CA2315176A1 - X-ray opaque thermoplastic moulding compound - Google Patents

Abstract

Thermoplastic moulding compound containing (A) one or several vinyl polymers, (B) BaSO4 particles, and (C) optionally a bifunctional reactive compound polycondensate. The BaSO4 particles have an average diameter of more than 100 nm and a maximum average diameter of 3 000 nm. Also described is the use of the inventive moulding compound in the production of toys or medical items, in addition to moulded parts made from said moulding compound.

Description

Le A 32 716-foreign -I-A thermoplastic moulding composition which is opague to X-rays KM/Ke/NT
This invention relates to a thermoplastic moulding composition, and relates in particular to a thermoplastic moulding composition which is opaque to X-rays and which exhibits an outstanding notched bar impact strength.
The detection of plastics parts in the human body, e.g. of a swallowed plastics toy or of plastics particles which have accidentally become embedded in tissue, as well as the detection of articles of medical technology, is becoming increasingly important.
X-ray diagnostics is one method of detecting foreign bodies in the human organism.
Conventional plastics predominantly consist of elements of low atomic number (AN), such as carbon (AN = 6), hydrogen (AN = 1 ), oxygen (AN = 8) and nitrogen (AN
=
7). The effective atomic numbers of plastics are thus similar to that of water, so that I S the X-ray densities of conventional plastics and water are comparable.
Many conventional plastics are therefore substantially transparent in living tissue.
Elements of higher atomic numbers can be employed in plastics in order to increase the X-ray density thereof, e.g. chlorine (AN = 17) in polyvinyl chloride, silicon (AN =
14) in silicones and fluorine (AN = 9) in polyfluorocarbons. Of the conventional plastics, only polyvinyl chloride exhibits a contrast which is sufficient for X-ray diagnostics, due to its high chlorine concentration (Fortschr. Rontgenstr.
128, 6 (1978) 758 to 762).
Another possible way of increasing the X-ray density of plastics is to use fillers such as glass fibres (SiOz) or to employ colorants or pigments which consist of elements of higher atomic numbers, e.g. Ti02 (Ti: AN = 22).
Compounds which contain atoms with a high atomic number, such as BaS04 (Ba: AN
= 56), or organic iodine compounds (iodine: AN = 53), are used in medicine in order to make structures within the body visible by means of X-ray diagnostics.

Le A 32 716-foreign In order effectively to depict various plastics by means of X-rays, particularly those plastics which are without elements of a high atomic number (AN >8), BaS04 can be subsequently incorporated therein. The aforementioned organic iodine compounds are generally unsuitable for incorporation in plastics, since these compounds can decompose at the high temperatures used during the moulding of plastics.
If BaS04 is incorporated in a polymer, experience has shown that the X-ray contrast is significantly improved compared with the unfilled polymer. However, conventional fillers are incapable of significantly influencing the mechanical properties of the polymers obtained.
The underlying object of the present invention is therefore to provide thermoplastic moulding compositions which not only exhibit good X-ray contrast but which also possess outstanding mechanical properties.
This object is achieved by the provision of thermoplastic moulding compositions containing (A) one or more vinyl polymers, (B) BaS04 particles, and (C) optionally a polycondensate of bifunctional reactive compounds, which are characterised in that the BaS04 particles (B) have an average particle diameter of more than 100 nm and of 3000 nm at most.
The BaS04 particles preferably have an average particle size between 150 and nm, most preferably between 300 and 1000 nm.

