Flame-retardant thermoplastic polyurethane

Abstract

The present invention relates to compositions comprising at least one thermoplastic polyurethane, at least melamine cyanurate, at least one first phosphorus-containing flame retardant (F1) selected from the group consisting of alkyl esters of phosphoric acid and alkyl esters of phosphonic acid, where the alkyl radicals are selected from C1 to C12 alkyl radicals, and at least one further phosphorus-containing flame retardant (F2) selected from the group consisting of derivatives of phosphinic acid, and to the use of such a composition for production of cable sheaths.

Claims

1. A composition, comprising: a thermoplastic polyurethane in a range of from 30 to 75 wt. %, based on total composition weight; melamine cyanurate; a first phosphorus-containing flame retardant (F1) which is liquid at 21 C. and comprises an alkyl ester of phosphoric acid and an alkyl ester of phosphonic acid, alkyl radicals of the alkyl esters independently being C1 to C12 alkyl radicals, present in a range of from 2 to 15 wt. % based on the total composition weight; and a second phosphorus-containing flame retardant (F2) which is a derivative of phosphinic acid, present in a range of from 3 to 15 wt % based on the total composition weight.

2. The composition of claim 1, wherein the second flame retardant (F2) is a phosphinate.

3. The composition of claim 2, wherein the phosphinate comprises an aluminum phosphinate and/or a zinc phosphinate.

4. The composition of claim 1, wherein the first flame retardant (F1) is a trialkyl phosphate independently comprising C1 to C12 alkyl radicals.

5. The composition of claim 1, wherein the first flame retardant (F1) comprises a phosphonate of formula (I): ##STR00005## wherein A.sup.1 and A.sup.2 are each independently a linear or branched alkyl radical having 1 to 4 carbon atoms.

6. The composition of claim 1, wherein the melamine cyanurate has a particle size in a range of from 0.1 to 100 m.

7. The composition of claim 1, wherein the thermoplastic polyurethane comprises a thermoplastic polyurethane comprising, in polymerized form, (i) a diisocyanate and (ii-a) a polycarbonatediol or (ii-b) polytetrahydrofuran polyol.

8. The composition of claim 1, wherein the thermoplastic polyurethane has a mean molecular weight (M.sub.W) in a range of from 50,000 to 500,000 Da.

9. The composition of claim 1, wherein the thermoplastic polyurethane comprises, in polymerized form, diphenylmethane diisocyanate (MDI).

10. The composition of claim 1, wherein the thermoplastic polyurethane has a Shore hardness in a range of from 80 A to 100 A, determined in accordance with DIN 53505.

11. The composition of claim 1, wherein the thermoplastic polyurethane is present up to 60 wt. % of the total composition weight.

12. The composition of claim 1, wherein the melamine cyanurate is present in a range of from 20% to 40 wt. %, based on the total composition weight.

13. A cable sheath, comprising the composition of claim 1.

14. The composition of claim 1, wherein the first flame retardant (F1) comprises a trialkyl phosphate.

15. The composition of claim 1, wherein the melamine cyanurate is present in a range of from 25 to 40 wt. %, based on the total composition weight.

16. The composition of claim 1, wherein the melamine cyanurate is present in a range of from 30 to 40 wt. %, based on the total composition weight.

17. The composition of claim 1, comprising the flame retardant (F1) in an amount of from 3 to 10 wt. %, based on the total composition weight.

18. The composition of claim 11, comprising the flame retardant (F1) in an amount of from 5 to 8 wt. %, based on the total composition weight.

19. The composition of claim 1, wherein the thermoplastic polyurethane has a Shore hardness in a range of from 55 to 75 D, determined in accordance with DIN 53505.

20. The composition of claim 18, comprising the flame retardant (F2) in an amount of from 9 to 11 wt. %, based on the total composition weight.

Description

EXAMPLES

(1) The examples show the good mechanical properties have, good flame retardancy properties show, simultaneously good mechanical and chemical stability have, and are additionally discolored to a minor degree, if at all, when subjected to UV radiation.

