CA2109024A1

CA2109024A1 - Flameproofed, mineral-filled thermoplastic moulding compounds with high tracking resistance

Info

Publication number: CA2109024A1
Application number: CA002109024A
Authority: CA
Inventors: Herbert Magerstedt; Klaus Zander; Dieter Freitag; Karsten-Josef Idel; Aziz E. Sayed
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1992-10-27
Filing date: 1993-10-22
Publication date: 1994-04-28
Also published as: EP0595123A1; JPH07300552A; EP0595123B1; ES2193139T3; DE59310335D1; DE4236122A1

Abstract

Flameproofed, mineral-filled thermoplastic moulding compounds with high trackingresistance Abstract Thermoplastic moulding compounds comprising A) 20 to 60 parts by weight of calcium magnesium carbonate hydrate, B) 30 to 80 parts by weight of polyalkylene terephthalate and C) 0 to 30 parts by weight of glass fibres, wherein the sum of A + B + C is 100 and wherein 1 to 20 parts by weight of polyalkylene terephthalate may optionally in each case be replaced by an aromatic polycarbonate and/or a rubber-elastic polymer with a glass transition temperature of <-10°C and wherein the moulding compound may contain 1 to 10 parts by weight of halogenated compounds and 0.5 to 5 parts by weight (based in each case on 100 parts by weight of A + B + C) of antimony trioxide or antimony pentoxide.

Description

2109~2~

Flamenroofed, mineral-filled thermopl lstic mouldin~ comPounds with hi~h trackin~ resist;lnce .~
The invention relates to the use of calcium magnesium carbonate hydrate in thermoplastic . moulding compounds based on polyalkylene terephthalate and optionally an aromatic polycarbonate and optionally a rubber-elastic polymer and optionally glass fibres and . mouldings produced from these thermoplastic moulding compounds7 in order to obtain high tracking resistance as well as high flane resistance, without damage to the.~ thermoplastic matrix.
:~.
As is known from the literature, for example from Kunststoffe 80 (1990~, p. 3 and 4, plastics such as thermosets, elastomers, polyamide, polycarbonate etc. may be flame-proofed by using minerals having a high content of water of crystallisation, such as for 10 exarnple magnesium hydroxide.

., It is clear from the above-mentioned references that, while plastic articles containing a mineral filler display high flame resistance, their properties are considerably impaired by `;! the high quantities (>45 wt.%) required ~or flame-proofing.

~urthermore EP-A 543,262, a reference which was not published prior to the priority date of the present application, discloses moulding compounds consisting of 30 to 80%
by weight of a thermoplastic polyester and 2û to 70% by weight of mixtures of metal carbonates of metals of subgroup 2 of the periodic system. The mixtures of metali, carbonates are preferably mixtures of calcium magnesium carbonate and magnesium carbonate.
. .

. 20 In contrast to the above reference the present application relates to optionally reinforced polyalkylene terephthalate moulding compounds which contain hydrated calcium magnesium carbonate in a "pure" form, and not in the form of a mixture, as well as to the use of caleilm1 magnesium carbonate hydrate in optionally reinforced polyalkylene :~ terephthalate moulding compounds, in order to improve the tracking resistance of .
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moulded articles produced therefroml and to a process ~or the production of suchmoulding compounds.

EP-A 57161 describes moulding compounds produced from thermoplastic moulding compounds containing dolomite. Due to the addition of dolomite the tracking resistance S can only be improved in the presence of flame-proofing agents.

By contrast, moulded articles produced from polyalkylene terephthalate moulding compounds containing calcium magnesium carbonate hydrate display high flame resistance and high tracking resistance, even withou~ the addition of flarne-proofing agents. The addition of flame-proofing agents also irnproves toughness.

lO Although the rheological properties of the products would have been expected to be greatly impaired as a result of the basic components, such effects are not observed.
Despite the basic cornponents the solution viscosity is equal to that of products not containing such components.

It has been found that high tracking resistance as well as high flame resistance and 15 advantageous other properties can be obtained with a polyalkylene terephthalate to which -, calcium magnesiurn carbonate hydrate has been added, without darnage to the ` therrnoplastic matrix.
ii The advantage of the use of the above additive in flameproofed systems is that it not only . has a flame-proofing effect but also produces high tracking resistance, while at the same 20 time being effectively incorporated in the therrnoplastic structure without any damage thereto and such low-cost systems are of great economic interest.

