CA2019904A1

CA2019904A1 - Flameproofed thermoplastic molding materials

Info

Publication number: CA2019904A1
Application number: CA002019904A
Authority: CA
Inventors: Petra Baierweck; Gerd Blinne; Manfred Koetting
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1989-07-27
Filing date: 1990-06-27
Publication date: 1991-01-27
Also published as: JPH0366755A; EP0410301B1; EP0410301A1; DE3924869A1; JP3068164B2; ES2060874T5; EP0410301B2; DE59007375D1; ES2060874T3

Abstract

O.Z. 0050/40971 Abstract of the Disclosure: Flameproofed, thermoplastic molding materials contain, as essential components, A) 10-98% by weight of a partly aromatic copolyamide, essentially composed of a1) from 40 to 90% by weight of units derived from terephthalic acid and hexamethylenediamine, a2) from 0 to 50% by weight of units derived from .epsilon.-caprolactam and a3) from 0 to 60% by weight of units derived from adipic acid and hexamethylenediamine, components a2) and/or a3) accounting in total for not less than 10% by weight of the total number of units, B) 1-30% by weight of a brominated polystyrene or a brominated styrene oligomer or of a mixture thereof, C) 1-15% by weight of a synergistic metal oxide or metal borate or a mixture thereof and in addition D) 0-60% by weight of a fibrous or particulate filler or a mixture thereof and E) 0-20% by weight of an elastomeric polymer.

Description

X0~39~3~
- O. Z . 0050/40g71 Flameproofed thermoplastic molding materials The present invention relates to flameproofed thermoplastic molding materials containing, as essential components, A) 10-98~ by weight of a partly aromatic copolyamide, essentially composed of a1) from 40 to 90~ by weight of units derived from terephthalic acid and hexamethylenediamine, a2) from 0 to 50% by weight of units derived from ~-caprolactam and a3) from 0 to 60% by weight of units derived from adipic acid and hexamethylenediamine, components a2) and/or a3) accounting in total for not less than 10% by weight of the total number of units, B) 1-30% by weight of a brominated polystyrene or a brominated styrene oligomer or of a mixture thereof, C) 1-15% by weight of a synergistic metal oxide or metal borate or a mixture thereof and in addition D) 0-60% by weight of a fibrou or particulate filler or a mixture thereof and E) 0-20% by weight of an elastomeric polymer.
The present invention furthermore relates to the use of these molding materials for the production of moldings, and to the moldings obtainable U5 ing these molding materials as essential components.
Partially crystalline, partly aromatic copoly-amides pos e 8 in particular high thermal s~ability, which i~ necessary for many application Because of ~he high melting point, flameproofing the~e polyamides presents problems since most conventional flameproofing agents have poor thermal stability and therefore cannot be incorporated without decomposition.
EP-A 299 444 disclose~ that nylon 66/6T and nylon 6/6T can be flameproofed with red phosphorus in the presence of stabilizers.

.
' :':

99~

- 2 - O.Z. 0050/40971 Molding materials of this type have the disadvan-tage tha~, owing to the intrinsic red color of the phos-phorus and its pigment-like character, these molding materials cannot be given a paler color. In addition, 5the action of moisture and heat results in the formation of thermal oxidation products of phosphorus, such as phosphinic acids or oxyacids, which in turn present toxicological problems and on the other hand form conduc-tive deposits. The reduced surface resistance greatly 10restrict the suitability of such moldings in the electri-cal sector.
DE-A 27 03 419 discloses polyamide molding mater-als which are flameproofed with brominated styrene oligomers and a synergistic metal oxide.
15DE-A 15 70 395, DE-A 24 59 062 and DE-A 33 37 223 disclose the use of high molecular weight polystyrenes, brominated in the nucleus, as flameproofing agents for polyolefins, epoxy resins, styrene polymers, ABS and polyester molding materials.
20Thermoplastic polyamides, especially those having ` a high melting point, such as nylon 6/6T, are usually processed at above 300C. Particularly in the case of filler-reinforced polyamides, relatively high processing temperatures must be used. Furthermore, relatively high 25shear forces occur during incorporation of fillers, said shear forces resulting in further temperature i~creases, particularly local temperature peaXs, for example on the glass fiber kneading block.
However, most of the known halogen-based flame-30proofing agents decompose at these temperatures, and corrosive gase~ may form and the moldings become dis-colored. Another disadvantage is that many halogen com-pounds, such a~ chlorina~ed or brominated aliphatic, cycloaliphatic or aromatic low molecular weight com-35pound~, are highly toxic. Because of the poor compat-ibility of most low molecular weight halogen compounds with polyamides and their relatively high vapor pressure, - "` 20~