Le A 32 716-foreign Surprisingly, the moulding compositions according to the invention exhibit a particularly favourable combination of properties, namely an outstanding notched bar impact strength and a high rigidity (modulus of elasticity).
Suitable vinyl polymers (A) comprise homopolymers or copolymers of one or more ethylenically unsaturated monomers which contain vinyl groups. Suitable monomers include vinyl acetate, styrene, a-methylstyrene, styrenes comprising substituted nuclei, acrylonitrile, methacrylonitrile, methyl methacrylate, malefic anhydride, N-substituted maleinimide, chloroprene, 1,3-butadiene, C,-C,8 alkyl acrylates and l0 methacrylates. The following are particularly suitable:
(A1) vinyl polymers which are free from rubber, (A2) vinyl polymers which contain rubber, e.g. graft polymers of vinyl monomers on a rubber, or (A3) mixtures of (Al) and (A2).
The graft polymers (A2) which are preferred according to the invention are those in which (a) styrene, or (b) methyl methacrylate, or (c) a mixture of (i) styrene, a-methylstyrene, styrenes comprising a substituted nucleus, methyl methacrylate or a mixture thereof, and (ii) acrylonitrile, methacrylonitrile, malefic anhydride, N-substituted maleinimides or a mixture thereof, are graft polymerised on to a rubber. In the case of (c), 95 to 50 % by weight of (i) and 5 to 50 % by weight of (ii) are preferably used. Suitable rubbers include all rubbers with glass transition temperatures <_10°C, preferably those which contain butadiene which is incorporated by polymerisation. Examples include polybutadiene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylate rubbers, optionally comprising incorporated structural units derived from butadiene, and acrylate rubbers which contain, as their nucleus, a crosslinked rubber such as polybutadiene or a copolymer of butadiene with an ethylenically unsaturated monomer such as styrene and/or ~0 acrylonitrile. Polybutadiene is preferred as the rubber.