The object of the present invention is to provide a thermoplastic moulding compound based on polyalkylene terephthalate which contains a commercially available low-cost and correspondingly econornical filler, from which moulded articles or components can 25 be obtained which are distinguished by high flame resistance as well as high tracking resistance without clamage to the matrix.

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The present invention relates to thermoplastic moulding compouncls comprising ~; , ~, A) 20 to 60 parts by weight of calcium magnesium carbonate hydrate ` B) 30 to 80 parts by weight of polyalkylene terephthalate and`' C) 0 to 30 parts by weight of glass fibres, -S wherein the sum of A + B + C is 100, and wherein I to 20 parts by weight of . polyalkylene terephthalate may optionally in each case be replaced by an aromatic ~5~ polycarbonate and/or a rubber-elastic polymer with a glass transition temperature of < -;. 10C and wherein the moulding compound may contain 1 to 10 parts by weight of halogenated compounds and 0.5 to S parts by weight (based in each case on 100 parts 10 by weight of A + B + C) of antimony trioxide or antimony pentoxide.

. .
The moulding compounds according to the invention preferably have a low-voltage $racking of >400, and preferably >500 [grade].

The present invention also relates to the use of ,;
j . A) 20 to 60 parts by weight of calcium magnesium carbonate hydrate in `i, 15 B) 30 to 8Q parts by weight of polyalkylene terephthalate and ~1 C) 0 to 30 parts by weight of glass fibres, :
wherein the surn of A + B + C is 100, and wherein 1 $o 20 parts by weight of polyalkylene terephthalate may optionally in each case be replaced by an aromatic polycarbonate and/or a rubber-elas~lic polymer with a glass transition temperature of < -10C and wherein the moulding compound may contain 1 to 10 parts by weight of halogena$ed compounds and 0.5 to 5 parts by weight (based in each case on 100 parts ;- by weight of A + B + C) of antimony trioxide or antimony pentoxide, for the production of tracking-resistant moulded articles, and preferably moulded articles having a low-voltage tracking of >400, and preferably >500 [grade]. The moulded articles also have - 25 high flame resistance.
.

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Part of the polyalkylene terephthalate component may be replaced with arornatic polycarbonate and optionally rubber-elastic polymers with a glass transition temperatwre of < -10C. It is also possible according to the invention to add reprocessed constituents to the thermoplastic moulding compounds without negatively affecting the described 5 properties.

Component A:
The calcium magnesium carbonate hydrate used according to the invention is standard commercial natural mineral with or without surface treatment. Aminosilanes are generally used for surface treatment. Pinely divided (0.4-10 microns) Mg-Ca carbonate hydrate, 10 such as for example Securoc~ (Incemin AG), may be used (MgO = approx. 40%, CaO
= approx. 5.5%, ignition loss at 1100C = approx. 54~/o), c.f. examples.

Component B:
Polyalkylene terephthalates according to the invention are reaction products of aromatic dicarboxylic acids or their reactive derivatives (e.g. dimethyl esters or anhydrides) with 15 aliphatic, cycloaliphatic or araliphatic diols and mixtures of these reaction products.

Preferred polyalkylene terephthalates may be produced from terephthalic acid (or its reactive derivatives) and aliphatic or cycloaliphatic diols with 2 to 10 C atoms according to known methods (Kunststoff-Handbuch, vol. VIII, p. 695 et seq, Karl-Hanser Verlag, Munich 1973).
.
20 Preferred polyalkylene terephthalates contain, based on the dicarboxylic acid component at least 80, and preferably 90 mol%, of terephthalic acid radicals and at least 80, preferably at least 90 mol/O, based on the diol component, of ethylene glycol and/or 1,4-butanediol radicals.

