GB1584203A - Tetrabromophthalimide derivatives and their use as flameprroofing agents - Google Patents

Description

(54) TETRABROMOPHTHALIMIDE DERIVATIVES AND THEIR USE AS FLAMEPROOFING AGENTS (71) We, DYNAMIT NOBEL AKTIENGESELLSCHAFT, a German Company of 521 Troisdorf bes Koln, Postfach 1209, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to tetrabromophthalimide derivatives and to their use as flameproofing agents.

According to one aspect of the invention, the tetrabromophthalimide derivatives of the invention are bromine-containing ester imides having the general formula (I):

in which R represents a direct bond or a carboxyl-group-free radical derived from an aliphatic or aromatic, halogenated or halogen-free, mono-, di-, tri- or tetra- carboxylic acid, and n is 1, 2, 3 or 4.

Preferably, R is a radical derived from oxalic acid, fumaric acid, maleic acid, trimellitic acid, pyromellitic acid, ethane tricarboxylic acid, a brominated terephthalic acid, a brominated isophthalic acid, a brominated phthalic acid, a non-brominated isophthalic acid, or a non-brominated phthalic acid.

The invention also relates to the use of these substances as flameproofing agents for plastics, and to moulding compositions containing ester imides corresponding to formula (I) above.

The bromine-containing ester imides are esters of N-(ss-hydroxyethyl)- tetrabromophthalimide corresponding to structural formula (II) below with monobasic, dibasic, tribasic and tetrabasic, preferably monobasic or dibasic, carboxylic acids or ester-forming carboxylic acid derivatives:

The N-(ss-hydroxyethyl)-tetrabromophthalimide of formula (II) can be obtained from tetrabromophthalic acid anhydride and amonoethanol. The two reactants are reacted in a molar ratio of tetrabromophthalic acid anhydride to aminoethanol of preferably 1:1 in a solvent or solvent mixture, preferably o-dichlorobenzene, at temperatures in the range from +130 to -20 C and preferably at temperatures in the range from +110 to -100C, to form the imide intermediate, the amide carboxylic acid corresponding to structural formula (III) below

which is subsequently cyclodehydrated by increasing the temperature to 100 - 2200C and preferably to 150 - 1900C to form the N-(P-hydroxyethyl -tetrabromophthalimide of formula (II). It is of advantage to distill off water of reaction and, optionally, parts of the solvent.

For synthesising the amidocarboxylic acid of formula (III), either aminoethanol or tetrabromophthalic acid anhydride may be initially introduced and the other reactant added slowly while stirring. For forming (II), it is even sufficient to add the aminoethanol to a suspension of the tetrabromophthalic acid anhydride in an organic solvent or solvent mixture.

The esterification or transesterification of (II) with carboxylic acids or their derivatives is carried out at temperatures of from 150 to 220"C, preferably at temperatures of from 160 to 200"C, and at a molar ratio of from 0.9 to 1.1 mole of (II) per carboxyl group of the acid or derivative.

Basically, it is possible to use any carboxylic acids, although for practical reasons it is preferred to use short-chain aliphatic carboxylic acids containing from 2 to about 8 carbon atoms and aromatic carboxylic acids, particularly of the benzene series, containing from 7 to 12 carbon atoms or derivatives thereof. It is possible to use both unsaturated and also saturated carboxylic acids and their ester-forming derivatives, particularly the anhydrides, or lower alkyl esters, of which the methyl or ethyl ester is preferred, and also mixtures of the above-mentioned substances.

Preferred acid components are benzoic acid, fumaric acid or their dimethyl or diethyl esters; maleic acid or its anhydride; oxalic acid diethyl ester; 1,1,2-ethane tricarboxylic acid or its trimethyl ester; 1,2,2,3-propane tetracarboxylic acid or its tetramethyl ester; phthalic acid or its anhydride; tetrachlorophthalic acid or its anhydride; tetrabromophthalic acid or its anhydri de; hexachloroendo-methylene tetrahydrophthalic acid or its anhydride; terephthalic acid or its dimethyl ester; isophthalic acid or its dimethyl ester; trimellitic acid or its anhydride and pyromellitic acid or its anhydride.

It is particularly preferred to use benzoic acid in the form of its esters, oxalic acid and esters thereof and also terephthalic acid esters.

The esterification or transesterification of the above-mentioned acid components with the N-(B-hydroxyethyl)-tetrabromophthalimide is carried out under reaction conditions known per se. The reaction is carried out in a molar ratio which guarantees the equivalence of the alcoholic with the carboxylic acid functions within a tolerance of up to a 10 mole % excess of one of the two components, preferably in the presence of a solvent for at least one of the two reaction components and preferably in the presence of an esterification or transesterification catalyst under ester-forming reaction conditions. It is of advantage to use a high-boiling solvent which may also serve as entraining agent for the water of reaction formed and for the lower alcohol formed. Suitable catalysts are esterification or transesterification catalysts known per se, such as sulphuric acid, phosphoric acid, benzene orp-toluene sulphonic acid or Zn-acetate, Mn-acetate, germanium dioxide or titanic esters.

It is preferred to use the sulphonic acids, for example p-toluene sulphonic acid, for esterification reactions and the titanic esters, for example tetrabutyl titanate, or the product of transesterification between tetrabutyl titanate and 2-ethyl-1,3-hexane diol for transesterification reactions. The catalysts are best used in quantities of from 0.01 to 0.5% by weight and preferably in quantities of from 0.05 to 0.3% by weight, based on the sum total of the reaction components.

For economically producing the ester imides, it is of advantage that the intermediate product N(ss-hydroxyethyl)-tetrabromophthalimide does not have to be isolated and dried after its synthesis and reused for esterification with the polycarboxylic acids or their derivatives. Instead. the reaction with the acid component may be carried out immediately after cyclisation to form the N-(-hydroxyethyl)-tetrabromophthalimide.

Depending upon their structure. the bromine-containing ester imides are either obtained insoluble in suspended form during the actual esterification reaction or largely crystallise out on cooling to room temperature after termination of the reaction. In order to complete the yield and, optionally. also to obtain a smaller particle size of the ester imides, it is often of advantage to add a precipitant. preferably a liquid aliphatic hydrocarbon, such as petroleum ether or petrol. or a lower alcohol. such as methanol or ethanol. to the reaction mixture with rapid cooling and intensive stirring.

The ester imides are filtered off under suction. washed out with petroleum ether or methanol and dried. At 93 to 99% of the theoretical. the yield is substantially quantitative.