Le A 32 716-foreign Graft (co)polymers (A2) preferably contain 10 to 95 % by weight, particularly 20 to 70 by weight, of rubber and 90 to 5 % by weight, particularly 80 to 30 % by weight, of graft (co)polymerised monomers. In these graft (co)polymers, the rubbers are present in the form of at least partially crosslinked particles with an average particle diameter (d5o) from 0.05 to 20 pm, preferably from 0.1 to 2 pm and most preferably from 0.1 to 0.8 um (as determined by ultracentrifugation, see W. Scholtan, H. Large, Kolloid, Z.
and Z. Polymer 250 (1972), pages 782 to 796).
Examples of vinyl polymers (A2) which contain rubber include graft copolymers with rubber-like elastic properties which can essentially be obtained from at least two of the following monomers: chloroprene, 1,3-butadiene, isoprene, styrene, acrylonitrile, ethylene, propylene, vinyl acetate, and C,-C,8 alkyl acrylates and methacrylates.
Polymers such as these are described, for example, in "Methoden der Organischen Chemie~(Houben-Weyl), Volume 14/1, Georg Thieme Verlag, Stuttgart, 1962, pages 393-406, and in C.B. Bucknall, "Toughened Plastics", Appl. Science Publishers, London 1977. The preferred polymers (A2) are partially crosslinked and have gel contents greater 20 % by weight, preferably greater than 40 % by weight, particularly greater than 60 % by weight.
The preferred rubber-like vinyl polymers (A2) are graft polymers comprising:
(A2.1 ) 5 to 95, preferably 30 to 80 parts by weight, of a mixture of (A2.1.1 ) 50 to 95 parts by weight styrene, a-methylstyrene, styrenes comprising halogen- or methyl-substituted nuclei, methyl methacrylate or mixtures of these compounds, and (A2.1.2) 5 to 50 parts by weight acrylonitrile, methacrylonitrile, methyl methacrylate, malefic anhydride, C,-C4 alkyl- or phenyl-N-substituted maleinimides, or mixtures of these monomers, on Le A 32 716-foreign (A2.2) 5 to 95, preferably 20 to 70 parts by weight of a rubber polymer with a glass transition temperature below -10°C.
Examples of preferred graft polymers (A2) include polybutadiene, butadiene/styrene copolymers and acrylic rubbers which are grafted with styrene and/or acrylonitrile and/or with alkyl acrylates or methacrylates; i.e. copolymers of the type described in DE-OS 16 94 173 (= US-PS 3 564 077); and butadiene, butadiene/styrene or butadiene/acrylonitrile copolymers, polyisobutenes or polyisoprenes which are grafted with alkyl esters of acrylic or methacrylic acid, vinyl acetate, acrylonitrile, styrene and/or alkylstyrenes, such as those described in DE-OS 23 48 377 (= US-PS 3 353).
Polymers (A2) which are particularly preferred are ABS polymers such as those described, for example, in DE-OS 20 35 390 (=US-PS 3 644 574) and in DE-OS 22 242 (= GB-PS 1 409 275).
Graft polymers (A2) which are particularly preferred can be obtained by the graft polymerisation of a) 10 to 70, preferably 15 to 50, particularly 20 to 40 % by weight with respect to graft polymer (A2), of acrylic acid esters or methacrylic acid esters, or of 10 to 70, preferably 15 to 50, particularly 20 to 40 % by weight of a mixture comprising 10 to 50, preferably 20 to 35 % by weight, with respect to the mixture, of acrylonitrile, acrylic acid esters or methacrylic acid esters and to 90, preferably 65 to 80 % by weight, with respect to the mixture, of styrene (as graft layer (A2.1 ), on b) 30 to 90, preferably 50 to 85, particularly 60 to 80 % by weight, with respect to graft polymer (A2), of a butadiene polymer comprising at least 50 % by weight, with respect to b), of butadiene radicals (as graft base (A.2.2), Le A 32 716-foreign wherein the gel content of graft base b) is preferably at least 40 % by weight (as measured in toluene), the degree of grafting G is 0.15 to 0.55 and the average particle diameter d5o of the graft polymer (A2) is 0.05 to 2 pm, preferably 0.1 to 0.6 pm.
The degree of grafting G is the ratio by weight of grafted-on graft monomers to the graft base (dimensionless number).
Acrylic acid esters or methacrylic acid esters a) are esters of acrylic acid or methacrylic acid and monohydric alcohols comprising 1 to 18 C atoms. Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl acrylate, t-butyl acrylate and t-butyl methacrylate are particularly preferred.
In addition to butadiene radicals, butadiene polymer b) can contain up to 50 %
by weight with respect to b) of radicals of other ethylenically unsaturated monomers, such as styrene, acrylonitrile, C,-C4 alkyl esters of acrylic or methacrylic acid (such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate), vinyl esters and/or vinyl ethers. Polybutadiene is preferred.
The preferred vinyl polymers (A 1 ) are copolymers which are formed from styrene, a-methylstyrene, styrenes comprising substituted nuclei or mixtures (A1.1), and from acrylonitrile, methacrylonitrile, methyl methacrylate, malefic anhydride, N-substituted maleinimide or mixtures thereof (A1.2). These copolymers preferably contain 50 to 98 % by weight of (A1.1) and 50 to 2 % by weight of (A1.2).
Copolymers (A 1 ) which are particularly preferred are those of (i) styrene, acrylonitrile and optionally methyl methacrylate, (ii) of a-methylstyrene, acrylonitrile and optionally methyl methacrylate, and (iii) those of styrene, oc-methylstyrene, acrylonitrile and optionally methyl methacrylate.