- 3 - O.Z. 0050/40971 exudation of the flameproofing agents and hence the formation of deposits may occur.
It is an object of the present invention to pro-vide flameproofed thermoplastic molding materials whose moldings have good electrical properties, in particular creep resistance and dielectric strength, and a good overall spectrum of mechanical properties. In addition, these moldings shoul~ have a pale intrinsic color and the flameproof properties and electrical properties should be ve.ry substantially independent of the type and amount of fillers.
We have found that this ob~ect is achieved, according to the invention, by the thermoplastic molding materials defined at the outset.
Preferred materials of this type and their use are described in the subclaim~.
The novel thermoplastic molding materials con-tain, as component A), from 10 to 98, preferably from 35 to 97, in particular from 40 to 90, % by weight of a partly aromatic copolyamide having the composition des-cribed below.
The partly aromatic copolyamide~ A) contain, as component al), from 40 to 90 ~ by waight of units derived from terephthalic acid and hexamethylenediamine. A small amount of the terephthalic acid, preferably not more than 10% by weight of the total amount of aromatic dicarbox-ylic acids u~ed, may be replaced by iqophthalic acid and other aromatic dicarboxylic acids, preferably those in which ~he carboxyl groups are in the para position.
In addition to the units derived from tereph-thalic acid and hexamethylenediamine, the partly aromatic copolyamide~ contain units derived from e-caprolactam (az) and/or units derived from adipic acid and hexameth-ylenediamine (a3).
The amount of units derived from ~-caprolactam is not more than 50, preferably from 20 to 50, in particular from 25 to 40, % by weight, while the amount of units ,:
: ;
' - s .~

' ' .

2~
.
- _ 4 - O.Z. 0050/40971 derived from adipic acid and hexamethylenediamine is not more than 60, preferably from 30 to 60, in particular from 35 to 55, % by weight.
The copolyamides may furthermore contain both units of ~-caprolactam and units of adipic acid and hexa-methylenediamine; in this case, it should be ensured that the amount of units which are free of aromatic groups is not less than 10, preferably not less than 20, % by weight. The ratio of units derived from ~-caprolactam to those derived from adipic acid and hexamethylenediamine is not subject to any particular restriction.
Preferred copolyamides are those whose composi-tion lies, in the ternary diagram, within the pentagon fixed by apices X1 to X5, which are defined as follows:
X1 40% by weight of units a1) 60% by weight of units a3) X2 60~ by weight of units a1) 40% by weight of units a3) X3 80~ by weight of units a1) 5~ by weight of units a2) 15% by weight of units a3) X4 80% by weight of units al) 20~ by weight of uni~s a2) X5 50% by weight of units a1) 50~ by weight of units a2) In the Figure, the pentagon fixed by these points is shown in a ternary diagram.
Polyamide~ containing from 50 to 80, in par-ticular from bO to 75, ~ by weight of units derived from terephthalic acid and hexamethylenediamine (units al)) and from 20 to 50, preferably from 25 to 40, ~ by weight of units derived from ~-caprolactam (unit~ a2)) have proven particularly advantageous for many intended uses.
In addition to the units a1) to a3) described above, the novel partly aromatic copolyamide~ may fur-thermore con~ain minor amounts, preferably not more than 15, in particular not more than 10, ~ by weight of ~ 99~
- 5 - o.Z. 0050/40971 further polyamide building blocks, as known from other polyamides. These building blocks may be derived from dicarboxylic acids of 4 to 16 carbon atoms and aliphatic or cycloaliphatic diamines of 4 to 16 carbon atoms and from aminocarboxylic acids or corresponding lactams of 7 to 12 carbon atoms. As suitable monomers of these types, suberic acid, azelaic acid, sebacic acid and isophthalic acid are mentioned here merely as typical dicarboxylic acids, 1,4-butanediamine, 1,5-pentanediamine, piperazine, 4,4~-diaminodicyclohexylmethane, 2,2-(4,4'-diaminodi-cyclohexyl)-propane and 3,3'-dimethyl 4,4'-diaminodi-cyclohexylmethane as typical diamines, and capryllactam, enantholactam, omega-aminoundecanoic acid and laurolactam as typical lactams and aminocarboxylic acid~
respectively.
The melting points of the partly aromatic co-polyamides A) are from 260 to more than 300-C, this high melting point also being associated with a high glass transition temperature of, as a rule, more than 75C, in particular more than 85C.
Binary copolyamides based on terephthalic acid, hexamethylenediamine and 6-caprolactam contain about 70%
by weight of units derived from terephthalic acid and hexamethylenediamine, melting points of about 300C and a glass transition temperature of more than 110C.
Binary copolyamides based on terephthalic acid, adipic acid and hexamethylenediamine (HMD) reach melting points of 300~C or more with lower contents of only about 55% by weight of unit~ of terephthalic acid and hexameth-ylenediamine, the glass transition temperature not beingquite so high as in the case of binary copolyamide~ which contain e-caprolactam instead of adipic acid or adipic acid/HMD.
The partly aroma~ic copolyamides A) can be prep-ared, for example, by the process described in EP-A 129 195 and EP A 129 196.
In thi~ process, an aqueous solution of monomers, `, :