The ester imides are obtained in such pure form that they do not have to be purified for use as flameproofing agents.

According to another aspect of the present invention the tetrabomophthalimidc derivatives of the invention are bromine-containing acetalimides having the general formula (IV):

in R' is a direct bond or a phenylene group.

The bromine-containing acetalimides can be used as highly effective, non-chalking flameproofing agents for plastics. particularly for linear thermoplastic polyester resins. such as polytetramethvlene terephthalate.

The bromine-containing acetalimides of formula (IV) are derived as acetals from N-(B-hydroxyethyl)-tetrabromophthalimid corresponding to structural formula (II) above and a dialdehyde. e.g. glyoxal. terephthaldialdehyde. phthaldialdehyde or isophthaldialidehyde.

In the following. these substances are referred to in short as acetalimides of the particular dialdehydes.

The compound of formula II and its production have alreadv been described have.

Cyclisation of the amidocarboxvlic acid (III) to form the N-(l3-hydroxyethyl)tetrabromophthalimide (II) is followed by the reaction with the dialdehyde. Glyoxal is the dialdehyde preferably used for this purpose.

The temperature is preferably in the range from 100 to 2000C. The pressure is preferably normal pressure. although a slight excess pressure of up to about 5 bars may also be applied.

If the reaction of (II) with glyoxal or terephthal dialdehyde is carried out under the reaction conditions normally applied in the production of acetals. i.e. if the reactants N-(ss-hydroxyethyl)-tetrabromophthalimide and dialdehyde are heated in the presence of catalytic quantities of a strong acid. products which are unsuitable for use as flameproofing agents (FP-agents) are obtained. even if the water of reaction formed is removed. The reaction to form the acetal is incomplete. The product then contains the starting substance (II) and fairly large numbers of free hydroxyl groups are in evidence. The acetalimides thus produced have a wide melting range corresponding to their heterogeneous composition and poor thermal stability. Decomposition phenomena occur during their incorporation into high melting polyesters. resulting in discoloration of the compounds and in molecular weight degradation of the polyester. When the compounds are stored under heat (10"C), the flameproofing agent chalks out and the compound suffers a loss in weight.

Accordingly, it is preferred to carry out the reaction in the presence of an alcohol, since it has been found that the acetalimides of formula (IV) can readily be produced in highly pure form providing an alcohol is additionally present during the reaction of (II) with dialdehydes by the above-mentioned method. This alcohol does not enter into the global reaction equation and is only consumed in negligible quantities. Most of the alcohol is recovered together with the solvent and the entraining agent optionally used for removing the water of reaction.

Accordingly, the present invention also relates to a process for producing the bromine-containing acetalimides of formula (IV) by reacting tetrabromophthalic acid anhydride with aminoethanol to form the amidocarboxylic acid, cyclising the amidocarboxylic acid thus formed at 100 to 2200C to form N-(P-hydroxyethyl)tetrabromophthalimide (II) and subsequently reacting (II) with a dialdehyde (e.g. glyoxal, terephthal dialdehyde, phthal dialdehyde or isophthal dialdehyde) to form acetalimides of formula (IV) in a molar ratio of (II) to dialdehyde of from 4:1 to 4:1.4, optionally in the presence of an alcohol.

Suitable alcoholic components are straight-chain or branched aliphatic saturated alcohols with 2 to 8 carbon atoms, for example propanol, i-propanol, butanol, i-butanol, tert.-butanol, pentanol, hexanol, 2-ethyl hexanol, heptanol, octanol and also cyclohexanol.

It is preferred to use butanol. The alcohols are generally used in quantities of from 18 to 36% by weight, based on the reaction components.

Suitable solvents for the reaction are chlorinated hydrocarbons, such as trichloroethylene, perchloroethylene, hexachlorobutadiene, chlorobenzene, o-dichlorobenzene or trichlorobenzene and also mixtures thereof. The solvent preferably used is odichlorobenzene.

Aromatic hydrocarbons, such as benzene, toluene or xylene, may be used as entraining agents for removing the water of reaction formed during acetal formation. However, it is not absolutely necessary to use an entraining agent.

The molar ratio of the reactions used, N-(p-hydroxyethyl)-tetrabromophthalimide/ dialdehyde, is in the range from 4:1 to 4:1.4 and is preferably in the range from 4:1.1 to 4:1.3.

In the case of the aromatic dialdehydes, a molar ratio of 4:1 is preferably used on account of the fact that both components are substantially involatile.

The catalysts used for accelerating acetal formation are catalysts kown per se, particularly strong acids, such as sulphuric acid, phosphoric acid, benzene or p-toluene sulphonic acid or methane sulphonic acid. The sulphonic acids are preferably used.

The catalysts may be used in quantities of from 0.1 to 3% by weight, based on the reactants.

For economically producing the acetalimides, it is of advantage that the intermediate product, N-(B-hydroxyethyl)-tetrabromophthalimide does not have to be isolated and dried after its synthesis and reused for acetal formation with the dialdehydes. Instead, it is possible to add the dialdehyde components to the solution or suspension of the N-((3-hydroxyethyl)-tetrabromophthalimide formed after cyclodehydration and directly to carry out the acetal-forming reaction.

Depending upon their structure, the bromine-containing acetalimides are obtained insoluble in suspended form in the final phase of the actual acetal-forming reaction or largely crystallise out on cooling to room temperature after termination of the reaction. In order to complete the yield and, optionally, also to obtain a smaller particle size of the acetalimides, it is of advantage to add a precipitant for the reaction products, preferably a liquid hydrocarbon, such as petrol, to the reaction mixture with stirring during the actual cooling process. The acetalimides are filtered off under suction, washed out with petrol and dried. The substances are obtained in high yields of more than 90% in a purity which is sufficient for the proposed application so that they do not have to be subsequently purified.

As indicated above, the invention also provides a moulding composition comprising a polymeric material and a tetrabromophthalimide derivative of the invention. Examples of polymeric materials are addition polymers (e.g. vinyl homopolymers and copolymers); polycondensates (e.g. (a) thermoplastic linear high molecular weight polyesters such as polyethylene terephthalate and polytetramethylene terephthalate, (b) polycarbonates, (c) polyurethanes and (d) polyamides); and hardenable resins. The tetrabromophthalimide derivative is preferably present in an amount of from 3 to 20% by weight, more preferably from 5 to 15% by weight. The moulding composition may additionally include a synergistically acting substance, e.g. antimony trioxide.

