FLAME RETARDANT-STABILIZER COMBINATIONS FOR FLAME-RETARDANT POLYMERS HAVING IMPROVED HYDROLYSIS STABILITY AND USE THEREOF

Abstract

What are described are mixtures comprising selected phosphinic salts as component A, polymeric carbodiimide compounds as component B, and at least two of components C, D and/or G, where component C is a sterically hindered phenol, component D is an organic phosphite or phosphonite, and component G is a lubricant or demoulding agent. The mixtures may be used for production of flame-retardant compositions of thermoplastic polymers. These compositions feature enhanced hydrolysis stability.

Claims

1. Mixtures comprising: as component A 5% to 95% by weight of a phosphinic salt of the formula (Ia), a diphosphinic salt of the formula (Ib), or polymers or mixtures of two or more thereof, ##STR00007## in which R.sup.1, R.sup.2 are the same or different and are H or C.sub.1-C.sub.6-alkyl, linear or branched, and/or aryl, R.sup.3 is C.sub.1-C.sub.10-alkylene, linear or branched, C.sub.6-C.sub.10-arylene, -alkylarylene or -arylalkylene, M is H, Mg, Ca, Al, Sb, Sn, Ge, Ti, Fe, Zn, Zr, Ce, Bi, Sr, Mn, Li, Na, K and/or a protonated nitrogen base, m is 1 to 4, n is 1 to 4, and x is 1 to 4, as component B 0.5% to 20% by weight of a polymeric carbodiimide compound or mixtures thereof, as component C 0.5% to 20% by weight of a sterically hindered phenol or mixtures thereof, as component D 0% to 20% by weight of an organic phosphite and/or organic phosphonite or mixtures thereof, as component E 10% to 40% by weight of a condensation product of melamine; as component F 10% to 70% by weight of a filler or reinforcer or mixtures thereof, as component G 1% to 30% by weight of a lubricant and/or demoulding agent or mixtures thereof, and as component H 0% to 40% by weight of further additives other than components A to G, where the sum total of the weight components is 100% by weight.

2. Mixtures according to claim 1, wherein R.sup.1, R.sup.2 are identical or different and are methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl and/or phenyl.

3. Mixtures according to claim 1, wherein R.sup.3 is methylene, ethylene, n-propylene, isopropylene, n-butylene, tert-butylene, n-pentylene, n-octylene or n-dodecylene; phenylene or naphthylene; methylphenylene, ethylphenylene, tert-butylphenylene, methylnaphthylene, ethylnaphthylene or tert-butylnaphthylene; phenylmethylene, phenylethylene, phenylpropylene or phenylbutylene.

4. Mixtures according to claim 1, wherein polymeric —N═C═N-containing compounds of component B are compounds of the general formula (II) or (III) ##STR00008## where R.sup.4 is NCO, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, R.sup.10, R.sup.11 and R.sup.12 are independently hydrogen, or a radical from the group of C.sub.1- to C.sub.10-alkyl, C.sub.6- to C.sub.12-aryl, C.sub.7- to C.sub.13-aralkyl or C.sub.7- to C.sub.13-alkylaryl, g is an integer from 0 to 5, h is an integer from 2 to 100; ##STR00009## where, in formula (III), m is an integer from 2 to 5000, preferably an integer from 2 to 500, R.sup.3 is an arylene radical, preferably a 4,4′-methylenebis(2,6-dialkylphenyl) radical that bears, in at least one ortho position, preferably in both ortho positions, to the aromatic carbon atom that bears the —N═C═N— group, aliphatic and/or cycloaliphatic substituents having at least 2 carbon atoms, preferably branched or cycloaliphatic radicals having at least 3 carbon atoms, R′ is aryl, aralkyl, aryl-NCO or aralkyl-NCO and R″ is —N═C═N-aryl, —N═C═N-aralkyl or —NCO.

5. Mixtures according to claim 4, wherein component B comprises N═C═N-containing compounds of the formula (IV) or (V) ##STR00010## where R is ═NCO in which n is an integer from 2 to 200.

