Flame-retardant thermoplastic polyurethane based on polycarbonate diols

Abstract

The present invention relates to compositions comprising at least one thermoplastic polyurethane, at least one metal hydroxide, and at least one phosphorus-containing flame retardant, where the thermoplastic polyurethane is a thermoplastic polyurethane based on at least one diisocyanate and on at least one polycarbonatediol. The present invention further relates to the use of compositions of this type for producing cable sheathing.

Claims

1. A composition comprising: from 30 to 90% of a thermoplastic polyurethane comprising copolymerized units of a diisocyanate and at least one polycarbonatediol; from 15 to 65% by weight of a metal hydroxide; and from 3 to 20% by weight of a phosphorus-containing flame retardant; wherein the phosphorus-containing flame retardant is a liquid at 21 C., the phosphorus-containing flame retardant is one selected from triesters of phosphoric acid of formula (I): ##STR00007## wherein R is optionally substituted alkyl, cycloalkyl, or phenyl groups, and n=from 1 to 15, the diisocyanate is diphenylmethane diisocyanate (MDI), 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, and polycarbonatediols based on hexanediol.

2. The composition according to claim 1, wherein the composition further comprises at least one of a phyllosilicate and a hydrotalcite.

3. The composition according to claim 2, wherein the composition comprises a phyllosilicate and the phyllosilicate is an organically intercalated phyllosilicate, the composition comprises a hydrotalcite and the hydrotalcite is an organically intercalated hydrotalcite, or the composition comprises a phyllosicate and a hydrotalcite which are organically intercalated.

4. The composition according to claim 2, comprising a phyllosilicate, wherein the phyllosilicate is bentonite.

5. The composition according to claim 2, wherein an amount of the at least one of a phyllosilicate and a hydrotalcite is from 0.5% by weight to 20% by weight, based on the total weight of the composition.

6. The composition according to claim 2, wherein a total weight % of the metal hydroxide, phosphorus-containing flame retardant, and the at least one of a phyllosilicate and a hydrotalcite is from 10 to 80%, based on the total weight of the composition.

7. The composition according to claim 1, wherein a number-average molecular weight Mn of the polycarbonatediol, determined by GPC, is from 500 to 4000.

8. The composition according to claim 1, wherein the metal hydroxide is at least one selected from the group consisting of aluminum hydroxides, aluminum oxide hydroxides, and magnesium hydroxide.

9. The composition according to claim 1, wherein the metal hydroxide is aluminum hydroxide.

10. The composition according to claim 1, wherein the metal hydroxide comprises an at least partial coating.

11. The composition according to claim 1, wherein the phosphorus-containing flame retardant is at least one selected from the group consisting of resorcinol bis(diphenyl phosphate) (RDP), oligomers of RDP, bis(diphenyl) 1,3-phenylenephosphate, bis(dixylenyl) 1,3-phenylenephosphate, and oligomeric products thereof with an average degree of oligomerization of n is from 3 to 6.

12. The composition according to claim 1, wherein a weight % of the metal hydroxide is from 20 to 50%, based on the total weight of the composition.

13. The composition according to claim 1, wherein a weight % of the phosphorus-containing flame retardant is from 5 to 20%, based on the total weight of the composition.

14. The composition according to claim 1, wherein a weight % of the metal hydroxide in the composition is from 20 to 50%, and a weight % of the phosphorus-containing flame retardant is from 5 to 20%, based on the total weight of the composition.

15. The composition according to claim 1, wherein the composition is suitable for producing cable sheathing.

Description

EXAMPLES

(1) The examples reveal the improved flame retardancy of the compositions of the invention, and also the good mechanical properties and hydrolysis resistance.