The invention will now be illustrated by the following Examples. In the Examples, reference is made to the Underwriters Laboratories UL94 Test. In this Test, the terms V0, V1, V2 and V3 have the following meanings; V0 means that the average after-burning time of the test specimen is 5 seconds or less and that the highest after-burning time is not more than 10 seconds; V1 means that the average after-burning time is less than 25 seconds and that the highest after-burning time is not more than 30 seconds; V2 means that the after-burning time is less than 25 seconds but that dripping pieces of plastic result; and V3 means that the specimen is not self-extinguishing.

EXAMPLE 1 Production of an ester imide corresponding to structural formula (V)

In a reaction vessel equipped with a blade stirrer, dropping funnel and distillation bridge with a descending condenser, 232 g (0.5 mole) of tetrabromophthalic acid anhydride are suspended in 500 ml of o-dichlorobenzene. 30.5 g (0.5 mole) of ethanolamine are added dropwise over a period of 30 minutes with vigorous stirring and cooling in an ice bath. The resulting suspension of the amidocarboxylic acid of formula (III) is stirred for 1 hour and subsequently heated for 1 hour to 1800C for cyclodehydration. 150 ml of a mixture of water of reaction and o-dichlorobenzene are distilled off in 3 hours at temperatures of from 180 to 195"C. 48.25 g (0.25 mole) of terephthalic acid dimethyl ester- and 0.3 g of tetrabutyl titanate as transesterification catalyst are added to the resulting solution of the N-(ss-hydroxyethyl)-tetrabromophthalimide (formula II) in o-dichlorobenzene at a temperature 160 C, followed by transesterification at 180 to 195 C over a period of 4 hours, during which 100 ml of a mixture of methanol and o-dichlorobenzene were distilled off.

800 ml of petroleum ether were stirred into the reaction solution, thus precipitating the ester imide. After filtration under suction and repeated washing with petroleum ether, the product was dried first at room temperature and then in vacuo at a temperature increasing up to 2000C.

277.5 g of the powder-form, almost colourless ester imide are obtained. Yield 97%, based on tetrabromophthalic acid anhydride. Melting point 298 - 302"C.

The IR-spectrum shows absorption bands at 1765 em (v m (C=O) cycl. imide); 1705 cml (vas m (C=0); cyci. imide); 1720 cm' (v (C=0); ester); 1255 cm' (v (C-O); ester); 715 cm' (6(C); aromat.). Accordingly, the ester imide of structural formula (4) is present.

Elemental analysis: observed C 29.44 calculated C 29.37 H 1.15 H 1.04 N 2.49 N 2.44 Br 55.6 Br 55.9 The weight loss after storage under heat at 200 C amounts to 0.16% after 3 hours and to 0.34% after 24 hours. According to TGA (air atmosphere; heating rate 8 C/minute), the weight loss amounts to 1% at 3580C, to 5% at 383 C and to 10% at 3920C.

EXAMPLE 2 Production of an ester imide corresponding to structural formula (all)

In a reaction vessel equipped in the same way as described in Example 1, the suspension of the amidocarboxylic acid is produced as in Example 1 from 92.8 g (0.2 mole of tetrabromophthalic acid anhydride in 180 ml of o-dichlorobenzene with (0.2 mole of ethanolamine.

The resulting suspension of the amidocarboxylic acid is cyclised for 3 hours at 180 to 195"C, 30 ml of a mixture of water and o-dichlorobenzene being distilled off. After cooling to 1500C, 12.76 g (0.11 mole) furmaric acid, 0.16 g of cencentrated phosphoric acid as esterification catalyst and 0.08 g of triphenyl phosphite as antioxidant are added to the resulting solution of the N-(B-hydroxyethyl)-tetrabromophthalimide (structural formula II) in o-dichlorobenzene. This is followed by condensation for 4 hours at 180 to 1950C (bath temperature), approximately 25 ml of a mixture of water and o-dichlorobenzene distilling over. 250 ml of petroleum ether are added during the actual cooling process, the ester imide precipitated is filtered under suction at room temperature, washed out once with petroleum ether and twice with acetone and dried in air at up to 200"C. Yield. 103 g of powder-form, substantially colourless ester imide = 95%, based on the tetrabromophthalic acid anhydride. Melting point: 307 - 311"C.

According to the IR-spectrum which shows ester absorption bands at 1150 - 1250 cm~l (C-O-stretching vibrational band) and bands of the C=C-double bonds (v (C-H): 3060 cm', y (C-C): 1635 cm'; 5 (trans CH=CH): 970 cm'), the ester imide of structural formula (VI) is present.

Elemental analysis: observed C 26.46 calculated C 26.42 H 1.22 H 0.92 N 2.63 N 2.56 Br 58.8 Br 58.7 Weight loss at 200"C (air): 0.11% after 3 hours and 0.14% after 24 hours. The tempered sample does not show any visible change.

According to TGA (air atmosphere; heating rate 8"C/minute), the weight loss amounts to 1% at 315"C, to 5% at 365"C, to 10% at 380"C and to 20% at 3900C.

EXAMPLE 3 Production of an ester imide corresponding to structural formula (VII)

Following the procedure of Example 2, a solution of 101 g (0.2 mole) of N-(ss- hydroxyethyl)-tetrabromophthalimide in 150 ml of o-dichlorobenzene is produced, followed by the addition of 15 g (0.103 mole) of oxalic acid diethyl ester together with 0.2 g of the titanate of 2-ethyl-1.3-hexane diol.

The ester imide formed (after 4 hours) by transesterification at 175 to 1900C, during which ethanol is distilled off, partly precipitates in the form of a fine deposit during the reaction. Precipitation of the product is completed by adding 200 ml of petroleum ether.

Working up and drying are carried out in the same way as in Example 1. Yield: 104.5 g (97.4 C/c) of finely powdered, substantially colourless ester imide. Melting point 326 - 331"C.

IR-spectrum: strong bands for the imide (1700/1765 cam~') and ester functions (1730, 1180 elm ') of the ester imide of structural formula (VII).

There are no OH-valencies (starting material).

Elemental analysis: observed C 25.15 calculated C 24.81 H 0.90 H 0.75 N 2.63 N 2.63 Br 59.2 Br 60.1 Weight loss (in air at 200"C): 0.13% after 3 hours and 0.24% after 24 hours. The tempered sample does not show any visible change.

According to TGA (air atmosphere; heating rate 8"C/minute), the weight loss amounts to 1% at 312"C, to 5% at 3540C, to 10% at 3680C and to 20% at 3790C.