;~ 39~
- 6 - O.Z. 0050~40971 ie. in this case the monomers which form the units a1) to a3), is heated to 250-300C under superatmo~pheric pres-sure-with simultaneous evaporation of water and formation of a prepolymer, the prepolymer and vapors are then con-tinuously separated, the vapors are rectified and the entrained diamine3 are recycled. Finally, the prepolymer is passed into a polycondensation zone and is subjected to polycondensation under superatmospheric pressure of from 1 to 10 bar and at from 250 to 300C. In this process, it is essential tha~ the aqueous salt solution is hea~ed under superatmospheric pressure of from 1 to 10 bar during a residence tLme of less than 60 seconds, the conversion advantageously being not less than 93% and the wa~er content of the prepolymer not more than 7~ by weight on emergence from the evaporator zone.
As a result of these short residence times, the formation of txiamines is substantially prevented~ so that the partly aromatic copolyamides A) generally have triamine contents of, preferably, less than a . 5, in particular less than 0.3, ~ by weight. High triamine contents can lead to a deterioration in the product quality and to problems during continuous preparation of the partly aromatic copolyamides. A particular example of a triamine which can cause such problems i~ dihexa-methylenetriamine, which is formed from the hexameth-ylenediamine used as a monomer.
The aqu~ous solutions used have, as a rule, a monomer content of from 30 to 70, in particular from 40 to 65, ~ by weight.
The aqueous salt solution is passed, advan-~ageously at from 50 to 100C, continuously into an evaporator zone, where the aqueous salt solution is heated to 250-330C under superatmospheric pressure of from 1 to 10, preferably from 2 to 6, bar. The tempera-ture used is of course above the melting point of the particular polyamide to be prepared.
As stated above, it is essential that the " ': ' ' Q~L9~
- 7 - O.Z. 0050/40971 residence time in the evaporator zone is not more than 60, preferably from lO to 55, in particular from 10 to 40, seconds.
The conversion on emergence from the evaporator zone i5 advantageously not less than 93%, preferably from 95 to 98%, and the water content is preferably from 2 to 5, in particular from 1 to 3, % by weight.
The evaporator ~one is advantageously in the form of a tube bundle. Tube bundles in which the cross-section of the individual tubes is alternately tubularand slot-like have proven particularly useful.
As a rule, a residence time of from 1 to 15 minutes is maintained in the mass transfer zone. The mass transfer zone is advantageously in the form of a tube bundle.
The two-phase vapor/prepolymer mixture emerging from the evaporator or mass tran fer zone is separated.
Separation i8 effected as a rule automatically on the basis of the physical differences in a vessel, the lower part of the ves el advantageously being in the form of a polymerization zone. The vapors liberated essentially consist of steam and diamines, which were liberated on evaporation of the water. These vapors are passed into a column and rectified. Examples of ~uitable columns are packed columns, bubble tray columns or sieve tray columns having from 5 to 15 theoretical plates. The column is advantageously operated under pres~ure condition~ identi-cal to tho~e in the evaporator zone. The diamines present in the vapors are separated off and recycled to 39 the evaporator zone. It is al50 possible ~o feed the di-amines to the downstream polymerization zone. The rectified steam obtained is taken off at the top of th~
column.
The resulting prepolymer, which, depending on its conversion, esQentially consi8t8 of low molecular weight polyamide and may contain re~idual amounts of unconverted salts and as a rule has a relative vi=cosity of from 1.2 ..
, 9~

- 8 - 0.2. 0050/40971 to 1.7, is passed into a polymerization zone. In the polymerization zone, the melt obtained is subjected ~o polycondensation at from 250 to 330C, in particular from 270 to 310C, and under superatmospheric pressure of from 1 to 10, in particular 2 to 6, bar. Advantageously, the vapors liberated here are rectified together with the abovementioned vapors in the column, a residence time of from 5 to 30 minutes advantageously being maintained in the polycondensation zone. The polyamide thus obtained, which as a rule has a relative viscosity of from 1.2 to 2.3, is removed continuously from the condensation zone.
In a preferred procedure, the polyamide thus obtained is passed in molten form through a discharge zone with simultaneous removal of the r~sidual water present in the melt. Examples of suitable discharge zones are devolatilization extruders. The melt freed from water in this manner is then extruded and the ex-trudates are granulated. The granules obtained are advantageously subjected to ~olid-phase condensation by means of superheated steam at below the melting point, for example from 170 to 240C, until the desired viscos-ity is obtained. The steam obtained at the top of the column is advantageously used for thi3 purpose.
The relative visco~ity, measured in 1% strength solution ~1 g/100 ml) in 96~ strength by weight H2SO4 at 23C, is in general from 2.2 ~o 5.0, preferably from 2.3 to 4.5, after the solid-phase postcondensation.
In another preferxed procedure, the polyamide melt discharged from the polycondensation zone is passed into a further polycondensation zone, where it is sub jected to condensation with continuous formation of new surfaces at from 285 to 310C, advantageously under reduced pressure, for example from 1 to 500 mbar, until the desired visco~ity is obtained. Suitable apparatuses are known as finishers.
Another proce~s which is similar to the one described above is de~cribed in EP-A 129 196, to which -~ - 9 - O.Z. 0050/40971 reference may be made for further details of the process.
The novel molding materials contain, as component B), 1-30, preferably '-25, in particular 1-20, % by weight of a brominated polystyrene or of a brominated styrene oligomer or of a mixture thereof.
The brominated oligostyrenes used as flameproof-ing agents have a mean degree of polymerization (number average) of from 3 to 90, preferably from 5 to 60, measured by vapor pressure osmometry in toluene. Cyclic oligomers are also suitable. In a preferred embodiment of the invention, the brominated oligomeric styrenes to be used are of formula I below, where R is hydrogen or an aliphatic radical, in particular alkyl, eg. CH3 or CzH5~
and n is the number of repeating building blocks in the chain. R' may be H, bromine or a fragment of a conven-tional free radicai initiator:

R~ CH2 1 --CH2 CH2-R
R R n R
n may be 1-88, preferably 3-58. The brominated oligostyrenes contain from 40 to 80, preferably from 55 to 70, % by weight of bromine. A product which predom-inantly consists of polydibromostyrene is preferred. The substances can be melted wi~hout decomposition and are soluble in, for example, tetrahydrofuran. They can be prepared either by bromination of the nucleus of styrene oligomers which may be aliphatically hydrogena~ed, as obtained, for example, by thermal polymerization of styrene (according to German Laid-Open Application DOS
2,537,385) or by free radical oligomerization of suitable brominated ~tyrenes. The flameproofing agent can also be prepared by ionic oligomerization of styrene and subse-quent bromination. The amount of brominated oligo tyrene required for flameproofing the polyamides depends on the :

.:
.

2~9~
- 10 - O.Z. 0050/40971 bromin~ content. The bromine content of the novel mold-ing materials is from 4 to 20, preferably from 5 to 12, by weight.
The brominated polystyrenes according to the invention are usually obtained by the process described in EP-A 47 549:

-tCH-CH rtn -~CH-CH 2-tn~

Ib + 3BrCI CH2--CH2 ~Br3+3HCI
(Il) Cl Cl (III) The brominated polystyrenes obtainable by this process and commercially available are predominantly tribromin-ated products substituted in the nucleus. n' (cr. III) is generally from 125 to 1,500, corresponding to a molecular weight of from 42,500 to 235,000, preferably from 130,000 to 235,000.
The bromine content (based on the content of bromine substitu~ed in the nucleus) is in general not less than 55~ preferably not less than 60, in particular 65, % by weight.
The commercial powder products generally have a glass transition temperature of from 160 to 200C.
It is also possible to use mixtures of the bro-minated oligostyrenes with brominated poly tyrenes in thenovel molding materials, any mixing ratio being possible.
The novel molding materials contain, a~ component C), 1-15, preferably 1-10, in particular 2-5, % ~y weight of a ynergistic matal oxide or metal borate or a mixture thereof. In general, zinc oxide, lead oxide, iron oxide, alumina, tin oxide and magnesium oxide or mixtures there-of are suitable as synergistic metal oxides. ~ntimony trioxide and/or antimony pentoxide are preferred.
Suitable metal borates are borates of metals of main group~ 1 to 3 and of subgroups 1 to 8 of the Periodic Table, anhydrous zinc bor te or zinc borate of . ` '.

Z~1~9~Æ
O. Z . 0050/40g71 the general formula (IV) 2ZnO3BzO3 x H2O (IV) where x is from 3.3 to 3.7 being preferred. This zinc borate is essentially stable at high processing tempera-tures of the partly aromatic polyamides and does not tendto eliminate the water of hydration to any significant extent. Accordingly, zinc borates having a high content of water of hydration are generally not so suitable as synergistic aqents.
It is also possible to use mixtures of metal borates with metal oxides, any mixing ratio being possible.
Mixtures of antimony trioxide with anhydrous zinc borate are preferred.
The novel molding materials may contain, as com-ponent D), not more than 60, preferably from 5 to 50, %
by weight of fibrous or particulate fillers or of a mix-ture thereof. Examples of fillerY are asbestos, carbon fibers or glass fibers in the form of woven glass fab-rics, glass mats or glass rovings, glass spheres and wollastonite.
Preferred fibrous reinforcing substances (com-ponent D~ are carbon fibers, po~assium titanate whiskers, Aramid fibers and particularly preferably glass fibers.
When glass fibers are used, they may be treated with a size and an adhesion promoter for better compatibility with the thermoplastic polyamide (A). In general, the glass fibers used have a diameter of from 6 to 20 ~m.
These glass fibers may be incorporated both in the form of short glass fibers and in the form of rovings.
In the finished injection molding, the mean length of the glass fibers i~ preferably from 0.08 to 0.5 mm.
Suitable particulate fillers are amorphous silica, asbestos, magnesium carbonate (chalk), powdered quart7, mica, talc, feldspar and in particular calcium silicates, such a~ wollastonite and kaolin (in particular calcined kaolin).