The preferred polyalkylene terephthalates may contain, apart from terephthalic acid 25 radicals, up to 20 mol% of radicals of other aromatic dicarboxylic acids with 8 to 14 C
atoms, or aliphatic dicarboxylic acids with 4 to 12 C atoms, such as radicals of phthalic Le A 29 448-FC - 4 -~ 2~902~1 acid, isophthalic acicl, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, .; succinic acid, adipic acid, sebacic acid, azelaic acid, cyclohexanediacetic acid.
. . .
.` The preferred polyalkylene terephthalates may contain, apart from ethylene glycol or 1,4-.. butanediol radicals, up to 20 mol% of other aliphatic tiiols with 3 to 12 C atoms or 5 cycloaliphatic diols with 6 to 21 C atoms, f`or example radicals of 1,3-propanediol, 2-. ethyl-1,3-propanediol, neopentyl glycol, I,S-pentanediol, 1,6-hexanediol, 1,4-cyclo-.~ hexanedimethanol, 3-methyl-2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,2,4-trimethyl-`~ 1,3-pentanediol, and 1,6,2-ethyl-1,3-hexanediol, 2,2-diethyl-1,3- propanediol, 2,5-hexanediol, 1,4-di-(J3-hydroxyethoxy)benzene, 2,2-bis-(4-hydroxycyclohexyl)propane, 10 2,4-dihydroxy- 1,1,3,3-tetramethylcyclobutane~,2-bis-(3 -~-hydroxyethoxyphenyl)propane and 2,2-bis-(4-hydroxypropoxyphenyl)propane (DE-OS 24 07 674,24 07 776,27 15 932).
. . .
The polyalkylene terephthalates may be branched by incorporating relatively small quantities of tri- or tekahydric alcohols or tri- or tetrabasic carboxylic acids of the kind .. described, for example, in D~OS 19 00 270 and US patent 3 692 744. Examples of 15 preferred branching agents are trimesic acid, trimellitic acid, trimethylolethane, trimethylolpropane and pentaerythritol.

~ It is advisable to use no more than 1 mol% of branching agent related to the acid '. component.
. ~
1, Particularly preferred are those polyalkylene terephthalates produced solely from :~, 20 terephthalic acid and its reactive derîvatives (e.g. its dialkyl esters) and ethylene glycol d/or 1,4-butanediol (polyethylene terephthalate and polybutylene terephthalate~ and mixtures of these polyallylene terephthalates.
: .
, Preferred polyallylene terephthala~es are also copolyesters produced from at least two of the above-mentioned acid components and/or from at least two of the above-mentioned -, 25 alcohol components; poly-(ethylene glycol/1,4-butanediol) terephthalates are particularly ~ preferred copolyesters.
.1 .
. ~ I,e A 29 448-FC - 5 - ., - . ,.

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The polyalkylene terephthalates preferably used as component B generally have anintrinsic viscosity of approx. 0.4 to 1.5 dl/g, preferably 0.5 to 1.3 dl/g, measured in -phenol/o-dichlorobenzene (l:l parts by weight) at 25C.

Aromatic polycarbonates according to this invention are understood to be homopolycarbonates and mixtures of these polycarbonates, which are, for example, based on at least one of the following diphenols:

hydroquinone, resorcinol, dihydroxydiphenyls, bis-(hydroxyphenyl)alkanes, bis-(hydroxyphenyl~cycloalkanes, .- bis-(hydroxyphenyl) sulphides, bis-(hydroxyphenyl) ethers, bis-(hydroxyphenyl) ketones, ` 15 bis-(hydroxyphenyl) sulphones, , bis-(hydroxyphenyl) sulphoxides, a,oc'-bis-(hydroxyphenyl)diisopropylbenzenes and their r~ng-allylated and ring-halogenated derivatives.

., These and other suitable diphenols are, for sxample, described in US patents 3 028 365, 2 999 835, 3 148 172, 2 275 601, 2 991 283, 3 271 367, 3 062 781, 2 970 131 and 2 999 846, in D~OS 1 570 703, 2 063 050, 2 063 052, 2 211 956, 22 11 957, French patent --:~ 1 561 518 and in the monograph "H. Schnell, Chernistry and Physics of Polycarbonates, Interscience Publishers, New York 1964 Preferred diphenols are, for example:

.~
. 25 2,2-bis-(4-hydroxyphenyl)propane, ,, 1,1 -bis-(4-hydroxyphenyl)cyclohexane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)propane, , ~ Le A 29 448-FC - 6 -'.......... ~ ' , ' :_~. ' ~ ,, ' ' ' 210~24 .

2,2-bis-(3,5-dibromo-4-llydroxyphenyl)propane, 2,2-bis-(3 ,5-dimethyl-4-hydroxyphenyl)propane, bis-(3,5-dimethyl-4-hydroxyphenyl)methane, bis-(4-hydroxyphenyl) sulphide, . S 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, The diphenols may be used both individually and in the form of mixtures. Particularly preferred aromatic polycarbonates are polycarbonates based on 2,2-bis-(4-hydroxyphenyl) propane or one of the other diphenols listed as preferred. Very particularly preferred are those based on 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-(3,5-dimethyl-4-hydroxy-10 phenyl)propane or 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane or mixtures of 2,2-bis-(4-hydroxyphenyl)propane and 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclo-hexane.