1. Production Example

(2) 1.1 Starting Material Elastollan 1185A10: TPU of Shore hardness 85A from BASF Polyurethanes GmbH, Elastogranstrasse 60, 49448 Lemforde, based on polytetrahydrofuran (PTHF) with molecular weight 1000, 1,4-butanediol, MDI. Elastollan A: TPU of Shore hardness 86A, experimental material, based on a polycarbonatediol from Bayer (Desmophen 2200), 1,4-butanediol, MDI. Elastollan B: TPU of Shore hardness 87A, experimental material, based on a polycarbonatediol from Ube (Eternacoll PH-200D), 1,4-butanediol, MDI. Martinal OL 104 LEO: aluminum hydroxide without coating, Martinswerk GmbH, Klner Strasse 110, 50127 Bergheim, Al(OH).sub.3 content [%]99.4, particle size (laser diffraction, Cilas) [m] D50: from 1.7 to 2.1; specific surface area (BET) [m.sup.2/g]: from 3 to 5. Magnifin H5 MV: magnesium hydroxide with a hydrophobic surface coating, Martinswerk GmbH, Klner Strasse 110, 50127 Bergheim, Mg(OH)2-content [%]>99.8, particle size (laser diffraction, Cilas) [m] D50: 1.6-2; specific surface area (BET) [m.sup.2/g]: 2-5 Nanofil 15: organically modified nano-dispersible phyllosilicate based on natural bentonites, Rockwood Clay Additives GmbH, Stadtwaldstrae 44, D-85368 Moosburg, powder, D50 average grain size, i.e. at least 50% of the particles are smaller than 40 m. Disflamoll TOF: Tris(2-ethylhexyl)phosphate, CAS 78-42-2, Lanxess Deutschland GmbH, 51369 Leverkusen Fyrolflex RDP: resorcinol bis(diphenyl phosphate), CAS #: 125997-21-9, Supresta Netherlands B. V., Office Park De Hoef, Hoefseweg 1, 3821 AE Amersfoort, The Netherlands.

(3) 1.2 Production by the Manual Casting Process

(4) The amount defined for the polyol and for the chain extenders in the parent formulation is weighed in the tin-plated steel container and briefly blanketed with nitrogen. The container is closed with a lid and heated to about 90 C. in an oven.

(5) Another oven is preheated to 80 C. for the heat-conditioning of the skin. The Teflon dish is placed on the hotplate, which is set to 125 C.

(6) The calculated amount of liquid isocyanate is determined volumetrically. For this, the liquid isocyanate is weighed in a PE beaker and poured out within 10 s into a PE beaker (the volumetric determination being carried out for MDI at a temperature of about 48 C.). The resultant emptied beaker is then tared and the calculated amount of isocyanate is charged thereto. In the case of MDI, this is stored at about 48 C. in an oven.

(7) Additions such as hydrolysis stabilizer, antioxidant, etc., where these are solid at RT, are weighed in directly.

(8) The preheated polyol is placed on an elevating platform under the stirrer, which is at rest. The reaction vessel is then raised by the elevating platform until the stirrer blades are completely immersed in the polyol.

(9) Before the stirrer motor is switched on, it is vital to ensure that the rotation rate controller is set at zero. The rotation rate is then slowly controlled upward in such a way as to ensure good mixing without incorporation of air.

(10) Additives, e.g. antioxidants, are then added to the polyol.

(11) The temperature of the reaction mixture is carefully adjusted to 80 C. by using a hot-air blower.

(12) If necessary, prior to the addition of isocyanate, catalyst is metered into the reaction mixture by using a microliter syringe. Isocyanate is then added at 80 C., by introducing the amount previously determined volumetrically within a period of 10 s into the reaction mixture. The weight is monitored by reweighing. Deviations of +/0.2 g from the amount in the formulation are recorded. The stop watch is started when the isocyanate is added. When the temperature reaches 110 C., the reaction mixture is poured out into the Teflon, dishes, which have been preheated to 125 C.

(13) 10 min after the stopwatch has been started, the skin is removed from the hotplate and then stored at 80 C. for 15 h in an oven. The cooled skin is comminuted in the chopper mill. The granules are then dried at 110 C. for 3 h, and stored under dry conditions.

(14) In principle, this method can also be used in a reactive extruder or in the belt process.