' , 3~4 - - 12 - O.Z. 0050/40971 Surprisingly, the novel molding materials have, as desired, classification V-O according to UL 94, even with high contents of particulate fillers.
Preferred combinations of fillers are, for 5example, 20% by weight of glass fibers with 15% by weight of wollastonite and 15~ by weight of glass fibers with 15% by weight of wollastonite.
As a further component E), a rubber Lmpact modifier (elastomer) may be present in the novel thermo-10plastic molding materials, in amounts of not more than 20, preferably from 1 to 10, % by weight.
Elastomers based on ethylene, propylene, buta-diene or acrylates or mixtures of these monomers may be mentioned merely as examples of rubber impact modifiers.
15Polymers of this type are described in, for exam-ple, Houben-Weyl, Methoden der organischen Chemie, Vol.
14/1 (Georg-Thieme-Verlag, Stuttgart, 1961), pages 392-406, and in the monograph by C.B. Bucknall, Toughened Plastics (Applied Science Publishers, London, 1977).
20Some preferred types of such elastomers are des-cribed below.
A first preferred group comprises the ethylene/
propylene (EP) and ethylene/propylene/diene (EPDM) rubbers, which prefarably have a ratio of ethylene radi-25cals to propylene radical~ of from 40 : 60 to 65 : 35.
The Mooney viscosities (MLI+4/100C) of such non-crosslinked EP and EPDM rubbers (gel contents generally less than 1% by weight) are preferably from 25 to 100, in particular from 35 to 90 (measured using the large rotor 30after a running tLme of 4 minutes at 100C according to DIN 53,523).
EP rubbers generally have virtually no double bonds, whereas EPDM rubbers may have from 1 to 20 double bonds per 100 carbon atoms.
35Exæmples of diene monomers for EPDM rubbers are conjugated dienes, such as isoprene and butadiene, nonconjugated diene~ of 5 to 25 carbon atoms, such as , ` - Z~9~9~
- 13 - O.Z. 0050/4097~
1,4-butadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene and 1,4-octadiene, cyclic dienes, such as cyclopentadiene, cyclohexadiene, cycloocatdiene and dicyclopentadiene, and alkenylnorbornenes, such as 5-ethylidene-2-norbornene, 5-butylidene 2-norbornene, 2-methallyl-5-norbornene and 2-isopropenyl-5-norbornene, and tricyclodienes, such as 3-methyltricyclo-[5.2.1Ø2.6]-3,8-decadiene, or mixtures thereof. 1,5-Hexadiene, 5-ethylidenenorbornene and dicyclopentadiene are preferred. The diene content of EPDM rubbers is preferably from 0.5 to 10, in particular from 1 to 8, %
by weight, based on the total weight of the rubber.
EP and EPDM rubbers can also be grafted with reactive carboxylic acids or their derivatives. Acrylic acid, methacrylic acid and their derivatives and maleic anhydride may be mentioned here merely as typical examples.
Another group of preferred rubber~ comprises copolymers of ethylene with acrylates and/or meth-acrylates, in particular those which additionally containepoxy groups. These epoxy groups are preferably incor-porated in the rubber by adding to the monomer mixture the epoxy-containing monomers of the general formula Y or VI