EXAMPLE 4 Production of an ester imide corresponding to structural formula (Vlil)

Following the procedure of Example 2, a solution of 101 g (0.2 mole) of N-(ss- hydroxyethyl)-tetrabromophthalimide in 150 ml of o-dichlorobenzene is prepared with the reactants tetrabromophthalic acid anhydride (92.8 g, 0.2 mole) and ethanolamine (12.2 g, 0.2 mole). 13.5 g (0.067 mole) of ethane-1,1,2-tricarboxylic acid trimethyl ester and 0.16 g of tetrabutyl titanate are added, followed by transesterification at a temperature increasing to 160 - 195"C (bath temperature). During the four-hour transesterification reaction, approximately 30 ml of a mixture of methanol and o-dichlorobenzene are distilled off. After cooling, the ester imide is precipitated with 400 ml of petroleum ether, followed by washing and drying in the same way as before.

Yield. 101.9 g (94%) of ester imide melting at 246 - 253"C. IR-spectrum: strong bands of the imide function (1705/1768 cam~1); ester carbonyl band as a shoulder (1728 cm' and (C-O): 1150 cam~') of the ester imide of structural formula (VIII).

Elemental analysis: observed C 25.91 calculated C 25.68 H 1.07 H 0.91 N 2.49 N 2.57 Br 57.9 Br 58.7 Weight loss (in air at 200"C): 0.28% after 3 hours and 0.82 % after 24 hours. A stored sample does not show any visible change. According to TGA (air atmosphere; heating 8"C/minute), the weight loss amounts to 1% at 3300C, to 5% at 363"C, to 10% at 373"C and to 20% to 384"C.

EXAMPLES 5 AND 6 Following the procedure of Example 2, a solution of 252g of N-(ss-hydroxyethyl)- tetrabromophthalimide in 420 ml of o-dichlorobenzene is produced with the reactants tetrabromophthalic acid anhydride (232 g. 0.5 mole) and ethanolamine (30.5 g, 0.5 mole).

20.75 g (U.125 mole) of isophthalic acid (Example 5) and 0.15 g of phosphoric acid are added to one half of the solution, whilst 58.0 g (0.125 mole) of tetrabromophthalic acid anhydride (Example 6) and 0.15 g of phosphoric acid are added to the other half, followed by esterification at an increasing temperature of 175 to 1900C in such a way that the water of reaction and 20 ml of o-dichlorobenzene are distilled off over a period of 5 hours.

The products are precipitated and worked up in the same way as before.

Isophthalic ester Tetrabromo-o-phthalic ester (Example 5) (Example 6) Amount weighed out: 140.6 g 175.4 g Yield: 98.6 % 95.9 % Melting Point: 238-247"C 280-284"C Elemental analysis: Obs. C 29.53 calc. C 29.37 obs. C 23.16 calc. C 23.01 H 1.37 H 1.04 H 0.79 H 0.54 N 2.48 N 2.44 N 1.99 N 1.92 Br 54.8 Br 55.9 Br 64.9 Br 65.7 Weight loss in air at 2000C after 3 h 0.78 % 3 h 1.7 % 24 h 1.40 % 24 h 3.5 % Thermogravimetry (air atmosphere; heating rate 8"C/minute) 1% 285"C 1 % 260"C 5 % 343 C 5 % 307 C 10 % 374 C 10 % 350 C 20 % 385 C 20 % 366 C EXAMPLES 7 AND 8 Following the procedure of Example 2, a solution of 500 g of N-(ss-hydroxyethyl)- tetrabromop'lthalimide in 800 ml of o-dichlorobenzene is produced with the reactants tetrabromophthalic acid anhydride (464 g, 1 mole) and ethanolamine (61 g, 1 mole). hour tenths of the solution, contaning 0.4 mole of N-(ss-hydroxyethyl)- tetrabromophthalimide, are diluted with 200 ml of o-dichlorobenzene, followed by the addition of 21.8 g (0.1 mole) of pyromellitic acid anhydride (Example 7) and 0.2 g of p-toluene sulphuric acid as esterification catalyst. Three tenths of the solution, containing 0.3 mole of N-(P-hydroxyethyl)-tetrabromophthalimide, are diluted with 100 ml of o-dichlorobenzene, followed by the addition of 19.2 g (0.1 mole) of trimellitic acid anhydride (Example 8) and 0.2 g of p-toluene sulphonic acid.

Both mixtures are esterified over a period of 4 hours at temperatures increasing from 155 to 1900C (bath temperature), the water of condensation and 35 ml of o-dichlorobenzene being distilled off during the esterification reaction.

The ester imide of pyromellitic acid (Example 7) form a substantially non-stirrable ester imide suspension which is diluted with 85 ml of o-dichlorobenzene.

Precipitation of the ester imides is completed by the addition of 200 ml of petroleum ether, the products are filtered off under suction, washed with petroleum ether and dried in vacuo at up to 2000C.

The ester imides of both Examples are in the form of substantially colourless powders.

Pyromellitic acid ester (Example 7) trimellitic acid (Example 8) ester Quantity weighed out: 201.2 g ester 159.8 g Yield: 90.8% 95.4 % Melting point: 311-317 C 197-212 C Elemental analysis: obs. C 27.26 calc. C 27.17 obs. C 28.03 calc. C 27.91 H 1.07 H 0.72 H 1.14 H 0.89 N 2.42 N 2.53 N 2.46 N 2.50 Br 57.1 Br 57.9 Br 56.8 Br 57.2 Weight loss in air at 2000C after 3 h 0.7 % 3 h 0.95 % 24 h 1.8 % 24 h 1.4 % Thermogravimetry (air atmosphere; heating rate 8"C/minute) 1 % 285 C 1 % 279 C 5 % 343 C 5 % 307 C 10 % 374 C 10 % 350 C 20 % 385 C 20 % 380 C EXAMPLE 9 A solution of 0.2 mole of N-(B-hydroxyethyl)-tetrabromophthalimide is prepared in the same way as in Example 2. Following the addition of 29.9 g (0.22 mole) of benzoic acid methyl ester and 0.17 g of the titanate of 2-ethyl-1,3-hexane diol, the mixture is transesterified at 155 to 1800C, the methanol formed being distilled off and small amounts of benzoic acid methyl ester being condensed and recycled. The evolution of methanol is over after 2 hours. 20 ml of o-dichlorobenzene are distilled off, the ester imide is precipitated with 150 ml of petroleum ether and worked up in the same way as before.