Le A 32 716-foreign _7_ The best known copolymers are styrene-acrylonitrile copolymers which can be produced by radical polymerisation, particularly by emulsion, suspension, solution or bulk polymerisation.
Copolymers (A1) preferably have molecular weights MW (weight average; as determined by light scattering or sedimentation) from 15,000 to 200,000.
Other particularly preferred copolymers (A 1 ) are randomly synthesised copolymers of styrene and malefic anhydride, which can be produced, for example, by the continuous bulk or solution polymerisation of the corresponding monomers with incomplete conversion. Their composition can be varied within wide limits. They preferably contain 5 to 25 % by weight of malefic anhydride units.
Instead of styrene, these polymers can also contain styrenes comprising substituted nuclei, such as p-methylstyrene, vinyltoluene or 2,4-dimethylstyrene, and other substituted styrenes such as a-methylstyrene.
Thermoplastic copolymers (A1) which are used according to the invention can be obtained from the monomers which are used for the production of graft copolymers (A2) and which are graft polymerised on to the rubber, or from similar monomers, and can be obtained in particular from styrene, a-methylstyrene, halogenated styrenes, acrylonitrile, methacrylonitrile, methyl methacrylate, malefic anhydride, vinyl acetate, N-substituted maleinimides or mixtures thereof. The preferred copolymers are those comprising 98 to 50 % by weight styrene, a-methylstyrene, methyl methacrylate or mixtures thereof with 2 to 50 % by weight acrylonitrile, methacrylonitrile, methyl methacrylate, malefic anhydride or mixtures thereof.
Copolymers (A1) such as these are also formed as by-products during the graft polymerisation of corresponding monomers, because graft polymerisation does not occur completely. In addition to the copolymers which are contained in graft polymer (A2), it is usual also to admix graft copolymers (A1) which are produced separately.

Le A 32 716-foreign _g_ The latter do not have to be chemically identical to the ungrafted resin fractions which are present in graft polymers (A2).
Thermoplastic copolymers (A l ) which are particularly preferred contain 20 to by weight acrylonitrile and 80 to 60 % by weight styrene or a-rnethylstyrene which are incorporated by polymerisation. These copolymers are known. They preferably have molecular weights from 15,000 to 200,000.
Any mixtures of polymers (A1) and (A2) can also be used as vinyl polymer (A).
Polycondensates (C), which are formed from bifunctional reactive compounds, are preferably polycarbonates and/or polyesters.
The preferred polycarbonates are those based on diphenols of formula (I) tB~x ~B)x OH
(I) ~ A ~ ~~ J
HO
wherein A represents a single bond, a C,-CS alkylene, a Cz-CS alkylidene, a CS-C6 cycloalkylidene, -O-, -SO-, -CO-, -S-, SOz-, or a C6-C,z arylene radical which is condensed with other aromatic rings which optionally contain hetero atoms, B is chlorine or bromine, x is0,lor2,and p is 1 or 0;

Le A 32 716-foreign and/or alkyl-substituted dihydroxydiphenylcycloalkanes of formula (II) H
(II) wherein R' and Rz, independently of each other, denote hydrogen, a halogen, preferably chlorine or bromine, a C,-C8 alkyl, a CS-C6 cycloalkyl, a C6-C,o aryl, preferably phenyl, and a C,-C,z aralkyl, preferably a phenyl-C,-C4-alkyl, particularly benzyl, m denotes an integer from 4 to 7, preferably 4 or 5, R3 and R4, independently of each other, denote hydrogen or a C,-C6 alkyl which can be selected individually for each Z, and Z denotes carbon, with the proviso that on at least one Z atom R3 and R4 simultaneously denote an alkyl, preferably methyl.
Polycarbonates which are suitable according to the invention include both homopolycarbonates and copolycarbonates.

