THERMOPLASTIC POLYURETHANE HAVING HIGH FLEXURAL STRESS

Abstract

The invention relates to a thermoplastic polyurethane obtainable by the reaction of at least the following formation components: one or more aliphatic diisocyanates A) having a molecular weight of 140 g/mol to 170 g/mol and one or more aliphatic diols B) having a molecular weight of 62 g/mol to 120 g/mol, wherein the formation components used to produce the thermoplastic polyurethane consist to an extent of at least 95% by weight of one or more aliphatic diisocyanates A) and one or more aliphatic diols B), based on the total mass of the formation components used, wherein the one or more aliphatic diisocyanates A) and the one or more aliphatic diols B) are used in a molar ratio in the range from 1.0:0.95 to 0.95:1.0, characterized in that the M.sub.z/M.sub.peak ratio of the thermoplastic polyurethane is within a range from 3 to 15, and to a process for preparation thereof, and to compositions, mouldings, films and/or fibres comprising the thermoplastic polyurethane.

Claims

1. A thermoplastic polyurethane polymer obtained by the reaction of at least the following formation components: A) one or more aliphatic diisocyanates having a molecular weight of 140 g/mol to 170 g/mol; and B) one or more aliphatic diols having a molecular weight of 62 g/mol to 120 g/mol, wherein the formation components used to produce the thermoplastic polyurethane polymer consist to an extent of at least 95% by weight of one or more aliphatic diisocyanates A) and one or more aliphatic diols B), based on a total mass of the formation components used, wherein the one or more aliphatic diisocyanates A) and the one or more aliphatic diols B) are used in a molar ratio in a range from 1.0:0.95 to 0.95:1.0, wherein the M.sub.z/M.sub.peak ratio of the thermoplastic polyurethane is within a range from 3 to 15, wherein M.sub.z is the centrifuge-average molar mass and M.sub.peak is the molar mass of the maximum of the gel permeation chromatography curve, each determined by gel permeation chromatography in hexafluoroisopropanol against polymethylmethacrylate as standard.

2. The thermoplastic polyurethane polymer according to claim 1, wherein the M.sub.z/M.sub.peak ratio of the thermoplastic polyurethane is within a range from 3 to 14.

3. The thermoplastic polyurethane polymer according to claim 1, wherein the M.sub.z of the thermoplastic polyurethane is within a range from 100 000 g/mol to 900 000 g/mol determined by gel permeation chromatography in hexafluoroisopropanol against polymethylmethacrylate as standard.

4. The thermoplastic polyurethane polymer according to claim 1, wherein the thermoplastic polyurethane polymer consists to an extent of at least 96% by weight of one or more aliphatic diisocyanates A) and one or more aliphatic diols B), based on a total mass of the polyurethane polymer.

5. The thermoplastic polyurethane polymer according to claim 1, wherein the one or more aliphatic diisocyanates A) are selected from the group consisting of 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 2-methyl-1,5-diisocyanatopentane and/or mixtures of at least two of these.

6. The thermoplastic polyurethane polymer according to claim 1, wherein the one or more aliphatic diols B) are selected from the group consisting of ethane-1,2-diol, propane-1,2-diol, propane-1,3-diol, butane-1,2-diol, butane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol and/or mixtures of at least two of these.

7. The thermoplastic polyurethane polymer according to claim 1, characterized in that the thermoplastic polyurethane polymer has a urethane group content of 40% by weight to 60% by weight based on a total weight of the thermoplastic polyurethane polymer.

8. The thermoplastic polyurethane polymer according to claim 1, wherein the thermoplastic polyurethane polymer has a percent by weight ratio of O to N determined by means of elemental analysis of ≥1.5:1 to 2.6:1 and a percent by weight ratio of N to C determined by means of elemental analysis of ≥1:10 to 1:3.

9. The thermoplastic polyurethane polymer according to claim 1, wherein the thermoplastic polyurethane polymer is a semicrystalline thermoplastic polyurethane polymer.

10. The thermoplastic polyurethane polymer according to claim 1, wherein the thermoplastic polyurethane has a glass transition point of <50° C., determined by differential scanning calorimetry according to DIN EN 61006 (November 2004).

11. The thermoplastic polyurethane polymer according to claim 1, wherein the thermoplastic polyurethane polymer has a melting point of >150° C., determined by differential scanning calorimetry according to DIN EN 61006 (November 2004).

12. The thermoplastic polyurethane polymer according to claim 1, wherein there is at least 100° C. between the glass transition point determined by differential scanning calorimetry according to DIN EN 61006 (November 2004) and the melting point determined by differential scanning calorimetry according to DIN EN 61006 (November 2004) of the thermoplastic polyurethane.

13. The thermoplastic polyurethane polymer according to claim 1, wherein the formation components used to produce the thermoplastic polyurethane polymer consist to an extent of 95% by weight to 99.9% by weight of one or more aliphatic diisocyanates A) and one or more aliphatic diols B) and to an extent of 0.1% by weight to 5% by weight of one or more polyisocyanates C) and/or one or more NCO-reactive compounds D), based on the total mass of the formation components used.