Yield. 116 g = 91.1 % of colourless ester imide (melting point 232-238 C) corresponding to the formula

Elemental analysis: observed C 33.13 calculated C 33.38 H 1.67 H 1.47 N 2.36 N 2.29 Br 52.1 Br 52.3 Weight loss at 200 C (air): 0.22 % after 3 h and 0.74 % after 24 h.

Thermogravimetry (air; heating rate 8 C/minute): 1 % at 286 C; 5 % at 307 C; 10 % at 3212 C; 20 % at 319 C.

EXAMPLES 10 TO 19 (Moulding compositions): Mixtures consisting of 86% by weight of PTMT (polytetramethylene terephthalate, strand granulate, reduced specific viscosity #sp/c = 1.54 d@/g (1% solution in a 60:40 mixture of phenol and o-dichlorobenzene at 25 C), 4% by weight of Sb2O3 and 10% by weight of each of the bromine-containing ester imides of Examples 1, 2, 3, 4, 5 and 9, are extruded in a twin screw extruder at 240 to 2

Two mixtures consisting of 56% by weight of PTMT, 30% by weight of short glass fibres (6 mm long), 4% by weight of Sb203 and 10% by weight of each of the ester imides of Examples 1 and 2 according to the invention are extruded twice in a single-screw extruder at 235 to 250"C and granulated (Examples 18 and 19).

No fuming or discoloration is observed during processing.

The following tests were carried out.

UL 94. The extruded strand is granulated and injection-moulded into test specimens measuring 127 x 12.7 x 1.6 mm for Underwriters Laboratories' Test UL 94.

LOI = Limiting Oxygen Index in % by volume of 2 indicates the limiting oxygen content of an O2/N2 mixture as a measure of further inflammability. The test specimens measure 52 x 140 x 1 mm. nSp/c The reduced specific viscosity of the PTMT component of the extruded strands is measured in order to determine any reduction in the molecular weight of the polyester attributable to the incorporation of the flameproofing agent which as far as possible should not exceed the reduction in molecular weight which always occurs as a result of processing.

M.p. ("C). The melting temperature of the PTMT component in the extruded strands was measured by differential thermo-analysis (DTA). A substantially unchanged or only slightly reduced melting temperature of the flameproofed PTMT is required in order to guarantee the possibility of post-condensation in the solid phase.

Weight loss. the weight loss was tested after storage in air at 150"C for 7, 14 and 28 days as a measure of the migration of the flameproofing agent in comparison with test specimens free from flameproofing agent.

Surface coating: The test specimens for the UL 94 test (14 days at 70"C) and the weight loss (after 28 days at 1500C) were tested for coatings or separation of the flameproofing agent.

TABLE 1 Example FP-agent FP-agent UL 94 LOI #SP/C m.p. C Weight loss % Surface No. of Example % by coating No. weight after 7 14 28 days at 150 C 1) 2) 5) 6) 7) 10 1 10 V0 32.0 1.36 216/227 0.15 0.17 0.22 8) 8) 11 2 10 V0 31.6 1.39 215/226 0.17 0.22 0.25 8) 8) 12 3 10 V0 32.7 1.24 213/222 0.12 0.19 0.23 8) 8) 13 4 10 V0 31.2 1.25 212/222 0.20 0.26 0.38 8) 8) 14 5 10 V0 32.2 1.26 214/225 0.21 0.26 0.43 8) 8) 15 9 10 V0 30.0 1.32 211/222 0.19 0.27 0.31 8) 8) 16 1 8.5 V0 32.7 1.38 - 0.11 0.14 0.19 8) 8) 17 2 8.5 V0 31.4 1.34 - 0.09 0.20 0.22 8) 8) 189) 1 10 V0 28.7 1.133) - 0.06 0.11 0.16 8) 8) 199) 2 10 V0 27.8 0.973) - 0.08 0.12 0.18 8) 8) Comparison - - 1.404) 214/226 0.06 0.08 0.14 - 1) FP-agent = flameproofing agent 2) The test was carried out immediately after production and after 14 days at 70 C; VO = best value 3) After extrusion without FP-agent with glass fibres, comparison value #sp/c = 1.25 4) After extrusion under identical conditions without the addition of FP-agent and without glass fibres 5) The first figure represents the temperature of the tangent intersection in the DTA diagram, the second figure is the maximum of the endothermic melting point 6) Surface testing after 14 days at 70 C 7) Surface testing after 28 days at 150 C 8) = unchanged surface 9) Containing 30% by weight of glass fibres * Measured as described in Example 10.

The following hlghly advantageous results were obtained: a) the reduction in viscosity during incorporation of the FP-agent is very low and far below the tolerance limit, despite the presence of ester groups in the FP-agent and the resulting possibilities of transesterification with PTMT, the reduction attributable to the FP-agent amounting to between 0.02 and at most 0.15 units. b) The melting temperatures of the flameproofed PTMT are in the range of the value for the unmodified PTMT, so that the possibility of post condensation in the solid phase remains intact. c) The flameproofing effect obtained with additions of only 10% by weight and even 8.5% by weight are excellent both in the freshly processed and also in the tempered state. d) None of the flameproofing agents according to the invention, although comparatively low molecular weight and uncrosslinked products, shows any tendency towards chalking out, even at service temperatures of 1500C. e) The flameproofing agents incorporated show no tendency towards decomposition or volatilization, even in the longterm test at 1500C.

EXAMPLE 20 A mixture consisting of 86% by weight of polyethylene terephthalate having a reduced specific viscosity of 1.36 dl/g, 10% by weight of the flameproofing agent of Example 1 according to the invention and 4% by weight of Sb203 is extruded in a twin screw extruder at 275 to 2900C.

Incorporation of the flameproofing agent does not present any difficulties. There is no discoloration nor any decomposition fumes and the reduced specific visosity of the polyethylene terephthalate component of the extruded strand falls only slightly to 1.27 dl/g.

The extruded strands are granulated and processed into test specimens in the same way as in Example 10.

Results: UL 94 VO/VO (immediately after production and after 14 days' storage of the test specimens at 70"C); no chalking out of the flameproofing agent and no surface coating after storage for 14 days at 700C or after storage for 28 days at 1500C; weight loss after 28 days in air at 1500C: 0.27%. The stored test specimen does not show any visible change.

EXAMPLES 21 TO 23 Three mixtures consistig of 94% by weight of polycarbonate based on bisphenol A (obtainable under the registered trade mark Makrolon) and 6% by weight of each of the flameproofing agents of Examples 1, 4 and 9 are extruded in a twin screw extruder at 245 to 255"C to form strands. Incorporation of the flameproofing agent does not present any problems. There is no sign of discoloration or decomposition.