CHR3=CH--(CH~) ~(CtlR2) --CH--CHRl (V) m n CHR4=CR5--CO~(CH2) --CH--CHR6 (VI) where Rl, R2, R3, R4, R5 and R6 are each hydrogen or alkyl of 1 to 6 carbon atoms, m is an integer of from 0 to 20, n is an integer of from 0 to 10 and p is an integer of from 0 to S.
Preferably, Rl, R2 and R3 are each hydrogen, m is O or 1 and n is 1. The corresponding compound~ are alkyl , 9~
- 14 - O.Z. 0050/4~971 glycidyl ethers or vinyl glycidyl ethers.
Preferred examples of compounds of the formula (VI) are epoxy-containing esters of acrylic acid and/or methacrylic acid, of which glycidyl acrylate and glycidyl methacrylate are particularly preferred.
The ethylene content of the copolymers is in general from 50 to 98% by weight, and the amount of epoxy-containing monomers and the amount of acrylate and/or methacrylate are each from 1 to 49% by weight.
lQ Particularly preferred copolymers are those con-sisting of from 50 to 98.9, in particular from 60 to 95, % by weight of ethylene, from 0.1 to 40, in particular from 2 to 20, % by weight of glycidyl acryla~e, glycidyl methacrylate, acrylic acid and/or maleic anhydride, and from 1 to 45, in particular from 10 to 35, ~ by weight of n-butyl acrylate and/or 2-ethylhexyl acrylate.
Other preferred ester of acrylic and/or meth-acrylic acid are the methyl, ethyl, propyl, isobutyl and tert-butyl esters.
Vinyl esters and vinyl ethers may also be used as comonomers.
The ethylene copolymers described above can be prepared by conventional processes, preferably by random copolymerization under superatmospheric pres~ure at elevated temperatures. Corre ponding processes are des-cribed in the literature.
The melt flow index of the ethylene copolymers is in general from 1 to 80 g/10 min (measured at 190C and under a load of 2.16 kg).
Other preferred elastomers (rubbers) E) are graf~
copolymers with butadiene, butadiene/styrene, butadiene/
acrylonitrile and acryla~es, as described in, for example, DE-A-16 94 173 and DE-A~23 43 377.
Particular examples of the~e are the ABS
polymer~, as de~cribed in DE-A-20 35 390, DE-A-22 48 242 99~
- 15 - O.Z. 0050/40971 and EP-A-22 216, those stated in EP-A-22 216 being par-ticularly preferred.
Other suitable rubbers E) are graft polymers of from 25 to 98% by weight of an acrylate rubber having a S glass transition temperature of less than -20C, as the grafting base, and from 2 to 75~ by weight of a copolymerizable ethylenic-ally unsaturated monomer whose homopolymers and copoly-mers have a glass transition temperature of more than 25C, as the graft.
The grafting bases are acrylate or methacrylate rubbers, and up to 40% by weight of further comonomers may be present. The C1-C8-esters of acrylic acid or methacrylic acid and their halogenated deriva~ives, as well as aromatic acrylates and mixtures thereof, are preferred. Acrylonitrile, methacrylonitrile, styrene, ~-methylstyrene, acrylamides, methacrylamides and vinyl~Cl-C6-alkyl ethers may be mentioned as comonomers in the grafting base.
The grafting base may be noncrosslinked or par-tially or completely crosslinked. Crosslinking is achieved by copolymerization of, preferably, from 0.02 to 5, in particular from 0.05 to 2, % by weight of a cross-linking monomer having more than one double bond. Suit-able crosslinking monomers are described in, for example, DE-A-27 26 256 and EP-A-50 265.
Preferred crosslinking monomers are ~riallyl cyanurate, triallyl isocyanurate, triacryloylhexahydro-s-triazine and trialkylbenzene~.
If the crosslinking monomers^have more than 2 polymerizable double bonds, it is advantageous to re~-trict their amount to not more than 1% by weight, based on the grafting base.
Particularly preferred gxafting bases are emul-sion polymers having a gel content of more than 60% by weigh~ (detenmined in dLmethylformamide at 25C according , 9~
- 16 - O.Z. 0050/40971 to M. Hoffmann, H. Kromer and R. Kuhn, Polymeranalytik, Georg-Thieme-Verlag, Stuttgart 1977).
Other suitable grafting bases are acrylate rubbers having a diene core, as described in, for example, 5EP-A-50 262.
Particularly suitable graft monomers are styrene, ~-methylstyrene, acrylonitrile, methacrylonitrile and methyl methacrylate and mixtures thereof, in particular those of styrene and acrylonitrile in a weight ratio of 10from 90 : 10 to 50 : 50.
The grafting yield, ie. the quotient of the amount of grafted monomer to the amount of graft monomer used is in general from 20 to 80%.
Rubber~ based on acryla~es, which may be used 15according to the invention, are described in, for example, DE-A-24 44 584 and DE-A-27 26 256.
The rubbers E) preferably have a glass transition temperature of less than -30C, in particular less than -40C, which leads to good impact strength even at low 20temperatures.
It is of course also possible to use mixtures of the abovementioned elastomers which impart Lmpact strength.
In addition to components A) to E), the novel 25molding materials may contain conventional additives and processing assistants. The amount of these is in general not more than 20, preferably not more than 10, % by weight, based on the total weight of componen~s A) to E).
Example3 of conventional additives are stabil-30izers and antioxidants, heat stabilizer~ and W stabil-izers, lubricants and mold release agents, colorants, such as dyes and pigment~, nucleating agents and plas-ticizers.
Antioxidants and heat stabilizers which may be 35added to the thermoplastic materials according to the invention are, for example, halides of metals of Group I
of the Periodic Table, for example sodium halides, :