The aromatic polycarbonates may be produced by known processes, e.g. by melt transesterification of an appropriate bisphenol with diphenyl carbonate and in solution 15 from bisphenols and phosgene. The solution may be homogeneous (pyridine process) or heterogeneous (two-phase interface process) (c.f. H. Schnell "Chemistry and Physics of Polycarbonates", Polymer Reviews, vol. IX, p. 33 et seq, Interscience Publ. 1964).

The aromatic polycarbonates as a mle have average molecular weights Mu~ of approx.
10,000 to 200,000, preferably 20,000 to 80,000 (determiIled by gel chromatography after 20 prior calibration).

Copolycarbonates according to the invention are in particular polydiorgano-siloxane/polycarbonate block copolymers with an average molecular weight M~, ofapprox. 10,000 to 200,000, preferably 20,000 to 80,000 (determined by gel chromatography after prior calibration) and a content of aromatic carbonate structural 25 units of about 75 to 97.S wt.%, preferably 85 to 97 wt.% and a content of ~ polydiorganosiloxane structural units of about 25 to 2.5 wt.%, preferably 15 to 3 wt.%, wherein the block copolymers are produced frorn polydiorganosiloxanes containing a,c~-.1 ~, Le A 29 448-FC - 7 -i I .. .. . .

.

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, bishydroxyaryloxy end groups, which poly~liorganosiloxat-es have a degree of polymerisation P,, of 5 to 100, preferably 20 to 80.
., ~-.......... The polydiorganosiloxane/polycarbonate block copolymers may also be a blenci of polydiorganosiloxane/polycarbonate block copolymers with customary thermoplastica 5 polycarbonates containing no polysiloxanes, wherein the total content of polydiorganosiloxane structural units in this blend is approx. 2.5 to 25 wt.%.
.
Such polydiorganosiloxane/polycarbonate block copolymers are characterised in that they - contain in the polymer chain, on the one hand, aromatic carbonate stmctural wnits (1) ~- and, on the other hand, polydiorganosiloxanes (2) containing aryloxy end groups, , O
ll (1), O--Ar~O--C--O--Ar-O--R 1 1 i (2) : R R1 R
.

.
in which ., ~ ,, ` Ar in each case denotes identical or different aryl radicals from diphenols and . . .
R and Rl are identical or different and denote linear alkyl, branched alkyl, alkenyl, halogenated linear alkyl, halogenated branched alkyl, aryl or halogenated aryl, but preferably methyl, ..
and :.
~, the number of diorganosiloxy units is n = a + b -~ c = 5 to 100, preferably 20 to 80.

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Alkyl in the above f`ormula (2) is, for example, Cl-C20 alkyl, alkenyl in the above formula (2) is, for example, C2-C6 alkenyl; aryl in the above formula (2) is C6-Cl4 aryl. -In the above formula, halogenated means partially or completely chlorinated, brominated `. or fluorinated.
.
5 Exarnples of alkyls, alkenyls, aryls, halogenated alkyls and halogenated aryls are methyl,ethyl, propyl, n-butyl, tert.-butyl, vinyl, phenyl, naphthyl, chloromethyl, perfluorobutyl, ' perfluorooctyl and chlorophenyl.

- Such polydiorganosiloxane/polycarbonate block copolymers are known, for example, from . US Patents 3 189 662, 3 821 325 and 3 832 419.

10 Preferred polydiorganosiloxane/polycarbonate block copolymers are produced by reacting polydiorganosiloxanes containing oc,a:)-bishydroxyaryloxy end groups together with other diphenols, optionally also using branching agents in customary quantities, for example : according to the two-phase interface process (see in this connection H. Schnell, ; Chemistry and Physics of Polycarbonates, Polymer Review, Vol. IX, p. 27 et seq, 15 Interscience Publishers, New York 1964), wherein in each case the ra$io of the bifunctional phenolic reactants is selected such that the content of aromatic carbonate . . structural units and diorganosiloxy units according to the invention is produced.

Such polydiorganosiloxanes containing a,~D-bishydroxyaryloxy end groups are known for exarnple from US 3 419 634.

$ 20 The rubber-elastic polymers comprise copolymers - in particular graft copolymers - with rubber-elastic properties, which are substantially obtainable from at least two of the following monomers:

chloroprene, isoprene, isobutene, styrene, acrylonitrile, ethylene, propylene, vinyl acetate and (rneth)acrylic acid est~rs with 1 to 18 C atoms in the alcohol component; namely ,~ 25 polymers of the kind described for example in "l\Iethoden der organischen Chernie"
(Houben-Weyl), vol. 14/1, Georg-Thieme Verlag, Stuttgart, 1961, pp. 393-406 and in Le A 29 448-FC - 9 -, , ~ .