The extruded transparent strands are granulated and moulded into 1 mm thick transparent panels which are then subjected to the tests described in Example 10.

Results: Example 21 Example 22 Example 23 (FP-agent (FP-agent (FP-agent of Example of Example of Example 1) 1) 4) 9) Mp/c r 0.50 0.51 0.50 UL 94 fresh V0 V0 V1 UL 94 after 14 days at 70"C V0 V0 V1 Oxygen index 29.6 30.4 28.8 Surface after 14 days at 700C unchanged unchanged unchanged Surface coating after 28 days at 1500C none none none 1) Reduced specific viscosity of the Makrolon component in the extruded compound; rasp, of the Makrolon used = 0.51 (1 % in chloroform at 25"C).

EXAMPLE 24 A mixture consisting of 93% by weight of an amorphous, transparent polyamide based on 2,2,4-trimethyl hexamethylene diamine and terephthalic acid (obtainable under the registered trade mark Trogamid T) and 7% by weight of bromine-containing ester imide of Example 1 is processed in a twin screw extruder at 250 to 265"C. Incorporation of the flameproofing agent does not present any difficulties. Transparent light-coloured strands with a tinge of orange are obtained. They are granulated and moulded into a 1 mm thick transparent panel.

Results: UL-94 fresh/after 14 days at 70"C V0/V0 Oxygen index 28.3 Surface after 14 days at 70"C no coating; no chalking out Surface coating after 28 days at 1500C none.

EXAMPLE 25 (acetalimide of glyoxal) In a reaction vessel equipped with a blade stirrer, dropping funnel and distillation bridge, 464 g (1 mole) of tetrabromophthalic acid anhydride are suspended in 1000 ml of o-dichlorobenzene. 61 g (1 mole) of ethanolamine, are added dropwise over a period of 30 minutes with vigorous stirring and cooling in an ice bath. The resulting suspension of the amidocarboxylic acid (III) is stirred for 30 minutes and subsequently heated for 1 hour to 175"C for cyclodehydration. Approximately 300 ml of a mixture of water of reaction and o-dichlorobenzene are distilled off over a period of 2.5 hours at a temperature in the range from 175 to 1900C.

After slight cooling to 110 - 1300C, 210 g of butanol, 56 g of toluene and 5 g of p-toluene sulphonic acid, together with 60 g of a 30% by weight aqueous glyoxal solution, are added to the resulting solution of N-(B-hydroxyethyl)-tetrabromophthalimide in odichlorobenzene. After a Vigreux column with a water separator has been attached, the solvent water and water of reaction are removed from the circuit at 120 to 155"C, which takes about 5 hours. When no more water distills over, the reaction mixture is heated and butanol and toluene are distilled off. After the column has been removed, the product is transacetalated at temperatures rising from 160 to 195 C. To begin with butanol, then a mixture of butanol and o-dichlorobenzene and, towards the end, o-dichlorobenzene, in all 300 ml of distillate, are distilled off over a period of 4 hours.

The acetalimide separates out in finely disperse form during the actual end phase of the reaction, resulting in the formation of an increasingly thickening, but still stirrable suspension. 400 ml of petrol (boiling range 80 to 100 C) are stirred in during cooling in order to complete precipitation and to produce a fine grain. The product is filtered off under suction at room temperature and washed once with petrol and once with methanol. It is then dried in vacuo at a temperature increasing to 180 C and then in air for 3 hours at 200 C.

481 g of a very light-coloured powder-form acetalimied are obtained.

Yield 94%.

Melting point: 328 to 3360C.

Elemental analysis: observed C 25.23 calculated C 24.68 H 0.87 H 0.88 N 2.60 N 2.74 Br 61.9 Br 62.6 Weight loss during storage under heat (in air at 2000C): 0.59% after 3 hours and 1.6% after 24 hours.

Thermogravimetry (air; heating rate 8 C/minute): 1 % at 295 C; 5 % at 354 C; 10 % at 368 C and 20 % at 379 C.

EXAMPLE 26 (acetalimide of glyoxal) In a reaction vessel of the type used in Example 25, 464 g of tetrabromophthalic acid anhydride are suspended in 1000 ml of o-dichlorobenzene and the suspension is heated to 110 C. At this temperature, 61 g of ethanolamine are run in within a few seconds, resulting in the formation of a solution of the amidocarboxylic acid (III). The temperature is then increased to 175 - 185 C over a period of 30 minutes for cyclodehydration, approximately 300 ml of a mixture of water and o-dichlorobenzene being distilled off within another 2.5 hours. On completion of cyclisation to form the N-( -hydroxyethyl)tetrabromophthalimide (II), the temperature is lowered to 130 C and 200 g of butanol, 60 g of a 30% aqueous glyoxal solution (18.1 g of glyoxal = 0.31 mole) and 5 g of p-toluene sulphonic acid as catalyst are added. After a Vigreux column has been attached, water and butanol are distilled off over a period of 4 hours at a bath temperature increasing to 1800C.

After the column has been removed, residues of butanol and some of the pdichlorobenzene are distilled off at a temperature increased to 1900C, so that the total quantity of the fractions distilled off amounts to around 500 ml.

The acetalimide is separated out and precipitated in the same way as in Example 25, after which it is filtered under suction. washed and dried in the same way as in Example.

487 g of a very light coloured. powder-form acetalimide are obtained.

Yield: 95%; melting point: 331 to 337 C.

Elemental analysis: observed C 25.31; H 0.85; N 2.63; Br 62.0 The IR-spectrum shows absorption bands of the imide function at 1765 cm-1 and 1705 cm-1 and absorption bands of the acetla function at 1330 cm-1 and 1385 cm-1. OH-Valency absorptions which could be indicative of (II) are not observed. Accordingly. the required acetalimide of structural formula (IV) is present.

Weight loss during storage under heat (in air at 200"C): 0.83C/c after 3 hours and 1.55% after 24 hours.

Thermogravimetry (air; heating rate 8 C/minute): 1% at 297 C; 5% at 352 C; 10% at 362 C and 20% at 375 C.

Differential thermoanalysis (heating rate 8 C/minute); strong endothermic peak at 318 C/336 C (beginning/maximum corresponding to the melting range of the acetalimide).