6. Mixtures according to claim 1, wherein component C is selected from the group consisting of alkylated monophenols, sterically hindered alkylthiomethylphenols, sterically hindered hydroxylated thiodiphenyl ethers, sterically hindered alkylidenebisphenols, sterically hindered benzylphenols, sterically hindered hydroxybenzylated malonates, sterically hindered hydroxybenzylaromatics, sterically hindered phenolic triazine compounds, sterically hindered phenolic benzyl phosphonates, alkyl N-(3,5-di-tert-butyl-4-hydroxyphenyl)carbamates, esters of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with mono- or polyhydric alcohols, esters of β-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionic acid with mono- or polyhydric alcohols, esters of β-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid with mono- or polyhydric alcohols, esters of 3,5-di-tert-butyl-4-hydroxyphenylacetic acid with mono- or polyhydric alcohols, amides of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and mixtures of two or more of these.

7. Mixtures according to claim 1, wherein component D is selected from the group consisting of organic phosphites of the general formula P(OR).sub.3 in which R are monovalent organic radicals, organic phosphonites of the general formula PR′(OR).sub.2 in which R and R′ are monovalent organic radicals.

8. (canceled)

9. Mixtures according to claim 1, wherein component F is selected from the group consisting of mineral particulate fillers based on talc, mica, silicate, quartz, titanium dioxide, wollastonite, kaolin, amorphous silicas, magnesium carbonate, chalk, feldspar and/or barium sulfate and/or glass fibres.

10. Mixtures according to claim 1, wherein component G is selected from the group consisting of long-chain fatty acids, salts thereof, ester derivatives and/or amide derivatives thereof, montan waxes and/or low molecular weight polyethylene and/or polypropylene waxes.

11. Compositions comprising, as well as the mixtures according to claim 1, further comprising as further components I, a thermoplastic polymer or a mixture thereof, preferably thermoplastic polyesters, thermoplastic polyamides, thermoplastic polyurethanes, thermoplastic-elastomeric polyesters, thermoplastic-elastomeric polyamides and/or thermoplastic-elastomeric polyurethanes.

12. Compositions according to claim 11, including 40% to 94.9% by weight of component I, 10% to 20% by weight of component A, 0.3% to 3% by weight of component B, 0% to 3% by weight of component C, 0% to 10% by weight of component D, 0% to 10% by weight of component E, 15% to 35% by weight of component F, 0% to 2% by weight of component G and 0% to 2% by weight of component H, where the sum total of the weight components is 100% by weight and where at least two of components C, D and/or G must be present.

13. Compositions according to claim 11, wherein component E is melem.

14. Compositions according to claim 11, wherein component F comprises mineral particulate fillers based on talc, mica, silicate, quartz, titanium dioxide, wollastonite, kaolin, amorphous silicas, magnesium carbonate, chalk, feldspar and/or barium sulfate and/or glass fibres.

15. Compositions according to claim 14, wherein component F comprises glass fibres.

16. Compositions according to claim 11, wherein component I comprises PBT or thermoplastic-elastomeric polyesters.

17. Compositions according to claim 11, wherein component G comprises long-chain fatty acids, salts thereof, ester derivatives and/or amide derivatives thereof, montan waxes and/or low molecular weight polyethylene and/or polypropylene waxes.

18. Process for producing hydrolysis-stable and flame-retardant polymer compounds, comprising mixing components A to I according to claim 11 by melt extrusion in the proportions by weight specified.

19. Fibres, films, mouldings and shaped articles made from hydrolysis-stable and flame-retardant polymer compounds according to claim 11.

20. Use of fibres, films and mouldings made from hydrolysis-stable and flame-retardant polymer compounds according to claim 11 in plugs, switches, capacitors, insulation systems, lamp sockets, coil forms, housings, controls and other articles.

21. Use of fibres, films, mouldings and shaped articles made from hydrolysis-stable and flame-retardant polymer compounds according to claim 11 in the domestic sector, in industry, in medicine, in motor vehicles, in aircraft, in ships, in spacecraft and in other means of locomotion, in office fitout, and in other articles and buildings.

Description

EXAMPLES

[0155] 1 Components Used

[0156] Thermoplastic polymers, component I:

[0157] polybutylene terephthalate (PBT): Ultradur® 4500 (BASF, D)

[0158] Thermoplastic copolyether ester elastomers (TPC):

[0159] Riteflex® 655 TPC unfilled (Celanese, Shore D hardness 55), referred to as TPC-55

[0160] Riteflex® 440 TPC unfilled (Celanese, Shore D hardness 40)

[0161] Nylon-6,6: Ultramid® A27, BASF

[0162] TPU: Elastollan® 1185, BASF

[0163] Component A:

[0164] aluminium salt of diethylphosphinic acid, referred to hereinafter as DEPAL.