2~9~
- - 17 - O.Z. 0050/40971 potassium halides and lithium halides, if necessary in combination with copper(I) halides, eg. chlorides, bromides or iodides. Sterically hindered phenols, hydroquinones, substituted members of this group and mixtures thereof may also be used, preferably in concen-trations of not more than l~ by weight, based on the weight of the molding material.
Examples of W stabilizers are various subs-tituted resorcinols, salicylates, benzotriaæoles and benzophenones, which are used in general in amounts of not more than 2.0% by weight.
Lubricants and mold release agents, which are added as a rule in amounts of not more than 1% by weight to the thermopla3tic material, are ~tearic acid, stear-ates, stearyl aclohol, alkyl stearates and stearamides,a~ well as esters of pentaerythritol with long-chain fatty acids.
The additive$ include stabilizers which prevent dehydrobromination of component B), so that the process-ing stability i~ increa~ed and the corrosion effectdecreased. Such stabilizers are, for example, salts of mono- or bifunctional fatty acid , such as calcium behenate, calcium st~arate, barium stearate and lead phthalate, calcium carbonate, organic tin compounds, such as cyclic dibutyltin sulfide or butylthiostannous acid and hydrogen phosphates, eg. Na2HPO4.
~ he novel molding materials can be prepared by conventional processes, by mixing the starting components in a conventional mixing apparatus, ~uch as an extruder, a Bxabender mill or a Banbury mill, and then extruding the mixture. After extrusion, the extrudate i~ cooled and comminuted. The mixing temperature~ are in general from 280 to 350C.
It i9 in principle also possible, and sometimes advantageous, first to mix the low molecular weight com-ponent A) with B~ and C) and, if necessary, D) and E) and ~hen to carry out solid-phase postcondensation.

- 18 - O. Z . 0050/40971 It may also be advantageous to incorporate the synergistic agents in the form of a masterbatch of poly-~mide or polyethylene.
The nov~l molding materials have a good overall spectrum of mechanical properties. The mol~ings have a pale intrinsic color and are toxicologLcally acceptable in use. In addition to the good flame resistance, they have good electrical properties, in particular good creep resistance and dielectric strength. Because of the extremely good stability to various soldering processes, the novel molding materials are particularly suitable for the production of injection molded circuit boards, which may also contain integrated functional elements and may be readily copper-plated.
The novel molding materials are also suitable for the production of, in particular, compact housings and other components for electronic equipment, high require-ments being set for the heat distortion resistance.
EXAMPLES
The following components were used:
Component A) The preparation was carried out according to EP
129 195.
An aqueous solution, consisting of 35 kg of ~-caprolactam, 55 kg of terephthalic acid and 38.5 Xg of hexamethylenediamine and 128.5 kg of water, wa~ con~eyed from a heated storage container at about 80C at a rate corresponding ~o an amount o polyamide of 5 kg/hour, by means of a metering pump, into a tubular evaporator arranged partly horizontally and partly vertically. The evaporator wa3 heated by means of a liquid heating medium, which wa~ at 295C, with vigorous circulation.
The evaporator had a length of 3 m, a capacity of 180 ml and a heat-transfer surface area of about 1300 cm2. The residence time in the evaporator was 50 econds. The prepolymer/steam mixture emerging from the evaporator wa~
at 290C and was separated into steam and melt in a :: z~
- 19 - O.Z. 0050/40g71 separator. The melt remained in the separator for a further 10 minutes and was then extruded by means of an extruder hav~ng a devolatilization zone, and the extru-date was solidified in a water bath and then granulated.
The separator and the evaporator zone were kept under a pressure of 5 bar by a pressure regulating means arranged downstream of the column. The steam separated of in the separator was fed to a packed column which had about 10 theoretical plates and into which about 1 1 of vapor condensate per hour was introduced at the top to generate a reflux. The resulting temperature at the top of the column was 152C. The steam emerging downstream of the let-down valve was condensed, and it contained less than 0.05~ by weight of hexamethylenediamine and less than 0.1% by weight of ~-caprolactam. An aqueous solution of hexamethylenediamine, which contained 80% by weight of hexamethylenediamine and from 1 to 3% of ~-caprolactam, based in each case on polyamide produced, wa~ obtained as a bottom product of the column. This solution was added to the starting salt solution again by means of a pump before ~he starting salt solution entered the evaporator.
Downstream of the evaporator, the prepolymer had a relative viscosity of 1.25, measured in 96% strength by weight sulfuric acid at 20C and, according to terminal group analysi~, had a conversion of from 93 to 95%. The content of bishexamethylenetriamine was from 0.1 to 0.15%
by weight, based on polyamide.
After emergence of the polymer melt from the separator, the polyamide had a very pale intrinsic color and an extremely low content of bi3hexamethylenetriamine of 0.17% and a relative viscosity of from 1.65 to 1.80.
The product had roughly equivalent amounts of terminal carboxyl and amino groups.
The content of extractables (extraction with methanol) was from 3.1 to 3.3~ by weight.
In the extruder, the melt was then let down to atmospheric pressure and underwent virtually no further .