902~
- C.B. Bucknall, "Toughened Plastics", Appl. Science Publishers, London, 1977. l he polymers have a gel content Or higher than 20, and preferably higher than 40 wt.%. The glass transition temperature (Tg) is below -20C.

Preferred polymers are selectively hydrogenated block copolymers of a vinyl aromatic S monomer (X) and a conjugated diene (Y) of the X-Y type. These block copolymers may be produced according to known processes.

In general, the technology used for the production of styrene/diene block polymers which is described in "Encyclopedia of Polymer Science and Technology", vol. 15, Interscience, NY (1971), pp. 508 et seq, may be used for the production of the suitable X-Y block ` 10 copolymers from styrene, a-methylstyrene, vinyl toluene etc. Selective hydrogenation may be performed by methods which are known per se and means that the ethylenic double bonds are substantially completely hydrogenated, while the aromatic double bonds rernain substantially unaffected.

Such selectively hydrogenated block copolymers are described, for example, in DE-OS
` 15 3 000 282.

Preferred polymers are, for example, polybutadienes grafted with styrene and/or acrylonitrile and/or (meth)acrylic acid alkyl esters, butadiene/styrene copolymers and poly(meth)acrylic acid esters, for example copolymers of styrene or alkylstyrene and conjugated dienes (high-impact polystyrene), i.e. copolymers of the type described in DE-OS 1 694 173 (= US patent 3 564 077), polybutadienes grafted with acrylic or methacrylic acid esters, vinyl acetate, acrylonitrile, styrene and/or alkylstyrenes, butadiene/styrene or butadiene/acrylonitrile copolymers, polyisobutenes or polyisoprenes of the kind described for exarnple in DE-OS 2 348 377 (= US patent 3 919 353) or in DE-A-3 105 364 and DE-A-3 019 233.

Particularly preferred polymers are, for example, ABS polymers (both blended andgrafted types) o:f the kind described, for example, in DE-OS 2 035 390 (= US patent 3 644 574) or in DE-OS 2 248 242 (= GB pa~ent 1 409 275).

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~! Particularly preferred polymers are furthermore those graft polymers obtainable by a ' grafting reaction of 1. 10 to 40, preferably 10 to 35 wt.%, based on the graft product, of at least one (meth)acrylic acid ester and/or a mixture of 1() to 40, and preferably 20 to 35 wt.%, based Ol1 the mixture, of acrylonitrile and 60 to 90, preferably 65 to 80 wt.%, based on the mixhlre, of styrene onto ., II. 60 to 90, preferably 65 to 90 wt.%, based on the graft product, of a butadiene polymer with at least 70 wt.%, based on II, of butadiene radicals as the grafting backbone, ::
.~ 10 wherein the gel content of the grafting backbone II is preferably > 70% (measured in toluene), the degree of grafting G is 0.15 to 0.55 and the average particle size d50 f the . graft polymer C is 0.2 to 0.6 llm, preferably 0.3 to 0.5 llrn (c.f. for exarnple EP 0 131 202).

(Meth)acrylic acid esters I are esters of acrylic acid or methacrylic acid and monohydric 15 alcohols with 1 to 8 C atoms.
,, x The grafting backbone II may contain, apart from butadiene radicals, up to 30 wt.%, ,~, based on II, of radicals of other ethylenically unsaturated monomers, such as for example :~ styrene, acrylonitrile, esters of acrylic or methacrylic acid with 1 to 4 C atoms in the .~ alcohol component (such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl !', 20 methacrylate). The preferred grafting backbone II consists of pure polybutadiene.

Since, as is known, in the grafting reaction, the graft monomers I are not completely . grafted onto the grafting backbone II, graft polymers according to the invention are also understood to be those products which, in addition to the actual graft polymers, also contain homo and copolymers of the grafting monomers I employed.
', , Le A 29 448-FC - 11 -, 21~902~
The degree of grafting G describes the weight ratio of grafted monomers to grafting backbone and is dimensionless.

The average particle size d50 is the diameter above and be]ow which lie the diameters of 50 wt.% of the particles. The diameter may be determined by ultracentrifuge 5 measurements (W. Scholtan, H. Lange, Kolloid Z., and Z. Polymere 250 (1972), pp. 782-796) or by means of electron microscopy and subsequent particle counting (C. Kampf, E~. Schuster, Angew. Makromolekulare Chemie 14, (1970), 111-129) or by light scattering measurements.