(15) Formulation for Elastollan A and B:

(16) TABLE-US-00001 Polycarbonatediol 1000 g Lupranat MET 460 g 1,4-Butanediol 115 g Elastostab H01 33 g Irganox 1125 33 g

(17) Polycarbonatediol used for producing Elastollan A comprises a polycarbonatediol from Bayer (Desmophen 2200), and polycarbonatediol used for producing Elastollan B comprises a polycarbonatediol from Ube (Eternacoll PH-200D).

2. ExampleFlame Retardancy

(18) In order to evaluate flame retardancy, a test specimen of thickness 5 mm is tested horizontally with a radiation intensity of 35 kW/m.sup.2 in a cone calorimeter in accordance with ISO 5660 part 1 and part 2 (2002-12).

(19) The tables below list compositions in which the proportions by weight (PW) are stated for the individual starting materials. Each of the mixtures was produced by using a ZE 40 A twin-screw extruder from Berstorff with screw length 35 D, divided into 10 barrel sections, and then extruded by using an Arenz single-screw extruder with a three-zone screw with mixing section (screw ratio 1:3) to give foils of thickness 1.6 mm. The test specimens for the cone measurements, measuring 2001505 mm, were injection-molded in an Arburg 520S with screw diameter 30 mm (zone 1zone 3: 180 C., zone 4zone 6: 185 C.). The sheets were then sawn to the size required for the cone measurement.

(20) TABLE-US-00002 TABLE 1 Parts by Experiment number weight 1 2 3 4 5 6 7 8 9 10 11 [PW] CE Ex Ex CE Ex CE Ex CE Ex CE Ex Elastollan 1185A10 [PW] 51 51 51 51 51 Elastollan A [PW] 51 Elastollan B [PW] 51 51 51 51 51 Fyrolflex RDP [PW] 10 10 10 10 10 11 11 11 11 Disflamoll TOF [PW] 10 10 Nanofil 15 [PW] 5 5 5 5 5 5 5 Martinal OL 104 LEO [PW] 34 34 34 34 34 38 38 Magnivin H5 MV [PW] 34 34 38 38 Ex: example according to the invention; CE: comparative example

(21) TABLE-US-00003 TABLE 2 Specifi- Experiment numbers Properties cation Unit 1 2 3 4 5 6 7 8 9 10 11 Time to ignition ISO [s] 70 79 78 80 73 64 57 91 83 53 61 (TIG, Time to 5660 Ignition) part 1 Total Heat [MJ/m.sup.2] 129 115 112 130 122 134 124 120 92 126 121 Release (THR) Peak of Heat [kW/m.sup.2] 150 159 161 291 257 193 159 497 324 267 199 Release Rate (PHRR) MAHRE [kW/m.sup.2] 116 107 104 207 211 138 121 259 217 173 139 residue [%] 26 29 28 31 30 27 30 20 26 33 31 Total smoke [m.sup.2/m.sup.2] 4296 2757 2965 n.d. n.d. 3039 2521 5335 4357 2608 2469 production on surface area basis Ratio of Peak of 2.1 2.0 2.1 3.6 3.5 3.0 2.8 5.5 3.9 5.0 3.3 Heat Release Rate to tTime to ignition (PHRR/TIG) n.d.: not determined

(22) 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 calculated from peak of heat release rate and time to ignition is a measure of the contribution that the material concerned makes to a rapidly growing fire. The total heat release is moreover a measure of the contribution that the material concerned makes to a fire of long duration.

(23) The results of the cone calorimeter measurements for mixtures 1 to 11 were depicted graphically in a Petrella plot, shown in FIGS. 1 to 5. The tendency of the material to contribute to a rapidly growing fire (PHRR/t.sub.ig.sup.1/kWm.sup.2 s.sup.1) has been plotted on the x-axis here. The tendency of the material to contribute to a fire of long duration (THR/MJm.sup.2) has been plotted on the y-axis. Materials with improved flame retardancy values here have minimized x and y values. The results have been collated in Table 2 and in the respective Petrella plot.

(24) The materials of the invention have higher flame retardancy. The mixtures of the invention exhibit lower smoke density.

3. ExampleMechanical Properties

(25) Mixture 1 is a comparative example, using a thermoplastic polyurethane based on polyether polyol.