Le A 32 716-foreign Polycondensate (C) can also be a mixture of the thermoplastic polycarbonates as defined above.
Polycarbonates can be produced in the known manner from diphenols and phosgene by the phase boundary method, or can be produced from diphenols and phosgene by the homogeneous phase method, which is termed the pyridine method, and their molecular weight can be adjusted in the known manner by a corresponding amount of known chain terminators.
Examples of suitable chain terminators include phenol, p-chlorophenol, p-tert.-butyl phenol or 2,4,6-tribromophenol, and also include long-chain alkylphenols, such as 4-(1,3-tetramethyl-butyl)phenol according to DE-OS 2 842 005, or monoalkylphenols or dialkylphenols with a total of 8 to 20 carbon atoms in their alkyl substituents according to DE-A-35 06 472.2, such as 3,5-di-tert.-butylphenol, p-iso-octylphenol, p-tert.-octylphenol, p-dodecylphenol, 2-(3,5-)phenol and 4-(3,5-dimethylheptyl)-phenol.
The amount of chain terminators generally ranges between 0.5 and 10 mol % with respect to the molar weight of diphenols (I) which are used in each case.
Polycarbonates (C) which are used according to the invention have average molecular weights (MW, weight average, as measured, for example, by ultracentrifugation or light scattering) from 10,000 to 200,000, preferably from 20, 000 to 80,000.
Example of suitable diphenols of formula (I) include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, 2,2-bis-(4-hydroxyphenyl)propane, 2,4-bis-(4-hydroxyphenyl)-methylbutane, 1,1-bis-(4-hydroxyphenyl)cyclohexane, 2,2-bis-(3-chloro-4-hydroxy-phenyl)propane and 2,2-bis(3 ,5 -dibromo-4-hydroxyphenyl)propane.
The preferred diphenols of formula (I) are 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-s0 (3,5-dichloro-4-hydroxyphenyl)propane and l,l-bis-(4-hydroxyphenyl)-cyclohexane.

Le A 32 716-foreign The preferred diphenols of formula (II) are l,l-bis-(4-hydroxyphenyl)-3,3-dimethyl-cyclohexane, 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 1,1-bis-(4-hydroxyphenyl)-2,4,4-trimethyl-cyclopentane.
Polycarbonates (C) which are used according to the invention can be branched in the known manner, preferably by the incorporation of 0.05 to 2.0 mol %, with respect to the sum of the diphenols used, of tri-functional compounds or of compounds with a functionality greater than three, e.g. those comprising three or more than three phenolic groups.
Apart from bisphenol A homopolycarbonate, the preferred polycarbonates include copolycarbonates of bisphenol A with up to 15 mol %, with respect to the molar sum of diphenols, of 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)propane.
Aromatic polyesters can also be used as the polycondensate (C).
The preferred polyesters (C) are polyalkylene terephthalates. These are the reaction products of aromatic dicarboxylic acids (or of reactive derivatives thereof, e.g.
dimethyl esters or anhydrides) and aliphatic, cycloaliphatic or arylaliphatic diols and mixtures of reaction products such as these.
The preferred polyalkylene terephthalates can be produced by known methods from terephthalic acid (or reactive derivatives thereof) and aliphatic or cycloaliphatic diols comprising 2 to 10 carbon atoms (Kunststoff Handbuch, Volume VIII, page 695 et seq., Carl Hanser Verlag, Munich 1973).
The preferred polyalkylene terephthalates contain 80 to 100, preferably 90 to 100 mol %, with respect to the dicarboxylic acid component, of terephthalic acid radicals, and 80 to 100, preferably 90 to 100 mol %, with respect to the diol component, of ethylene s0 glycol and/or 1,4-butanediol. In addition to terephthalic acid radicals, 0 to 20 mol of radicals of other aromatic dicarboxylic acids comprising 8 to 14 C atoms or of Le A 32 716-foreign aliphatic dicarboxylic acids comprising 4 to 12 C atoms are contained, such as radicals of phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, succinic, adipic, sebacic, azelaic or cyclohexanediacetic acid. Apart from ethylene glycol and/or 1,4-butanediol radical, 0 to 20 mol %
of other aliphatic diols comprising 3 to 12 C atoms or of cycloaliphatic diols comprising 6 to 12 C atoms are contained, e.g. radicals of 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 3-methylpentanediol-1,3 and -1,6, 2-ethylhexanediol-1,3, 2,2-diethylpropanediol-1,3, hexanediol-2,5, 1,4-di-(3-hydroxyethoxyphenyl)propane, 2,4-dihydroxy-1,1,3,3-tetrarnethylcyclobutane, 2,2-bis-(3-~3-hydroxyethoxyphenyl) propane and 2,2-bis-(4-hydroxypropoxyphenyl)propane (DE-OS 2 407 647, 2 407 776, 2 715 932).
The polyalkylene terephthalates can be branched by the incorporation of relatively small amounts of tri- or tetrahydric alcohols or of tri- or tetrabasic carboxylic acids, such as those which are described in DE-OS 1 900 270 and US-PS 3 692 744.
Examples of preferred branching agents include trimesic acid, trimellitic acid, trimethylolethane and -propane and pentaerythritol. It is advisable to use no more than 1 mol % of the branching agent with respect to the acid component.
Polyalkylene terephthalates which are particularly preferred are those which have been produced solely from terephthalic acid (or from reactive derivatives thereof, e.g.
dialkyl esters thereof) and ethanediol and/or 1,4-butanediol, as well as mixtures thereof.
The preferred polyalkylene terephthalates also include copolyesters which are produced from at least two of the aforementioned diols; the most preferred copolyesters are poly-(ethylene glycol/1,4-butanediol) terephthalates. The various diol radicals can be present in the copolyesters in the form of blocks or in randomly distributed form.