Particularly preferred rubber-elastic polymers are also, for example, graft polymers of a) 25 to 98 wt.%, based on 100 wt.% graft polymer, of an acrylate rubber with aglass transition temperature below -20C as the grafting backbone and b) 2 to 75 wt.%, based on 100 wt.% graft polymer, of at least one polymerisable,ethylenically unsaturated monomer, the homo or copolymers of which produced in the absence of (a) would have a glass transition temperature of 25C, as the graft monomers.

The acrylate rubbers (a) are preferably polymers of acrylic acid alkyl esters, optionally with up to 40 wt.% of other polymerisable ethylenically unsaturated monomers. If the acrylate rubbers used as the grafting backbone (a), as described below, are $hemselves already graft products with a diene rubber core, the diene mbber core is not included in 20 the calculation of this percentage. Prefe~red polymerisable acrylic acid esters include Cl-C8 alkyl esters, ~or exarnple methyl, ethyl, butyl, octyl and 2-ethylhexyl esters; halogen alkyl esters, preferably halogen Cl-C8 alkyl esters, such as chloroethyl acrylate and aromatic esters such as benzyl acrylate and phenethyl acrylate. They may be usedindividually or as mixtures.

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The acrylate rubbers (a) may be uncrosslinked or crosslinked, and preferably partially crosslinked.
, .. : Monomers with more than one polymerisable double boncl may be added for crosslinking.
. Preferred examples of crosslinking monomers are esters of unsaturated monocarboxylic acids with 3 to 8 C atoms or saturated polyols with 2 to 4 OH groups and 2 to 20 C
. atoms, such as for example ethylene glycol dimethacrylate, allyl methacrylate, polyunsaturated heterocyclic compounds, such as for example trivinyl and triallyl X~ cyanurate and isocyanurate, tris-acryloyl-s-triazine, in particular triallyl cyanurate;
,1 polyfunctional vinyl compounds such as di- and trivi:nyl benzenes; but also triallyl phosphate and diallyl phthalate.
'~:''1 x Preferred crosslinking monomers are allyl methacrylate, ethylene glycol dimethacrylate, diallyl phthalate and heterocyclic compounds having at least three ethylenicallyunsaturated groups.

Particularly preferred crosslinking monomers are the cyclic monomers triallyl i"yanurate, triallyl isocyanurate, trivinyl cyanurate, triacryloylhexahydro-s-triazine, triallyl benzenes.
rri The quantity of the crosslinking rnonomers is preferably 0.02 to S, in particular 0.05 to 2 wt.%, based on the grafting backbone (a).

.i In the case of cyclic crosslinking monomers with at least three ethylenically unsaturated 'j groups, it is advantageous to restrict the quantity to < I wt.% of the grafting backbone ~-~,, 20 (a) -"Other" preferred polymerisable ethylenically unsaturated monomers, apart from the acrylic acid esters, which may optionally be used to produce the grafting backbone (a) are, for example, acrylonitrile, styrene, a-methylstyrene, acryl~unides, vinyl Cl-C6 alkyl ,' ethers. Acrylate rubbers which are preferred as the grafting baclcbone (a) are emulsion : ~ 25 polymers with a gel content of 2 60 wt.%.

Le A 29 448-FC - 13 -, :', ..... ..
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:. The gel content of the grafting backbone (a) is determined in dimethylformamide at 25C
(M. Hoffmann, 11. Kramer, R. Kuhn, Polymeranalytik I & Il, Georg Thieme-Verlag, -Stuttgart 1977).
. .
Acrylate rubbers as the grafting backbone (a) may also be products containing a S crosslinked diene rubber made from one or more conjugated dienes, such as . polybutadiene, or a copolymer of a conjugated diene with an ethylenically unsaturated , monomer, such as styrene and/or acrylonitrile, as the core.

The proportion of the polydiene core in the grafting backbone (a) may be 0.1 to 80, preferably 10 to 50 wt.%, based on (a). The shell and core may, independemtly of one 10 another, be uncrosslinked, partially crosslinked or highly crosslinked.

Very particularly preferred are the previously mentioned graft polymers made from polybutadiene as the grafting base and (meth)acrylic acid esters and acrylonitrile as the grafted units, wherein the grafting backbone consists of 65 to 90 wt.% parts of crosslinked polybutadiene with a gel content of over 70% (in toluene) and the grafting 15 backbone of a S:1 to 20:1 mixture of methyl methacrylate and n-butyl acrylate (for `` example DE 3 105 364, DE 3 019 233).

