.23% by weight, based on the total weight of the granules.

3.2 Molding The core-shell granules obtained in step 3.1 were then used for melt processing. All components were dried in a Helios adsorption dryer at 80°C for 1 h. The polymer components were stabilized with Irganox® B 215. 30 g of polypropylene (Moplen® HP500N) and 470 g of the core shell granules obtained in step 3.1 were melt-mixed in a single-screw extruder (Colin 30 mm Single Screw Extruder) at 200°C with a rotational speed of 80 rpm. The extrudate was compression-molded in a Colin P 300M Lab Press at 230°C to give a sheet from which test specimens of 50 x 60 x 2 mm were stamped and used in example 3.3.

Properties - Volume resistivity

Volume resistivity of the samples obtained in example 3.2 was determined according to ISO 3915. The results are listed in the table below.

Sample from example no. Graphene content Volume resistivity [Ω-cm]

3.2 3.0 % by weight 1 .5 x 10³

Claims

Core-shell particles, where the core comprises a polymer A; and the shell comprises a polymer B and low bulk density carbon having a bulk density of at most 0.2 g/cm³; where polymers A and B can be the same or different.

The core-shell particles as claimed in claim 1 , where the low bulk density carbon has a bulk density of at most 0.15 g/cm³, preferably of at most 0.1 g/cm³.

The core-shell particles as claimed in any of the preceding claims, where the shell comprises 0.1 to 99.9% by weight of low bulk density carbon, based on the total weight of polymer B and the low bulk density carbon.

The core-shell particles as claimed in claim 3, where the shell comprises 0.5 to 75, preferably 1 to 50% by weight of low bulk density carbon, based on the total weight of polymer B and the low bulk density carbon.

The core-shell particles as claimed in any of the preceding claims, where the particles comprise 0.01 to 25% by weight, preferably 0.1 to 15% by weight of low bulk density carbon, based on the total weight of the particles.

The core-shell particles as claimed in any of the preceding claims, where the low bulk density carbon is selected from graphene, carbon nanotubes, fullerenes, low bulk density carbon black, low bulk density graphite and mixtures thereof, and is preferably graphene.

The core-shell particles as claimed in any of the preceding claims, where polymers A and B are selected from thermoplastics and thermoplastic elastomers.

The core-shell particles as claimed in claim 7, where the thermoplastics are selected from polyolefins, vinylaromatic polymers, polyamides, polyesters, polyacetals, polycarbonates, thermoplastic polyurethanes (TPU),

polyethersulfones, polysulfones, polyphenylsulfones and ionomers.

The core-shell particles as claimed in claim 7, where the thermoplastic elastomers are selected from ethylene-butene copolymers, ethylene-octene copolymers, styrene-butadiene-styrene block copolymers (SBS), styrene- isoprene-styrene block copolymers (SIS), styrene-ethylene-butylene-styrene block copolymers (SEBS) and styrene-ethylene-propylene-styrene block copolymers (SEPS), and are preferably selected from ethylene-butene copolymers and ethylene-octene copolymers.

The core-shell particles as claimed in claim 8 or 9, where polymers A and B are both selected from polyamides or are both selected from polyurethanes or are both selected from polyolefins.

A method for preparing core-shell particles, where the core comprises a polymer A; and the shell comprises a polymer B and low bulk density carbon having a bulk density of at most 0.2 g/cm³; where polymers A and B can be the same or different; comprising applying a liquid composition comprising polymer B and low bulk density carbon on solid particles of polymer A and solidifying the applied composition.

The method as claimed in claim 1 1 , where the liquid composition is a melt or a dispersion or solution comprising polymer B and low bulk density carbon.

The method as claimed in any of claims 1 1 or 12, comprising following steps:

(iii) removing the at least one solvent from the coated particles obtained in step (ii).

14. The method as claimed in claim 13, where the at least one solvent is selected so as to be a solvent or a swelling agent for polymer B.

15. The method as claimed in any of claims 13 or 14, where the solution or

dispersion obtained in step (i) contains 0.01 to 50% by weight, preferably 1 to 25% by weight, of polymer B, based on the total weight of the solution or dispersion.

16. The method as claimed in any of claims 13 to 15 where the solution or dispersion obtained in step (i) contains 0.05 to 15% by weight, preferably 0.1 to 5% by weight, of low bulk density carbon, based on the total weight of the solution or dispersion.

17. The method as claimed in any of claims 13 to 16, where the application in step (ii) is carried out by spray-coating solid particles of polymer A with the solution or dispersion obtained in step (i).

18. The method as claimed in any of claims 1 1 to 17, where the low bulk density carbon has a bulk density of at most 0.15 g/cm³, preferably of at most 0.1 g/cm³.

19. The method as claimed in any of claims 1 1 to 18, where the low bulk density carbon is selected from graphene, carbon nanotubes, fullerenes, low bulk density carbon black, low bulk density graphite and mixtures thereof, and is preferably graphene.

20. The method as claimed in any of claims 1 1 to 19, where polymers A and B are selected from thermoplastics and thermoplastic elastomers.

21 . The method as claimed in any of claims 1 1 to 20, where polymers A and B are both selected from polyamides or are both selected from polyurethanes or are both selected from polyolefins.

22. Core-shell particles, obtainable by a method as defined in any of claims 1 1 to 21 .

23. The use of core-shell particles as defined in any of claims 1 to 10 or 22 as a solid masterbatch for preparing polymers containing low bulk density carbon.

24. A method for preparing polymers containing low bulk density carbon having a bulk density of at most 0.2 g/cm³, which method comprises preparing a melt comprising the core-shell particles as defined in any of claims 1 to 10 or 22 and optionally also at least one polymer C and further processing the melt; where polymers A, B and C can be the same or different.

The method as claimed in claim 24, comprising subjecting the core-shell particles as defined in any of claims 1 to 10 or 22 and optionally at least one polymer C to a melt-processing process. 26. Polymer containing low bulk density carbon having a bulk density of at most 0.2 g/cm³, obtainable by a method as claimed in any of claims 24 or 25. The use of a polymer as defined in claim 26 as or for producing a gas barrier material, an electrically conductive material, a thermally conductive material or a mechanically reinforced material.