Le A 32 716-foreign The polyalkylene terephthalates generally have an intrinsic viscosity of 0.4 to 1.4 dl/g, preferably 0.5 to 1.3 dl/g, particularly 0.6 to 1.2 dl/g, as measured in each case in phenol/o-dichlorobenzene (1:1 parts by weight) at 25°C.
The BaS04 particles (B) which are used according to the invention have an average particle diameter d5° which is greater than 100 nm but which is 3000 nm at most. The average particle diameter ds° is defined as the diameter above and below which 50 by weight of the particles are present. It can be determined by means of ultracentrifuge measurements (W. Scholtan, H. Lange, Kolloid. Z. and Z.
Polymere 250 (1972), 782-796).
For example, the following commercially available products can be used:
Sachtoperse HP, Blanc fixe N, XR-HX (manufactured by Sachtleben Chemie GmbH, Duisburg);
Blanc fixe HD 80 (Solway Barium Strontium GmbH, Hanover).
The BaS04 particles (B) preferably have an average particle diameter between 200 and 2000 nm, most preferably between 300 and 1000 nm.
Moreover, the barium sulphate can also be present in the form of a master batch and can be incorporated in the thermoplastic moulding composition.
The master batch is present in a solid form (e.g. as granules or powder), or in a paste-like or liquid form. High molecular weight substances (polymers) or low molecular weight substances (e.g. waxes, oils) are generally employed as supports. The vinyl polymers which were described above as component A) are preferably used as the supporting substance. Customary additives, such as pigments, waxes and oils, can be added to the master batch.
The master batch generally contains 1-80 % by weight, preferably 5 to 60 % by ,0 weight, of barium sulphate with respect to the total master batch.

Le A 32 716-foreign Processes for producing a master batch are described, for example, in "Pigment and Additive Concentrates" by Heini Griitter, in "Mixing of Plastics", VDI-Verlag GmbH
1983, Dusseldorf.
In the single-stage process, the support, barium sulphate and optionally additives are mixed in the customary manner and are subsequently compounded.
In the double-stage process, the supporting polymer is first melted, and the barium sulphate and optionally additives are then introduced and dispersed in this melt in the customary manner.
In addition to the components according to the invention, the moulding compositions can contain customary additives, such as pigments, fillers, stabilisers, anti-static agents, internal lubricants, demoulding agents and flame retardants, provided that these do not reduce the notched bar impact strength.
The BaS04 particles (B) or the master batch can be incorporated into the thermoplastic moulding composition (A) and optionally into polycondensate (C) by customary methods, for example by the direct kneading or extrusion of plastics (A) and optionally of (C) and of the BaS04 particles (B), and optionally of the other adjuvant substances also. The amount of BaS04 which is added, optionally as a mixture with polycondensate (C), to polymer (A), is preferably 0.1 to 50, more preferably 0.1 to 30 and most preferably 0.1 to 10 % by weight BaS04. Mixing is effected at elevated temperatures, e.g. at 100°C to 280°C, in customary mixer units, kneaders, internal mixers, cylinder mills, continuous screw machines or extruders.
Depending on the intensity of mixing, the dwell times during the mixing process can vary between 10 seconds and 30 minutes.
The moulding compositions which are thus obtained are then further processed in a customary manner, e.g. by injection moulding, to form mouldings, particularly toys or articles of medical technology such as catheters for example.