The moulding compounds according to the invention can also contain I to 10, preferably ! 1 to S, parts by weight (based on 100 parts by weight of A + B + C) of halogenated compounds and 0.5 to 5, preferably 1 to 3 parts by weight (based on 100 parts by weight 20 of A + B + C) of antimony compounds, and in particular antimony trioxide or antimony pentoxide.
.
Exarnples of halogen-containing, and in particular brominated, organic cornpounds are:

ethylene- 1 ,2-bis-tetrabromophthalimide, epoxidised tetrabromobisphenol-A resin, 25 tetrabromobisphenol-A oligocarbonate and pentabromopolyacrylate.

Le A 29 448-FC - 14 --è~

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Epoxidised tetrabromobisphenol-A and tetrabromobisphenol-A oligocarbonate are preferably used.

Epoxidised tetrabromobisphenol-A is a known diepoxide resin with a molecular weight of about 350 to about 2,100, and preferably 360 to 1,000, and most preferably 370 to 5 400, and consists essentially of at least one condensatio:n product of bisphenol A and epihalohydrin and is defined by the forrnula (I) .

Cy, /CHCH=~ ~ C ~ OCH2CHCH20 ~ C ~ OCHz cy--~CH2 . n . ~
' wherein X represents hydrogen or bromine and n is an average number between zero and less than 2.3 (cf. for example :EP-A 180 .~ 471).
, Tetrabromobisphenol-A oligocarbonate is defined by the formula (II), the oligomers being - terrninated ei~er by phenol or by tribromophenol:
.

R~ C~O O-R ( ~

., :. Le A 29 448-FC - 15 -( .: . :. .

.:.~: : . ' : . ' ~ -` 2~0902 ..

R= ~O--,;~
~' or , . J
; Br ~; Br~O--; Br ;, .
,~. wherem :. .
. 5 X represents hydrogen or bromine and ~ n is an average number between 4 and 7.
.:
Tetrabromobisphenol-A oligocarbonate is known and can be produced by known ' methods.

; ~ The moulding compounds according to the invention, which contain the abovementioned flameproo~mg combination, have very high toughness.
., Component C
The glass fibres used are customary commercial glass fibres, which may also be surface treated.
., _ The m~ulding compounds may contain nucleating agents such as microtalc. The moulding 15 compounds may ~urthermore contain customary additives such as lubricants and mould , ., r~lease agents, processing stabilisers as well as dyes and pigments.
. ., 'l Moulded articles produced from the moulding cornpounds may be components for the electrical sector for which high tracking resistance as well as high flame resistance without damage to the thermoplastic matrix are required. Such articles may for example , 20 be casing parts, plug strips and light sockets as well as motor vehicle parts.

Le A 29 448-~C - 16 -,~

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'I'he moulding compounds according to the invention can be p'roduced by mixing the '. individual components in conventional mixing machines such as rollers, kneaders, or " single- or multi-screw extruders.

EXAl~'LES
', , 5 ,~ample 1 (according to the invention) 44.4 wt.% polybutylene terephthalate (PBT), intrinsic viscosity IV = 1.185 ~t ~, 0.015 ~-~ 45.0 wt.% calcium magnesium carbonate hydrate (Securoc~, Incemin AG) 10.0 wt.% glass fibres 100.6 wt.% additives . Examp!e 2 (according to the invention) 44.7 wt.% polybutylene terephthalate (PBT), intnnsic viscosity IV = 1.185 +
0.015 55.0 wt.% calcium magnesium carbonate hydrate (Securoc~, Incernin AG) ~: 15 0.3 wt.% additives Ex~,m,ple 3 (comparison) ' 64.9 wt.% polybutylene terephthalate (P~BT), intrinsic viscosity IV = 1.185 +
0.015 13.0 wt.% tetrabromobisphenol-A oligocarbonate (Great Lakes) 2012.0 wt.% glass fibres 4.5 wt.% antimony trioxide 0.6 wt.% additives Exa~mple 4 (comparison) 54.9 wt.% polybu~lene terephthalate (PBT), intrinsic viscosity IV = 1.185 + 0.015 10.0 wt.% tetrabromobisphenol-A oligocarbonate (Great Lakes) 30.0 wt.% glass fibres i LeA29448-FC - 17-. ..