[0165] Component B:

[0166] Stabaxol® P, polymeric carbodiimide, melting range 50-60° C., Lanxess

[0167] Stabaxol® P100, high molecular weight carbodiimide, melting range 75-85° C., Lanxess

[0168] Stabaxol® P110, high molecular weight carbodiimide, melting range 60-70° C.,

[0169] Lanxess

[0170] Stabaxol® PLF, polymeric carbodiimide without monomer components, Lanxess Lubio® AS 3, polymeric carbodiimide, Schafer Additivsysteme, referred to as AS 3 Lubio® AS 18, high molecular weight polymeric carbodiimide, Schäfer Additivsysteme, referred to as AS 18

[0171] Component C:

[0172] Irganox® 1010 (pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), from BASF, referred to as sterically hindered phenol

[0173] Irganox® 1330 (3,3′,3′,5,5′,5′-hexa-tert-butyl-a,a′,a′-(mesitylene-2,4,6-triyl)tri-p-cresol), from BASF, referred to as sterically hindered phenol

[0174] Irganox®245 ethylenebis(oxyethylene) bis(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate), referred to as sterically hindered phenol

[0175] Component E:

[0176] Melapur® MC 50 (melamine cyanurate), from BASF, referred to as MC

[0177] Melapur® 200/70 (melamine polyphosphate=MPP), BASF, referred to as MPP Delflam 20 (melem), Delamin, UK, referred to as melem

[0178] Component F:

[0179] PPG HP 3610 EC 10 4.5 mm glass fibres

[0180] PPG HP 3786 EC 10 4.5 mm glass fibres, from Nippon Electric Glass, NL Component G:

[0181] Lubricant: Licowax® E, montan wax, from Clariant, CH

[0182] Comparator

[0183] Araldite GT 7072; from Huntsman, CH, referred to as epoxide Lotader AX8900, from Arkema, impact modifier based on ethylene-methyl acrylate-glycidyl methacrylate terpolymer, referred to as AX 8900

[0184] 2. Production, Processing and Testing of Flame-Retardant Polyester, Polyamide and Polyurethane Compounds

[0185] The flame-retardant components were mixed with the polymer pellets and any additives in the ratio specified in the tables and incorporated in a twin-screw extruder (Leistritz ZSE 27/HP-44D) at temperatures of 240 to 280° C. The homogenized polymer strand was drawn off, cooled in a water bath, and then pelletized.

[0186] After sufficient drying, the moulding compounds were processed in an injection moulding machine (Arburg 320C/KT) at melt temperatures of 260 to 280° C. to give test specimens. The flame retardancy of the moulding compounds was tested by method UL94V (Underwriters Laboratories Inc. Standard of Safety, “Test for Flammability of Plastic Materials for Parts in Devices and Appliances”, page 14 to page 18, Northbrook 1998).

[0187] The fire tests were conducted by the UL 94 vertical test. The UL 94 fire classifications are as follows:

[0188] V-0: afterflame time never longer than 10 sec, total of afterflame times for 10 flame applications not more than 50 sec, no flaming drops, no complete consumption of the specimen, afterglow time for specimens never longer than 30 sec after end of flame application [0189] V-1: afterflame time never longer than 30 sec after end of flame application, total of afterflame times for 10 flame applications not more than 250 sec, afterglow time for specimens never longer than 60 sec after end of flame application, other criteria as for V-0 [0190] V-2: cotton indicator ignited by flaming drops, other criteria as for V-1 not classifiable (ncl): does not comply with fire classification V-2.

[0191] The examples report the afterflame time for 10 flame applications to 5 test specimens.

[0192] The determination of the hydrolysis stability was conducted with a CertoClav MultiControl 2 (laboratory autoclave) from CertoClav Sterilizer GmbH. The purpose of storing the sample in an autoclave was to test the degradation of the material as a result of high temperatures and high moisture content. The test specimens are preferably produced by injection moulding. The number of test specimens is guided by the tests required and the number of samplings envisaged, if any. Hydrolysis stability was tested in accordance with DIN EN 60749-33, i.e. heated storage under pressure in 100% relative humidity at 121° C. and 1 barg.