EXAMPLE 27 (acetalimide of terephthal dialdehyde) A solution of 500 g of N-( -hydroxyethyl)-tetrabromophthalimide in 750 ml of o-dichlorobenzene is prepared in accordance with Example 26. 33.5 g (0.25 mole) of terephthal dialdehyde. 150 g of butanol and 4 g of p-toluene sulphonic acid are added as catalyst.

After a Vigreux column has been attached, water and butanol are distilled off over a period of 3 hours at a temperature increased in stages to 175 C. After the column has been removed, residues of butanol and some of the o-dichlorobenzene (total quantity 450 ml) are distilled off at a temperature increased to 1900C. Precipitation is completed by the addition of 350 ml of petrol (80/100"C).

After filtration under suction, washing and drying as in Example 26, 507 g of a pale yellowish powder-form acetalimide are obtained.

Yield: 95%.

Melting point: 274 to 2860C.

Elemental analysis: observed C 28.06 calculated C 7.09 H 0.97 H 1.03 N 2.58 N 2.63 Br 59.1 Br 60.2 Weight loss during storage under heat (in air at 2000C): 1.3% after 3 hours and 3.4% after 24 hours.

EXAMPLES 28 to 33 Mixtures consisting of the quantities by weight indicated in Table 2, columns 2 to 4, of PTMT (polytetramethylene terephthalate, strand granulate, reduced specific viscosity = 1.60 dl/g), Sb203 and the acetalimide according to Example 1 are extruded in a twin screw extruder at 250 to 260"C to form a strand (Examples 28 to 31).

Corresponding mixtures of the above-mentioned PTMT, 30% by weight of short glass fibres (6 mm long), Sb2O2 and the acetalimide according to Example 26 are extruded twice in a single-screw extruder at a temperature in the range from 245 to 2600C (Examples 32 and 33).

Processing did not present any difficulties. Despite the high processing temperature, there is no evidence of any fuming or decomposition or discoloration.

The extruded strands are granulated and processed into test specimens measuring 127 x 12.7 x 1.6 mm for Underwriters Laboratories' Test UL 94.

The test specimens obtained in accordance with Examples 28 to 33 are subjected to the UL 94 fire test both immediately after production and also after storage for 14 days at 700C.

In addition, the surface of the test specimens was inspected for coating and, hence, for chalking out of the flameproofing agent. In addition, the surface of the test specimens was inspected for coating and, hence, for chalking out of the flameproofing agent. In addition, the test specimens were stored in air for 28 days at 1500C in order to assess their weight loss, surface discoloration or any other surface changes and any outward diffusion (chalking out) of the flameproofing agent.

The reduced specific viscosity of the pure PTMT before extrusion was measured at 1.6 that of the additive-free PTMT after extrusion at 1.41, that of Example 28 at 1.31 and that of Example 30 at 1.28 dl/g (1% in phenol/o-dichlorobenzene (60:40 at 250C).

The melting temperature of the PTMT component in the extruded strands was determined by differential thermo-analysis (tangent intersection). The minimum and maximum of the endothermic melting peak lay at 215/226"C and was completely unchanged in the test specimens according to Examples 28 and 31.

Storage under heat (150"C) for 28 days (long-term test) produces no coating, no chalking out of the flameproofing agent and no discoloration of the plastic.

The result of Examples 28 to 33 (Table 2) show a) that the reduction in the viscosity of the PTMT after incorporation of the flameproofing agent lies within the tolerance range; b) that the melting temperature of the PTMT is not lowered by the presence of a flameproofing agent so that the possibility of post-condensation in the solid phase remains intact; c) that the flameproofing effect is excellent (UL 94 rating V0) both in the freshly processed state and also in the tempered state, even when the quantity of flameproofing agent is reduced by 30% in relation to the standard quantity (10% of flameproofing agent, based on 100 parts by weight of compound); d) that the flameproofing agent according to the invention, although a comparatively low molecular weight, uncrosslinked product, shows no tendency to chalk out, even at service temperatures of 1500C; and e) that the flameproofing agent worked in shows no tendency towards decomposition, discoloration or volatilisation, even in the long-term test at 1500C.

TABLE 2 Example PTMT % Antimony tri- Acetalimide UL 94 UL 94 Oxygen Weight loss % ** No. by oxide % by % by weight fresh after index after 7 14 28 days weight weight 14 days fresh at 150 C at 70 C LOI 4 86 4 10 V0 V0 33.5 0.19 0.23 0.32 5 87.5 4 8.5 V0 V0 31.7 0.16 0.21 0.28 6 89 3.5 7.5 V0 V0 30.2 - - 7 89.5 3.5 7.0 V0 V0 29.6 0.11 0.18 0.23 8 56 * 4 10 V0 V0 31.4 0.12 0.16 0.20 9 57.5* 4 8.5 V0 V0 29.1 0.10 0.13 0.19 * + 30% by weight of glass fibres ** weight loss of PTMT without additives under identical temperature conditions 0.06% after 7 days; 0.08% after 14 days and 0.14% after 28 days.

EXAMPLE 34 A mixture consisting of 87.5% by weight of polyethylene terephthalate having a reduced specific viscosity of 1.36 dl/g, 8.5% by weight of the flameproofing agent according to Example 26 and 4% by weight of Sb203 is extruded in a twin screw extruder at 275 to 2900C.

Incorporation of the flameproofing agent does not present any difficulties. There is no sign of discoloration or decomposition and the reduced specific viscosity of the polyethylene terephthalate in the extruded strand falls to only 1.24 dl/g. The extruded strands are granulated, processed into test specimens for the UL 94 fire test and tested.

Results: UL 94: VO/VO (after production and after storage of the test specimens for 14 days at 70"C); no surface coating, no chalking out of the flameproofing agent and no discoloration of the test specimens after storage for 14 days at 700C or after storage for 28 days at 1500C.

The weight loss after tempering in air for 28 days at 1500C amounts to 0.31%.

EXAMPLE 35 A mixture consisting of 89% by weight of PTMT, 7.5% by weight of the acetalimide of Example 27 and 3.5% by weight of Sb203 is extruded in a twin screw extruder at 240 to 260"C, granulated, processed into test specimens in the same way as in Example 28 and tested.

Results: Problem-free incorporation of the flameproofing agent; no discoloration or decomposition.

UL 94 flame test. V0/V0.

Oxygen index. 30.1 Tempering (14 days) at 70"C and (28 days) at 1500C: no discoloration of the test specimens, no surface coating, no chalking out of the flameproofing agent.