(26) Mixtures 2 and 3 are mixtures of the invention, and show that the use of thermoplastic polyurethanes based on polycarbonatediols gives thermoplastic polyurethanes with good mechanical properties. Tensile strength, elongation at break (in accordance with DIN 53504) and Shore hardness A (in accordance with DIN 53505) were measured for the test specimens concerned.

(27) TABLE-US-00004 TABLE 3 Experiment number: Properties Specification Unit 1 2 3 Tensile strength DIN 53504 [MPa] 26 26 24 Elongation at break [%] 660 510 470 Shore hardness A DIN 53505 [MPa] 86 87 89

4. ExampleAging Resistance

(28) Mixture 1 is a comparative example, using a thermoplastic polyurethane based on polyether polyol. Mixtures 4 and 8 are also comparative examples.

(29) Mixtures 2 and 3 are mixtures of the invention, and show that the use of thermoplastic polyurethanes based on polycarbonatediols markedly improves flame retardancy. Also mixtures 5 and 9 are mixtures of the invention.

(30) In the context of this invention, the expression oxidative aging refers to an adverse change in mechanical parameters such as tensile strength, elongation at break, tear-propagation resistance, flexibility, impact strength, softness, etc. in the thermoplastic polyurethanes over the course of time.

(31) In order to evaluate oxidative aging resistance, a test specimen is aged at 113 C. for 7 days and at 121 C. for 7 days in a convection oven, and mechanical parameters are then determined. Tables 4, 5 and 6 below collate the results.

(32) TABLE-US-00005 TABLE 4 Specifi- Experiment numbers: Properties cation Unit 1 2 3 4 5 8 9 Tensile strength DIN 53504 [MPa] 26 26 24 29 28 29 30 Elongation at break [%] 660 510 470 570 450 680 450 After aging for 7 d/113 C. Tensile strength DIN 53504 [MPa] 16 24 21 25 25 27 28 Change in tensile [%] 38 8 13 14 11 17 7 strength Elongation at break DIN 53504 [%] 650 510 550 690 530 740 550 Change in elongation [%] 14 0 17 21 18 9 22 at break

(33) TABLE-US-00006 TABLE 5 Specifi- Experiment numbers: Properties cation Unit 1 2 3 4 5 8 9 Tensile strength DIN 53504 [MPa] 26 26 24 29 28 29 30 Elongation at break [%] 660 510 470 570 450 680 450 After aging for 7 d/121 C. Tensile strength DIN 53504 [MPa] 10 n.d. 16 21 22 20 26 Change in tensile [%] 62 n.d. 33 28 21 31 13 strength Elongation at break DIN 53504 [%] 430 n.d. 570 660 560 630 580 Change in elongation [%] 35 n.d. 21 +16 24 7 29 at break n.d.: not determined

(34) TABLE-US-00007 TABLE 6 Specifi- Experiment numbers: Properties cation Unit 1 2 3 4 5 8 9 Tensile strength DIN 53504 [MPa] 26 26 26 29 28 29 30 Elongation at break [%] 660 510 470 570 450 680 450 After aging for 7 d/136 C. Tensile strength DIN 53504 [MPa] 8 15 15 11 17 12 20 Change in tensile [%] 69 42 42 58 39 59 33 strength Elongation at break DIN 53504 [%] 190 440 440 520 580 470 580 Change in elongation [%] 71 19 6 12 29 31 29 at break

(35) Mixtures 2, 3, 5 and 9 are mixtures of the invention, and show that the use of mixtures comprising thermoplastic polyurethanes based on polycarbonatediols significantly reduces loss of strength due to heat treatment, i.e. markedly improves oxidative aging resistance.

5. ExamplesHydrolysis Resistance

(36) In order to evaluate the hydrolysis resistance, a test specimen is stored in water at 80 C. for 1008 hours, and mechanical parameters are then determined. Table 7 below collates the results.

(37) TABLE-US-00008 TABLE 7 Composition as in 0 h H.sub.2O/1008 h Residual % Experiment number 1 26 12 46 Experiment number 2 26 13 50

(38) Mixture 2 is a mixture of the invention, and shows that mixtures comprising thermoplastic polyurethanes based on polycarbonatediols have hydrolysis properties similar to those of mixtures comprising thermoplastic polyurethanes based on polyethers.

