FLAME-RETARDANT THERMOPLASTIC POLYURETHANE

Abstract

The present invention relates to compositions comprising at least one thermoplastic polyurethane, at least one polymer selected from the group consisting of ethylene-vinyl acetate copolymers, polyethylene, polypropylene, ethylene-propylene copolymers and copolymers based on styrene, at least one metal hydroxide and at least one phosphorus-containing flame retardant, wherein the thermoplastic polyurethane is selected from the group consisting of thermoplastic polyurethanes based on at least one diisocyanate and at least one polycarbonatediol and thermoplastic polyurethanes based on at least one diisocyanate and polytetrahydrofuran polyol. The present invention further relates to the use of such compositions for production of cable sheaths.

Claims

1.-20. (canceled)

21. A composition comprising at least one thermoplastic polyurethane, at least one polymer selected from the group consisting of ethylene-vinyl acetate copolymers, polyethylene, polypropylene, ethylene-propylene copolymers and copolymers based on styrene, at least one metal hydroxide and at least one phosphorus-containing flame retardant, wherein the thermoplastic polyurethane is a thermoplastic polyurethane based on at least one diisocyanate and at least one polycarbonatediol.

22. The composition according to claim 21, wherein the polymer is an ethylene-vinyl acetate copolymer.

23. The composition according to claim 21, wherein the thermoplastic polyurethane is a thermoplastic polyurethane based on at least one diisocyanate and at least one polycarbonatediol and the at least one polycarbonatediol is selected from the group consisting of polycarbonatediols based on butanediol and hexanediol, polycarbonatediols based on pentanediol and hexanediol, polycarbonatediols based on hexanediol, and mixtures of two or more of these polycarbonatediols.

24. The composition according to claim 21, wherein the polycarbonatediol has a number-average molecular weight Mn in the range from 500 to 4000, determined via GPC.

25. The composition according to claim 21, wherein the thermoplastic polyurethane has a mean molecular weight in the range from 50 000 to 150 000 Da.

26. The composition according to claim 21, wherein the thermoplastic polyurethane is based on diphenylmethane diisocyanate (MDI).

27. The composition according to claim 21, wherein the thermoplastic polyurethane has a Shore hardness in the range from 80 A to 95 A, determined in accordance with DIN 53505.

28. The composition according to claim 21, wherein the ethylene-vinyl acetate copolymer has a melt flow rate (190 C./2.16 kg) in the range from 4 to 8 g/10 min, determined in accordance with ASTM D1238.

29. The composition according to claim 21, wherein the metal hydroxide is selected from the group consisting of aluminum hydroxides, aluminum oxide hydroxides, magnesium hydroxide and a mixture of two or more of these hydroxides.

30. The composition according to claim 21, wherein the metal hydroxide is aluminum hydroxide.

31. The composition according to claim 21, wherein the metal hydroxide is at least partly enveloped by a shell.

32. The composition according to claim 21, wherein the phosphorus-containing flame retardant is selected from the group consisting of derivatives of phosphoric acid, derivatives of phosphonic acid, derivatives of phosphinic acid and a mixture of two or more of these derivatives.

33. The composition according to claim 21, wherein the phosphorus-containing flame retardant is selected from the group consisting of resorcinol bis(diphenyl phosphate) (RDP), bisphenol A bis(diphenyl phosphate) (BDP) and diphenyl cresyl phosphate (DPK).

34. The composition according to claim 21, wherein the proportion of the thermoplastic polyurethane in the composition is in the range from 15% to 65% based on the overall composition.

35. The composition according to claim 21, wherein the proportion of the polymer selected from the group consisting of ethylene-vinyl acetate copolymers, polyethylene, polypropylene, ethylene-propylene copolymers and copolymers based on styrene in the composition is in the range from 5% to 25% based on the overall composition.

36. The composition according to claim 21, wherein the proportion of the ethylene-vinyl acetate copolymer in the composition is in the range from 5% to 25% based on the overall composition.

37. The composition according to claim 21 wherein the proportion of the metal hydroxide in the composition is in the range from 45% to 65% based on the overall composition.

38. The composition according to claim 21, wherein the proportion of the phosphorus-containing flame retardant is in the range from 2% to 15% based on the overall composition.

39. A cable sheath comprising the composition according to claim 21.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0178] FIG. 1 shows the results of the cone calorimeter measurements of the mixtures in a Petrella plot. Plotted on the x axis here is the tendency of the material to contribute to a fast-growing fire (PHRR/t.sub.ig.sup.1/kWm.sup.2s.sup.1). Plotted on the y axis is the tendency of the material to contribute to a long-lasting fire (THE/MJm.sup.2). According to Petrella (Petrella R. V., The assessment of full scale fire hazards from cone calorimeter data, Journal of Fire Science, 12 (1994), p. 14), the quotient of maximum release of heat and ignition time is a measure of the extent to which the corresponding material will contribute to a fast-growing fire. Moreover, the total heat release is a measure of how the corresponding material will contribute to a long-lasting fire. Materials having better flame retardancies have very small x and y values. The materials V, VII, XIII and XIV (symbolized by the two filled circles) have better properties compared to comparative materials I, II and III (symbolized by the filled squares).