[0193] In addition, hydrolysis stability was also determined by storage of standard tensile specimens in a climate-controlled cabinet at 85° C. and 85% relative air humidity for 40 days. The crucial figures are the mechanical values before and after the hydrolysis test, and retention of the values after storage in percent.

[0194] Tensile properties were determined with a Z 010 tensile tester (from Zwick) according to DIN EN ISO 527-1/-2/-3. The method is used in order to examine the tensile deformation characteristics of test specimens and to ascertain the tensile strength, tensile modulus and other features of the tensile stress/strain relationship under fixed conditions. The test specimens are preferably produced by injection moulding. The number of test specimens is guided by the tests required. For the sample preparation, the test specimens are stored at 23° C./50% rel. humidity in a climate-controlled room for at least 16 h. Polyamide test specimens and other test specimens having high water absorption must be stored in a bag with an airtight seal at 23° C. and 50% rel. humidity for at least 24 h. The test specimen is stretched along its greatest principal axis at constant speed until it breaks or until the stress (force) or strain (change in length) reaches a defined value; during this operation, the stress borne by the test specimen and the change in length are measured. The measurement is effected in a climate-controlled room at 23° C. and 50% rel. humidity.

[0195] Examples of Polyester Elastomers

TABLE-US-00001 TABLE 1 Thermoplastic polyester elastomer: Stretching in freshly injection- moulded form and after a pressure cooker test (121° C., 1 barg) for 3 days; B1-2 are inventive examples V1 B1 B2 TPC-55 83.0 81.0 81.0 DepAl 12 12 12 MC 4.5 4.5 4.5 Stabaxol P 2 Stabaxol P100 2 Irganox ® 1010 0.3 0.3 0.3 Licowax E 0.2 0.2 0.2 UL94 0.8 mm V-2 V-2 V-2 AFT/s 14 32 26 Cotton bud burns/burning and 5/15 5/12 5/15 non-burning droplets Elongation (at break)/% T0* 352 343 306 T3* 16 252 228 Retention (break) after 3 days*/ 4 74 75 % Elongation (max)/% T0* 100 100 100 T3* 5 71 72 Modulus of elasticity (MPa) T0* 184 180 184 T3* 157 164 186 *0 = freshly injection-moulded, *3 = after storage in the PCT laboratory autoclave for 3 days (121° C., 1 barg)

[0196] Table 1 shows that flame-retardant thermoplastic elastomers can be obtained using DepAl, MC, polymeric carbodiimides, sterically hindered phenols and lubricants. The addition of carbodiimide, sterically hindered phenol and lubricants does not impair flame retardancy. After exposure in an autoclave for three days (pressure cooker test, 121° C., 1 barg), retention of up to 75% of the elongation at break is still found. No increase in pressure and no formation of gas or odour was observed on compounding.

PBT Examples

[0197]

TABLE-US-00002 TABLE 2 PBT GF 25 compounds: Stretching in freshly injection-moulded form and comparison after storage in a climate-controlled cabinet (85° C./85% rel. hum., 40 days) vs. pressure cooker test (PCT, 121° C., 1 barg, 3 days); B3 is an inventive example V2 V3 V4 B3 V5 V6 V7 V8 PBT 74.4 72.4 54.4 53.4 52.4 53.4 51.4 52.4 Glass fibres 25 25 25 25 25 25 25 25 DepAl 13.3 13.3 13.3 13.3 13.3 13.3 MC 6.7 6.7 6.7 6.7 6.7 6.7 Licowax E 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Lubio AS 3 1 Epoxide 2 2 1 3 AX 8900 2 Irganox ® 1010 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 UL94 0.8 mm burnt burnt V-0 V-0 V-1 V-1 V-1 V-1 AFT/s — — 47 22 96 83 119 87 Climate- Elongation (at break)/ T0* 3.1 3.08 2.35 2.27 1.61 1.95 1.16 2.36 controlled % T40* 1.67 2.40 0.79 1.99 0.71 0.79 0.59 0.87 cabinet (85° C./ Retention (break) after 54 78 34 88 44 41 51 37 85% rel. hum./ 40 days/% 40 days) Tensile strength (break)/ T0* 121 133 105 111 102 106 90 102 N/mm.sup.2 T40* 96 119 57 98 56 63 53 59 Modulus of elasticity T0* 8364 8925 9851 10029 10272 9976 10377 9377 (MPa) T40* 7882 8463 9140 9551 9637 9400 9699 8806 PCT (121° C./ Elongation (at break)/ T0* 3.1 3.08 2.4 2.27 1.61 1.95 1.16 2.36 100% rel. % T3* 1.3 2.3 0.7 1.43 0.67 0.56 0.4 0.58 hum./3 days) Retention (break) after 3 42 75 29 63 42 29 34 25 days/% Tensile strength (break)/ T0* 121 133 105 111 102 106 90 102 N/mm.sup.2 T3* 70 114 53 79 54 48 38 44 Modulus of elasticity T0* 8364 8925 9851 10029 10272 9976 10377 9377 (MPa) T3* 7609 8050 8724 8866 9368 9118 9301 8430 *0 = freshly injection-moulded, *3 = after storage in the PCT laboratory autoclave for 3 days (121° C., 1 barg), *40 = after 40 days in climate-controlled cabinet at 85° C. and 85% relative air humidity