BRIEF DESCRIPTION OF THE FIGURES

(39) FIG. 1 shows the results of the cone calorimeter measurements for mixtures 1-3 in a Petrella plot. The tendency of the material to contribute to a rapidly growing fire (PHRR/t.sub.ig.sup.1/kWm.sup.2 s.sup.1) has been plotted on the x-axis here. The tendency of the material to contribute to a fire of long duration (THR/MJm.sup.2) has been plotted on the y-axis. 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 calculated from peak of heat release rate and time to ignition is a measure of the contribution that the material concerned makes to a rapidly growing fire. The total heat release is moreover a measure of the contribution that the material concerned makes to a fire of long duration. Materials with improved flame retardancy values have minimized x and y values. Materials 2 and 3 (symbolized by way of the solid squares) have better properties than comparative material 1 (symbolized by the solid triangle).

(40) FIG. 2 shows the results of the cone calorimeter measurements for mixtures 4 and 5 in a Petrella plot. The tendency of the material to contribute to a rapidly growing fire (PHRR/t.sub.ig.sup.1/kWm.sup.2 s.sup.1) has been plotted on the x-axis here. The tendency of the material to contribute to a fire of long duration (THR/MJm.sup.2) has been plotted on the y-axis. 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 calculated from peak of heat release rate and time to ignition is a measure of the contribution that the material concerned makes to a rapidly growing fire. The total heat release is moreover a measure of the contribution that the material concerned makes to a fire of long duration. Materials with improved flame retardancy values have minimized x and y values. Material 5 (symbolized by way of the solid square) have better properties than comparative material 4 (symbolized by the solid triangle).

(41) FIG. 3 shows the results of the cone calorimeter measurements for mixtures 6 and 7 in a Petrella plot. The tendency of the material to contribute to a rapidly growing fire (PHRR/t.sub.ig.sup.1/kWm.sup.2 s.sup.1) has been plotted on the x-axis here. The tendency of the material to contribute to a fire of long duration (THR/MJm.sup.2) has been plotted on the y-axis. 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 calculated from peak of heat release rate and time to ignition is a measure of the contribution that the material concerned makes to a rapidly growing fire. The total heat release is moreover a measure of the contribution that the material concerned makes to a fire of long duration. Materials with improved flame retardancy values have minimized x and y values. Material 7 (symbolized by way of the solid square) have better properties than comparative material 6 (symbolized by the solid triangle).

(42) FIG. 4 shows the results of the cone calorimeter measurements for mixtures 8 and 9 in a Petrella plot. The tendency of the material to contribute to a rapidly growing fire (PHRR/t.sub.ig.sup.1/kWm.sup.2 s.sup.1) has been plotted on the x-axis here. The tendency of the material to contribute to a fire of long duration (THR/MJm.sup.2) has been plotted on the y-axis. 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 calculated from peak of heat release rate and time to ignition is a measure of the contribution that the material concerned makes to a rapidly growing fire. The total heat release is moreover a measure of the contribution that the material concerned makes to a fire of long duration. Materials with improved flame retardancy values have minimized x and y values. Material 9 (symbolized by way of the solid square) have better properties than comparative material 8 (symbolized by the solid triangle).

(43) FIG. 5 shows the results of the cone calorimeter measurements for mixtures 10 and 11 in a Petrella plot. The tendency of the material to contribute to a rapidly growing fire (PHRR/t.sub.ig.sup.1/kWm.sup.2 s.sup.1) has been plotted on the x-axis here. The tendency of the material to contribute to a fire of long duration (THR/MJm.sup.2) has been plotted on the y-axis. 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 calculated from peak of heat release rate and time to ignition is a measure of the contribution that the material concerned makes to a rapidly growing fire. The total heat release is moreover a measure of the contribution that the material concerned makes to a fire of long duration. Materials with improved flame retardancy values have minimized x and y values. Material 11 (symbolized by way of the solid square) have better properties than comparative material 10 (symbolized by the solid triangle).