(2) 1. Feedstocks

(3) Elastollan 1185A10: TPU of Shore hardness 85 A from BASF Polyurethanes GmbH, Elastogranstrasse 60, 49448 Lemforde, based on polytetrahydrofuran polyol (PTHF) having a molecular weight of 1000, butane-1,4-diol, MDI. Melapur MC 15 ED: Melamine cyanurate (1,3,5-triazine-2,4,6(1H,3H,5H)-trione, compound with 1,3,5-triazine-2,4,6-triamine (1:1)), CAS #: 37640-57-6, BASF SE, 67056 Ludwigshafen, GERMANY, particle size D99%<1=50 m, D50%<=4.5 m, water content % (w/w)<0.2. Fyrolflex RDP: Resorcinol bis(diphenylphosphate), CAS #: 125997-21-9, Supresta Netherlands B.V., Office Park De Hoef, Hoefseweg 1, 3821 AE Amersfoort, the Netherlands, viscosity at 25 C.=700 mPas, acid number<0.1 mg KOH/g, water content % (w/w)<0.1. Exolit OP 1230: Aluminum diethylphosphinate, CAS #: 225789-38-8, Clariant Produkte (Deutschland) GmbH, Chemiepark Knapsack, 50351 Hrth, water content % (w/w)<0.2, average particle size (D50) 20-40 m. Chisorb 622 LT: dimethyl butandioate, polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol, CAS #: 65447-77-0, BASF Polyurethanes GmbH, Postfach 1140, 49440 Lemfoerde, GERMANY. Tinuvin 234: 2-(2H-benzzotriazol-2-yl)4,6-bis(1-ethyl-1-phenylethylphenol), CAS #: 70321-86-17, BASF SE, 67056 Ludwigshafen, GERMANY. Disflamoll TOF: tris(2-ethylhexyl) phosphate, CAS #78-42-2, LANXESS Deutschland GmbH, 51369 Leverkusen.
2. Production of the Mixtures Table 1 below lists compositions in which the individual constituents are stated in parts by weight (PVV). The mixtures were each produced with a Berstorff ZE 40 A twin-screw extruder having a screw length of 35 D divided into 10 barrel sections.

(4) TABLE-US-00001 TABLE 1 Composition 1 (CE) 2 (CE) 3 1185A10 56.2 55 55 Disflamoll TOF 5 Fyroflex RDP 5 5 Melapur 15 ED 29.8 29.8 29.8 Exolit OP 1230 9 9 9 Tinuvin 234 0.6 0.6 Chisorb 622 LT 0.6 0.6 (CE) comparative example
3. Mechanical Properties The mixtures were extruded with an Arenz single-screw extruder having a three-zone screw with a mixing section (screw ratio 1:3) to give films having a thickness of 1.6 mm. Density, Shore hardness, tensile strength, tear propagation resistance, abrasion and elongation at break of the corresponding test specimens were measured. All compositions have good mechanical properties. The results are compiled in table 2.

(5) TABLE-US-00002 TABLE 2 Standard mechanical properties 1 (CE) 2 (CE) 3 Density [g/cm.sup.3] 1.287 1.347 1.27 Shore A 92 89 91 Tensile strength [MPa] 15 14 14 Elongation at break [%] 580 520 550 Tear propagation resistance [kN/m] 57 55 50 Wear [mm.sup.3] 90 131 97 (CE) comparative example

(6) Test Methods: Density: DIN EN ISO 1183-1, A Shore hardness A: DIN 53505

(7) Tensile strength: DIN EN ISO 527 Elongation at break: DIN EN ISO 527 Tear propagation resistance: DIN ISO 34-1, B (b Wear: DIN 53516
4. Discoloration on UV Exposure The mixtures were extruded with an Arenz single-screw extruder having a three-zone screw with a mixing section (screw ratio 1:3) to give films having a thickness of 1.6 mm. The delta E values (ASTM E313) of the corresponding specimens were measured after various exposure times by the method ASTM G155 Cy4. Lower delta E values were found for the TPU mixtures of the invention. The results are summarized in table 3.

(8) TABLE-US-00003 TABLE 3 Illumination according to ASTM G155 Cy4 Time 1 (CE) 2 (CE) 3 Color measurement in reflection 0 h (without specular reflection) Color separation delta E 0 0 0 Color measurement in reflection 0 h (with specular reflection) Color separation delta E 0 0 0 Color measurement in reflection 100 h (without specular reflection) Color separation delta E 4.8 1.9 1.1 Color measurement in reflection 100 h (with specular reflection) Color separation delta E 4.8 1.4 1.1 Color measurement in reflection 200 h (without specular reflection) Color separation delta E 9.3 4.5 2.1 Color measurement in reflection 200 h (with specular reflection) Color separation delta E 9.3 4.4 2.1 Color measurement in reflection 300 h (without specular reflection) Color separation delta E 14.9 8 3.1 Color measurement in reflection 300 h (with specular reflection) Color separation delta E 15 7.5 3.1 (CE) comparative example A small value for delta E represents lower discoloration caused by the test. The lower the discoloration in the test, the smaller the discoloration to be expected in practical use, for example under insolation.

(9) The results show that the materials of the invention have improved properties, especially good long-term stability.