Le A 32 716-foreign - IS -The following examples explain the invention in greater detail.
Examples Thermoplastic moulding compositions were produced by kneading the constituents ABS, SAN, and BaS04, as well as with various customary additives (pigments, demoulding agents, anti-static agents and internal lubricants) in a Farelle plunger kneader at 170-185 °C, at a speed of rotation of 590 miri' and for a kneading duration of 3-5 minutes. The moulding compositions which were thus produced were rolled (roll temperature 1 SO°C) and granulated, and were injection moulded to form test specimens in an injection moulding machine manufactured by Arburg, using a 75 t locking pressure at 240°C material temperature, 70°C mould temperature and an injection moulding speed of 40 mm/sec.
The test specimens produced in this manner were tested according to the following standards:
1. Melt index (Volume Flow Index MVR) ISO 1133 2. Izod notched bar impact strength ISO 180/lA flat bar, 80x10x4 mm3 3. Tensile modulus of elasticity ISO 527 shouldered bar No. 3; 170x10x4 mm' The results of the tests are presented in the Table below.
The polymer composition of the polymers listed in the Table was identical in each case, and was as follows:
SAN is a thermoplastic resin comprising 28 % by weight acrylonitrile and 72 %
by weight styrene. SAN can be produced by emulsion polymerisation (SAN latex) or by bulk polymerisation methods. The viscosity of the SAN resin is characterised by its L

Le A 32 716-foreign value (L value = rlsp~~/c, where c = 5 g/1 in DMF at 25°C). The L value of the SAN
used was 60.
ABS graft polymer in the form of a powder is produced by the emulsion polymerisation of styrene and acrylonitrile in the presence of an aqueous polybutadiene emulsion (polybutadiene graft base). Styrene and acrylonitrile are grafted on to the polybutadiene. As is known, grafting does not occur completely, so that free SAN is also present in the ABS graft powder in addition to grafted SAN. The ABS graft polymer consisted of 55 % by weight polybutadiene and 45 % by weight SAN (styrene:acrylonitrile = 72 % by weight : 28 % by weight). The particle size of the polybutadiene graft base was 0.4 ~.m.
T.~hlo Example A B C D E F
(comp-(comp- (comp-arative)arative) arative) BS graft polymer parts 35 35 35 35 35 35 by weight SAN resin parts 65 65 65 65 65 65 by weight coloured pigments parts 9 9 9 9 9 9 dditives demouldingby weight agents internal lubricants BaS04 (100 nm) parts 9.5 by weight aS04 (700 nm) parts 9.5 by weight aS04 ( I 000 nm) parts 9.5 by weight BaS04 (30 nm) parts 9.5 by weight BaS04 (200 nm) parts 9.5 by weight esults:

filling pressure bar 142.1 140.6l44 147.5 142.5139 K Izod 240C/23C kJ/m~ 23.7 12.3 20.1 18.9 10.4 13.9 K Izod 240C/0C kJ/m~ 19.2 9.1 14.6 13.7 7.4 10.2 K Izod 240C/-10C kJ/m~ 17.9 7.9 13 11.6 8.3 8.9 aK Izod 240C/-20C k.l/m~ 16 5.8 8.9 8.5 5.5 6.8 MVR ccm/l0 32.1 28.4 30.3 29.2 26 29.9 min.

ensile modulus of N/mm~ 2155 2253 2241 2244 2238 2275 elasticity ~S

Claims (14)

Claims

1 A thermoplastic moulding composition containing (A) one or more vinyl polymers, (B) BaSO4 particles, and (C) optionally a polycondensate of bifunctional reactive compounds, characterised in that the BaSO4 particles have an average particle diameter of more than 100 nm and of 3000 nm at most.