[0198] Table 2 shows that flame-retardant and hydrolysis-stable PBT compounds can be produced using DepAl, MC, glass fibres, sterically hindered phenols, high molecular weight carbodiimide and lubricants. The UL94 fire classes are improved by the addition of polymeric carbodiimide. After storage in a climate-controlled cabinet at 85° C. and 85% relative air humidity for 40 days, elongation at break of 88% is still obtained with the flame-retardant polyester according to the invention. This elongation at break is very substantially comparable to the storage of the flame-retardant polyester for 2 to 3 days in an autoclave at 121° C. and 1 barg. The autoclave can thus be considered to be a rapid hydrolysis test with the PCT conditions. No increase in pressure and no formation of gas or odour was observed on compounding.

TABLE-US-00003 TABLE 3 PBT GF 25 V-0 compounds with and without hydrolysis stabilization. Tensile test before and after storage at 121° C. in an autoclave for 3 days; B4-7 are inventive examples; V4 was compounded once again for comparison V4 B4 B5 V9 B6 B7 PBT 54.4 53.4 53.4 53.7 53.4 53.4 Glass fibres 25 25 25 25 25 25 DepAl 13.3 13.3 13.3 13.3 13.3 13.3 MC 6.7 6.7 6.7 6.7 6.7 6.7 Licowax E 0.3 0.3 0.3 0.3 0.3 0.3 Stabaxol P Mw = 3000 1 Stabaxol P100 Mw = 15000 1 1 Stabaxol P110 Mw = 3000 1 Stabaxol PLF Mw = 4000 1 Irganox ® 1010 0.3 0.3 0.3 0 0.3 0.3 UL94 0.8 mm V-0 V-0 V-0 V-0 V-2 V-0 Elongation (at break)/% T0* 2.4 2.16 2.22 2.22 1.99 2.09 T3* 0.7 1.72 1.84 1.65 1.53 1.78 Retention (break) after 3 29 80 83 74 77 85 days*/% Tensile strength (break)/ T0* 105 105 108 108 107 104 N/mm.sup.2 T3* 53 85 86 79 82 84 Modulus of elasticity T0* 9851 10269 10332 10291 10064 10224 (MPa) T3* 8724 8987 8980 8876 8693 8938 *0 = freshly injection-moulded, *3 = after storage in the PCT laboratory autoclave for 3 days (121° C., 1 barg)

[0199] Table 3 shows that flame-retardant thermoplastic polyesters can be produced using DepAl, MC, glass fibres, sterically hindered phenols, carbodiimides having different molecular weights and lubricants, the highest retentions being achieved with the carbodiimides having molecular weights of >3000 g/mol. The UL94 fire classes are preserved or improved to a crucial degree through the addition of carbodiimide, sterically hindered phenol and lubricants. After storage in an autoclave at 121° C. and 1 barg for 3 days, elongations at break of nearly 80% were obtained in the case of flame-retardant polyesters that additionally contain carbodiimide. No increase in pressure and no formation of gas or odour was observed on compounding.