'; ~
'',''=~ " ` , . `'`'` ;' '` ' 21~902~ :~
4.5 wt.% antimony trioxide 0.6 wt.% additives . .
Example S (according to the invention) 41.7 wt.% polybutylene terephthalate (PBT), intrinsic viscosity IV = 1.185 540.0 wt.% calcium magnesium carbonate hydrate (Securoc~ PBT/PP, Incemin AG) 3.0 wt.% tetrabromobisphenol-A oligocarbonate (Great Lakes) . 8.0 wt.% glass fibres . 1.5 wt.% antimony trioxide .~. 10 0.4 wt.% additives Example 6 (according to the invention) 52.1 wt.% polybutylene terephthalate (PBT), intrinsic viscosity IV = 1.185 ;~ 35.0 wt.% calcium magnesium carbonate hydrate - (Securoc~9 PBT~PP, Incernin AG) 15 3.0 wt.% tetrabromobisphenol-A oligocarbonate (Great Lakes) - . 8.0 wt.% glass fibres 1.5 wt.% antimony trioxide 0.4 wt.% additives The additives used are nucleating agents, processing stabilisers and mould release agents.
20 Comparison examples 3 and 4 additionally contain an antidripping agent.
. .
The components are compounded in an extruder and processed to form moulded parts in an injection moulding machine under customary processing conditions for polyallylene , . terephthalates (material temperature approx. 260C). Accordingly, the components j mentioned in the examples are also compounded in an extruder and moulded into test .' 25 specimens at a material temperature of approx. 260C.
.!
, ~, Le A 29 448-FC - 18 -, ii 210902~

s, Description of test methods:
. Low voltage tracking (CTI), test solution A accorcling to DIN standard VDE 0303, part -I, IEC 112.
, Flame testing according to UL 94/IEC 707 FV.
S Heat distortion temperature ~Vicat B) according to DIN 53 460.
Flexural test according to DIN 53 452.
;~ Relative viscosity (llre~) according to DIN 51 562, part 2 at 25C
Impact strength according to IZOD 180.
, The results are summarised in the ~ollowing table Le A 29 448-FC - 19 -,, . ;
, : . .... .
~ ~

~ . .

2109~24 `
, .
.
; Table ., . - ._ According Compariso n Accord-to the ing to invention the in-vention , .
Example Example Example Example Example Example .

Test solution A
S .. _ _ _ Flame test U L
0.8 mm V2 V0 V2 V2 V2 V2 1.6 mm V1 V0 V0 V0 V1 V1 _ 11 Heat dis-:. 10 tortion temperature Vicat B [C] 210 191 20S 210 210 210 . . _ Impact . stren~
15 I zod I
~kJ/m2] 19 10 20 ~ 41 22 28 :., _ I
Flexural test - Modulus of elasticity 20 [N/mm2] 10500 14750 5300 10100 8550 7 8C0 Rhe~
lkel 1.44 1.45 1.45 - _ I . _ __ . _ '.

( ~, Le A 29 448-~C - 20 -.~

Claims

1. Thermoplastic moulding compounds comprising A) 20 to 60 parts by weight of calcium magnesium carbonate hydrate, B) 30 to 80 parts by weight of polyalkylene terephthalate and C) 0 to 30 parts by weight of glass fibres, wherein the sum of A + B + C is 100 and wherein 1 to 20 parts by weight of polyalkylene terephthalate may optionally in each case be replaced by an aromatic polycarbonate and/or a rubber-elastic polymer with a glass transition temperature of < -10°C and wherein the moulding compound may contain 1 to 10 parts by weight of halogenated compounds and 0.5 to 5 parts by weight (based in each case on 100 parts by weight of A + B + C) of antimony trioxide or antimony pentoxide.

2. Moulding compounds according to Claim 1, wherein the low voltage tracking is >400 [grade].

3. Moulding compounds according to Claim 1, wherein the low-voltage tracking is >500 [grade].

4. Moulding compounds according to Claim 1, wherein ethylene-1,2-bistetrabromophthalimide, epoxidisedtetrabrornobisphenol-Aresins,tetrabromobisphenol-A oligocarbonate and/or pentabromopolyacrylate are used as the halogenated compounds.

5. The use of A) 20 to 60 parts by weight of calcium magnesium carbonate hydrate in B) 30 to 80 parts by weight of polyalkylene terephthalate and C) 0 to 30 parts by weight of glass fibres, wherein the sum of A + B + C is 100 and wherein 1 to 20 parts by weight of polyalkylene terephthalate may optionally in each case be replaced by an aromatic polycarbonate and/or a rubber-elastic polymer with a glass transition temperature of <-10°C and wherein the moulding compound may contain 1 to 10 parts by weight of halogenated compounds and 0.5 to 5 parts by weight (based in each case on 100 parts by weight of A + B + C) of antimony trioxide or antimony pentoxide, for the production of moulded articles having a low-voltage tracking of >400 [grade].