Comparison Example A mixture consisting of 86% by weight of PTMT, 10 by weight of N-(P-hydroxyethyl)- tetrabromophthalimide and 4% by weight of Sb203 is extruded in a twin screw extruder under the conditions of Examples 28 to 31.

The compound flows out from the extruder nozzle in the form of a very thin liquid and, after solidification and cooling, the strands are so brittle that they immediately break when bent by hand.

The PTMT component in the extruded compound shows very serious molecular weight degradation. Its reduced viscosity has fallen from 1.60 dl/g to 0.92 dl/g.

After extrusion to form extremely brittle test panels, the UL 94 test produces a rating of V0. This value decreases considerably during thermal storage of the test specimens. During storage at 70"C, a thick coating forms on the surface of the test panels over a period of 14 days, indicating a pronounced tendency of the flameproofing agent to chalk out.

During storage at 1500C, a surface coating is formed after only a few days by chalking out of the flameproofing agent, through it undergoes partial sublimation and is deposited on the cooler parts of the drying cabinet as a crystalline product in the form of fine needles.

Weight loss of the compound under these conditions (150"C; air atmosphere): 0.28% after 7 days; 0.48% after 14 days and 1.04% after 28 days.

The tempered test specimen shows yellow-brown discoloration.

EXAMPLES 36 to 39 Mixtures of a) 92% by weight of polycarbonate based on bisphenol A b) 20% by weight of this polycarbonate together with 80% by weight of PTMT, c) 93% by weight of an amorphous transparent polyamide based on 2,2,4-trimethyl hexamethylene diamine and terephthalic acid (Trogamid T) d) 92% by weight of high pressure polyethylene were processed with 6% by weight of acetalimide according to Example 25 and 2% by weight of Sb203 in the case of a), b) and d) and with 7% by weight of the acetalimide in the case of c).

No difficulties were encountered during processing. The results of the UL 94 test were good and there was no sign of chalking out.

Claims (28)

1. WHAT WE CLAIM IS: 1. A tetrabromophthalimide derivative having the general formula:

   wherein R is a direct bond or a carboxyl-group-free radical derived from an aliphatic or aromatic, halogenated or halogen-free, mono, di, tri or tetra-carboxylic acid, and n is 1, 2, 3, or 4.
2. 2. A tetrabromophthalimide derivative having the general formula:

   wherein Rl is a direct bond or a phenylene group.
3. 3. A derivative as claimed in claim 1, wherein R is a radical derived from oxalic acid, furmaric acid, maleic acid, trimellitic acid, pyromellitic acid, ethane tricarboxylic acid, a brominated terephthalic acid, a brominated isophthalic acid, a brominated phthalic acid, a non-brominated terephthalic acid, a non-brominated isophthalic acid, or a non-brominated phthalic acid.
4. 4. A derivative as claimed in claim 2, wherein the radical ) CH-R-CH"" there of is a radical derived from glyoxal, terephthaldialdehyde, isophthalidialdehyde, or phthaldialdehyde.
5. 5. Process for producing a derivative as claimed in claim 1, which comprises esterifying or transesterifying N-(ss-hydroxyethyl)-tetrabromophthalimide with a carboxylic acid or derivative thereof at 150 to 220"C in a molar ratio of from 0.9 to 1.1 mole of N-(ss-hydroxyethyl)-tetrabromophathalimide per carboxyl group of the carboxylic acid or its derivative.
6. 6. Process as claimed in claim 5, wherein a derivative of a carboxylic acid is used, the derivative being an anhydride or ester thereof.
7. 7. Process for producing a derivative as claimed in Claim 2, which comprises reacting N-(ss-hydroxyethyl)-tetrabromophthalimide with a dialdehyde in a molar ratio of from 4:1 to 4:1.4.
8. 8. Process as claimed in claim 7, wherein the reaction is carried out in the presence of an alcohol.
9. 9. Process as claimed in any of claims 5 to 8, wherein the N-(ss-hydroxyethyl)- tetrabromophthalimide is produced by reacting tetrabromophthalic acid anhydride with aminoethanol to form the amidocarboxylic acid, and cyclising the amidocarboxylic acid thus formed at 100 to 2200C to form the desired N-(ss-hydroxyethyl)-tetrabromophthalimide.
10. 10. A tetrabromophthalimide derivative as claimed in claim 1, when produced by a process as claimed in claim 5 or 6, or by a process as claimed in claim 9 when appendant to claim 5 or 6.
11. 11. A tetrabromophthalimide derivative as claimed in claim 2, when produced by a process as claimed in claim 7 or 8, or by a process as claimed in claim 9 when appendant to claim 7 or 8.
12. 12. A tetrabromophthalimide derivative as claimed in claim 1, substantially as described in any of the foregoing Examples 1 to 9.
13. 13. A tetrabromophthalimide derivative as claimed in claim 2, substantially as described in any of the foregoing Examples 25 to 27.
14. 14. A moulding composition comprising a polymeric material and a tetrabromophthalimide derivative as claimed in any of claims 1, 3 and 10.
15. 15. A moulding composition comprising a polymeric material and tetrabromophthalimide derivative as claimed in any of claims 2, 4 and 11.
16. 16. A moulding composition as claimed in claim 14 to 15, wherein the polymeric material is an addition polymer.
17. 17. A moulding composition as claimed in claim 14 or 15, wherein the polymeric material is a polycondensate.
18. 18. A moulding composition as claimed in claim 17, wherein the polycondensate is a thermoplastic linear high molecular weight polyester.
19. 19. A moulding composition as claimed in claim 18, wherein the polyester is polyethylene terephthalate or polytetramethylene terephthalate.
20. 20. A moulding composition as claimed in claim 17, wherein the polycondensate is a polycarbonate, polyurethane or a polyamide.
21. 21. A moulding composition as claimed in claim 16, wherein the addition polymer is a vinyl homopolymer or copolymer.
22. 22. A moulding composition as claimed in claim 14 or 15, wherein the polymeric material is a hardenable resin.
23. 23. A moulding composition as claimed in any of claims 14 to 22, containing the tetrabromophthalimide derivative in an amount of from 3 to 20% by weight.
24. 24. A moulding composition as claimed in claim 23, containing the tetrabromophthalimide derivative in an amount of from 5 to 15% by weight.
25. 25. A moulding composition as claimed in any of claims 14 to 24, additionally including a synergistically acting substance.
26. 26. A moulding composition as claimed in claim 25, wherein said substance is antimony trioxide.
27. 27. A moulding composition substantially as described in any of Examples 10 to 24.
28. 28. A moulding composition substantially as described in any of Examples 28 to 39.