2 Ot~9~
, - - 20 - O.Z. 0050/40971 condensation during a residence time of less than 1 minute. The resulting granules were subjected to conti-nuous solid-phase condensation using superheated steam at 195C during a residence time of 30 hours until a final viscosity ~ rel of 2.50 was obtained. The content of extractables was then 0.2% by weight (methanol extract).
Component B) Brominated polystyrene having a bromine content (content of bromine substituted in the nucleus) of 67%
(Pyro-check~ 68 PB from Ferro Corporation) Component C) Antimony trioxide having a density of from 5.2 to 5.8 g/cm3 Component Dl) Glass fibers having a mean diameter of 10 ~m.
Component D2) Wollastonite having a median particle size (d50) of 10 ~m and a specific surface area of 5 m2/g.
Component E) An olefin copolymer of 59.8% by weight of ethylene, 35% by weight of n-butyl acrylate, 4.5% by weight of acrylic acid and 0.7% by weight of maleic anhydride, having a melt flow index MFI of 10 g/lO min at 190C and under a load of 2.16 kg.
This copolymer was prepared by copolym~rization of the monomers at elevated temperatures and under super-atmospheric pressure.
The components were mixed in a twin-screw extru-der at 300-350C, and the mixture wa~ extruded into a water bath. Component E) was added to the melt first.
After granulation and drying, th~ test specimen~ were produced on an injection molding machine and were tested.
The fire test was carried out according to UL 94 using 1/8, 1/16 and 1/32 inch te~t specimen~ with conven-tional conditioning. The LOI (lowe~t oxygen index) wa~

~9~

- 21 - O.Z. 0050/40971 determined according to ASTM D 2863-77.
The creep resistance was determined according to IE~ 112/1979, the modulus of elasticity according to DIN
53,457 and the impact strength according to DIN 53,453.
The composition of the molding materials and the results of the measurements are shown in the Table.

.' ' ; ' ' .

~9~
- 22 - O.Z. 0050/40971 o .~

o o o o o o o o o o o ~ æ co ~
X 0 ~ a~ co ~n co r~

oUl ~ o ~_ o ~ t~ O
~ ~ ~ el' ~ ~ ~r I
a) u, o o o o u~
O u~
U s~ _ U~
t` N IJ~ u-) O
H
O ~0 0 COCO
-1 ~ ~ ~C~

~ O O O O O
d'~ ~ I I I I
P ' P P P
h O 0~
O O O O O
P P ~ :~

S-l N
a~ o~
h t~ ~ O O O O O
:- ~ P P ~ ~
~0 U
S~ ~ lY 1.~ o ~ O~DO~
+ + +
~ I ~ U
~ ~a a aa aa U~ O Ul InUl U~
_. ~ H--i H
~ U U ~ C~ ~
~_1 a~
3 ~ ~ ~ ~ ~

a~ :q m ~ m ~ ~o o ~ U~ U~ ,., ~ ~

o ~ ,¢ aC ~¢ ~¢ C) ~ O~
O ~P N CO t~ eP E 1 O U~
o Z .-1 N tt~ ~ U'1 *

- -.
:: ~
: ,

Claims

1. A flameproofed, thermoplastic molding material containing, as essential components, A) 10-98% by weight of a partly aromatic copolyamide, essentially composed of a1) from 40 to 90% by weight of units derived from terephthalic acid and hexamethylenediamine, a2) from 0 to 50% by weight of units derived from .epsilon.-caprolactam and a3) from 0 to 60% by weight of units derived from adipic acid and hexamethylenediamine, components a2) and/or a3) accounting in total for not less than 10% by weight of the total number of units, B) 1-30% by weight of a brominated polystyrene or a brominated styrene oligomer or of a mixture thereof, C) 1-15% by weight of a synergistic metal oxide or metal borate or a mixture thereof and in addition D) 0-60% by weight of a fibrous or particulate filler or a mixture thereof and E) 0-20% by weight of an elastomeric polymer.

2. A flameproofed thermoplastic molding material as claimed in claim 1, containing 35-97% by weight of A), 1-20% by weight of B), 1-10% by weight of C) and 1-35% by weight of D).

3. A flameproofed thermoplastic molding material as claimed in claim 1, containing 25-87% by weight of A), 1-20% by weight of B), 1-10% by weight of C), 10-35% by weight of D) and 1-10% by weight of E).

- 24 - O.Z. 0050/40971

4. A flameproofed thermoplastic molding material as claimed in claim 1, wherein the partly aromatic copoly-amides A) have a triamine content of less than 0.5% by weight.

5. A flameproofed thermoplastic molding material as claimed in claim 1, wherein the component A) is composed of a1) from 50 to 80% by weight of units derived from terephthalic acid and hexamethylenediamine and a2) from 20 to 50% by weight of units derived from .epsilon.-caprolactam.

6. A flameproofed thermoplastic molding material as claimed in claim 1, wherein the brominated polystyrene (component B) has a bromine content of not less than 55%
by weight.

7. A flameproofed thermoplastic molding material as claimed in claim 1, wherein the brominated styrene oligo-mer (component B) has a bromine content of not less than 40% by weight.

8. A flameproofed thermoplastic molding material as claimed in claim 1, wherein the component C) consists of antimony trioxide or zinc oxide or lead oxide or iron oxide or zinc borate or a mixture thereof.

9. A molding obtainable from a thermoplastic molding material as claimed in claim 1.