TABLE-US-00004 TABLE 4 PBT GF 25 V-0 compounds with and without hydrolysis stabilization. Tensile test in freshly injection-moulded form before and after storage at 121° C. in an autoclave for 3 days; B8 is an inventive example V4 V10 B8 PBT 54.4 54.4 53.4 Glass fibres 25 25 25 DepAl 13.3 13.3 13.3 MC 6.7 Melem 6.7 6.7 Licowax E 0.3 0.3 0.3 Lubio AS3 1 Irganox ® 1010 0.3 0.3 0.3 UL94 0.8 mm V-0 V-0 V-0 AFT/s 47 34 30 Elongation (at break)/% T0* 2.4 2.21 2.22 T3* 0.7 0.46 1.26 Retention (break) after 29 21 57 3 days*/% Tensile strength (break)/ T0* 105 104 110 N/mm.sup.2 T3* 53 39 78 Modulus of elasticity (MPa) T0* 9851 9597 9813 T3* 8724 8941 9273 *0 = freshly injection-moulded, *3 = after storage in the PCT laboratory autoclave for 3 days (121° C., 1 barg)

[0200] Table 4 shows that flame-retardant thermoplastic polyesters can be produced using DepAl, melem, glass fibres, sterically hindered phenols, high molecular weight carbodiimide and lubricants. The UL94 fire classes are preserved through the addition of carbodiimide, sterically hindered phenol and lubricants. After storage in an autoclave at 121° C. and 1 barg for 3 days, elongations at break of nearly 60% are still obtained in the case of flame-retardant polyesters that additionally include carbodiimide and sterically hindered phenols. No increase in pressure and no formation of gas or odour was observed on compounding.

[0201] Examples of Nylon-6

TABLE-US-00005 TABLE 5 PA6GF30: Stretching in freshly injection-moulded form and after a pressure cooker test (121° C., 1 barg) for 4 days. B9 is an inventive example. V11 V12 B9 PA 6 69.7 49.7 49.2 Glass fibres 30 30 30 Exolit OP 1400 (TP) 20 20 Lubio AS 18 0.5 Irganox ® 245 0.3 0.3 0.3 UL94 0.8 mm n.c. V-0 V-0 Elongation (at break)/% T0 4.7 3.4 3.4 T1* 8.4 6.7 7.4 T4* 7.3 4.8 5.7 Retention (break) after 4 days 87 71 77 in comparison to 1 day (saturation)*/% Tensile strength (break)/ T0 161 136 131 N/mm.sup.2 T4* 90 71 68 Modulus of elasticity (MPa) T0 9001 10843 10683 T4* 3952 5273 5000 *0 = freshly injection-moulded, *1 or 4 = after storage in the PCT laboratory autoclave for 1 or 4 days (121° C., 1 barg)

[0202] Table 5 shows that flame-retardant thermoplastic polyamides can be produced using Exolit OP 1400, glass fibres, sterically hindered phenols, polymeric carbodiimide and lubricants. The UL94 fire classes are very substantially preserved through the addition of polymeric carbodiimide, sterically hindered phenol and lubricants. After storage in an autoclave at 121° C. and 1 barg (PCT) for 4 days, elongation at break of 77% is still obtained. It should be noted here that the zero value of elongation on day 1 was taken after water storage, since saturation is established only after 24 hours. No increase in pressure and no formation of gas or odour was observed on compounding.

TPU Examples

[0203]

TABLE-US-00006 TABLE 6 TPU V-0 compounds with and without hydrolysis stabilization. Tensile strength before and after storage at 85° C. in water for 7 days. B10 and B11 are inventive examples. V13 V14 B10 V15 B11 TPU 99.7 84.5 83.5 69.5 69.0 DepAl 15 15 15 15 MC 15 15 Lubio AS 3 1 0.5 Irganox ® 1330 0.3 0.3 0.3 0.3 0.3 Licowax E 0.2 0.2 0.2 0.2 Tensile strength/N/mm.sup.2 44.0 21.3 21.7 11.4 12.4 TS after 7 d* 33.5 15.6 17.5 8.7 10.0 Retention/% 81 73 81 73 81 UL 94 1.6 mm burnt V-1 V-1 V-0 V-0 UL 94 1.6 mm after 7 d* burnt V-2 V-1 V-1 V-0 *after storage in water at 85° C. for 7 days

[0204] Table 6 shows that flame-retardant thermoplastic polyurethanes that still have more than 80% retention of tensile strength after storage in water at 85° C. for seven days can be obtained using DepAl, MC, sterically hindered phenols, high molecular weight carbodiimide and lubricants. No gas formation and no odour are observed on compounding, and the test specimens do not show any discolouration. The UL94 fire classes are preserved by the addition of the high molecular weight carbodiimides, the sterically hindered phenols and the lubricants, whereas a deterioration in fire class is observed without addition of carbodiimide.