2. A moulding composition according to claim 1, characterised in that the BaSO4 particles have an average particle diameter between 200 and 2000 nm.

3. A moulding composition according to claims 1 or 2, characterised in that vinyl polymer (A) is selected from (A1) vinyl polymers which are free from rubber, (A2) vinyl polymers which contain rubber, (A3) mixtures of (A1) and (A2).

4. A moulding composition according to any one of claims 1 to 3, characterised in that vinyl polymers (A1) which are free from rubber are selected from copolymers of (A1.1) styrene, .alpha.-methylstyrene, styrenes comprising substituted nuclei or mixtures thereof, and (A1.2) acrylonitrile, methacrylonitrile, methyl methacrylate, malefic anhydride, N-substituted maleinimide or mixtures thereof.

5. A moulding composition according to claim 4, characterised in that copolymer (A1) contains 50 to 98 % by weight (A1.1) and 50 to 2 % by weight (A1.2).

6. A moulding composition according to any one of claims 1 to 5, characterised in that copolymer (A1) is a copolymer of (i) styrene, acrylonitrile and optionally methyl methacrylate, (ii) .alpha.-methylstyrene, acrylonitrile and optionally methyl methacrylate, or (iii) styrene, .alpha.-methylstyrene, acrylonitrile and optionally methyl methacrylate.

7. A moulding composition according to one or more of claims 1 to 6, characterised in that vinyl polymers (A2) which contain rubber are graft polymers comprising (A2.1) 5 to 95, preferably 30 to 80 parts by weight, of a mixture of (A2.1.1) 50 to 95 parts by weight styrene, .alpha.-methylstyrene, styrenes comprising halogen- or methyl-substituted nuclei, methyl methacrylate or mixtures of these compounds, and (A2. 1.2) 5 to 50 parts by weight acrylonitrile, methacrylonitrile, methyl methacrylate, malefic anhydride, C1-C4 alkyl- or phenyl-N-substituted maleinimides, or mixtures of these compounds, on (A2.2) 5 to 95, preferably 20 to 70 parts by weight of a rubber polymer with a glass transition temperature below -10°C.

8. A moulding composition according to any one of claims 1 to 7, characterised in that graft polymer (A2) is obtained by the graft polymerisation of a) 10 to 70 % by weight, with respect to graft polymer (A2), of acrylic acid esters or methacrylic acid esters, or of 10 to 70, preferably 15 to 50, particularly 20 to 40 % by weight of a mixture of 10 to 50, preferably 20 to 35 % by weight, with respect to the mixture, of acrylonitrile, acrylic acid esters or methacrylic acid esters, and 50 to 90, preferably 65 to 80 % by weight, with respect to the mixture, of styrene (as graft layer (A2.1)) on b) 30 to 90, preferably 50 to 85, particularly 60 to 80 % by weight, with respect to graft polymer (A2), of a butadiene polymer comprising at least 50 % by weight, with respect to b), of butadiene radicals (as graft base (A2.2)).

9. A moulding composition according to any one of claims 1 to 7, characterised in that polycondensate (C) is a polycarbonate or polyester.

10. A moulding composition according to any one of the preceding claims, characterised in that the barium sulphate is present in the form of a master batch.

11. The use of a moulding composition according to any one of claims 1 to 10 for the production of mouldings.

12. A use according to claim 11 for the production of toys or articles of medical technology.

13. Mouldings produced according to any one of claims 1 to 10.

14. Toys and articles of medical technology according to claim 13.