14. A process for preparing a thermoplastic polyurethane polymer according to claim 1, wherein, in a first step, at least one or more than one aliphatic diisocyanate A) having a molecular weight of 140 g/mol to 170 g/mol is reacted with one or more aliphatic diols B) having a molecular weight of 62 g/mol to 120 g/mol to give at least one prepolymer, and wherein the at least one prepolymer obtained in the first step is reacted in a second step with at least one chain extender to give the thermoplastic polyurethane polymer.

15. A composition, comprising at least one thermoplastic polyurethane polymer according to claim 1 and at least one additive and/or a further thermoplastic polymer.

16. A thermoplastic moulding compound, comprising at least one composition according to claim 15.

17. A moulding, film and/or fibre, comprising at least one thermoplastic polyurethane polymer according to claim 1, at least one thermoplastic moulding compound according to claim 16, or at least one composition according to claim 15.

18. Use of a thermoplastic polyurethane polymer according to claim 1, a thermoplastic moulding compound according to claim 16 or a composition according to claim 15 for production of a moulding, film and/or fibre.

19. Use of a thermoplastic polyurethane polymer according to claim 1 for production of a composition or a thermoplastic moulding compound.

Description

[0294] The figures and examples elucidated hereinafter serve to further elucidate the invention, but these merely constitute illustrative examples of particular embodiments, and not a restriction of the scope of the invention. The individual figures show:

[0295] FIG. 1: Preferred embodiment of a construction for performance of a two-stage continuous preparation of a thermoplastic polyurethane according to the invention, by reaction sequence in loop reactor and extruder.

EXAMPLES

[0296] All percentages are based on weight, unless stated otherwise.

[0297] The ambient temperature of 25° C. at the time of performing the experiments is referred to as RT (room temperature).

[0298] Raw Materials Used:

[0299] Hexamethylene 1,6-diisocyanate (HDI, purity≥99% by weight) was sourced from Covestro AG.

[0300] Butane-1,4-diol (BDO, purity≥99% by weight) was sourced from Ashland.

[0301] Hexafluoroisopropanol was sourced from flurochem in a purity of 99.9% by weight.

[0302] Potassium trifluoroacetate sourced from Aldrich, in a purity of 98% by weight.

[0303] Gel Permeation Chromatography:

[0304] The molar masses of the polymers were determined with the aid of gel permeation chromatography (GPC). For this purpose, the sample to be analysed was dissolved in a solution of 3 g of potassium trifluoroacetate in 400 cubic centimetres of hexafluoroisopropanol (sample concentration about 2 mg/cubic centimetre). The respective GPCs were measured with the following components at a flow rate of 1 cubic centimetre/minute:

TABLE-US-00002 Pump: 515 HPLC pump (Waters GmbH) Detector: Smartline 2300 RI detector (Knauer Wissenschaftliche Geräte Columns: 1 pre-column, 1000 Å PSS PFG 7 μm, 300 Å PSS PFG 7 μm, 100 Å PSS PFG 7 μm in the sequence specified Degassing: PSS degasser (Polymer Standards Service GmbH) Injection volume: 100 microlitres Temperature: 23° C.-25° C. Molar mass standard: Polymethylmethacrylate standard kit (PSS Polymer Standards Service GmbH)

[0305] Calculation of M.sub.z and M.sub.peak:

[0306] The centrifuge-average molar mass (M.sub.z) was calculated from the data obtained by the gel permeation chromatography measurement with the aid of the following equation:

[00003]${\stackrel{\_}{M}}_z=\frac{{.Math.}_i{n}_i{M}_i^3}{{.Math.}_i{n}_i{M}_i^2}\mathrm{in}g/\mathrm{mol}$

[0307] Abbreviations:

[0308] M.sub.i is the molar mass of the polymers of the fraction i, such that M.sub.i<M.sub.i+1 for all i, in g/mol,

[0309] n.sub.i is the molar amount of the polymer of the fraction i, in mol,

[0310] n is the total molar amount, n=Σ.sub.in.sub.i, in mol,

[0311] m.sub.i is the mass of the polymer of the fraction i, m.sub.i=n.sub.iM.sub.i, in g,

[0312] m.sub.g is the total mass of the polymer, m.sub.g=Σ.sub.im.sub.i, in g,

[00004]$w_i=\frac{m_i}{m_g}$

is the proportion by mass of the polymer in the fraction i.

[0313] As is known, molar mass distributions are typically plotted logarithmically against the molar mass, with the mass fractions to scale with the molar mass in order to assure area equality of the plot.

[0314] The peak molar mass, M.sub.peak, is found from the maximum of this logarithmic plot to be

[0315] M.sub.peak=M.sub.k, such that w.sub.k M.sub.k=max (w.sub.i M.sub.i) for all i, in g/mol.

[0316] Differential Scanning Calorimetry (DSC)

[0317] Melting points and glass transition points were determined by means of DSC (differential scanning calorimetry) with a Mettler DSC 12E (Mettler Toledo GmbH, Giessen, Germany) in accordance with DIN EN 61006 (November 2004). Calibration was effected via the melt onset temperature of indium and lead. 10 mg of substance were weighed out in standard capsules. The measurement was effected by three heating runs from −50° C. to +200° C. at a heating rate of 20 K/min with subsequent cooling at a cooling rate of 20 K/min. Cooling was effected by means of liquid nitrogen. The purge gas used was nitrogen. The values reported are each based on the evaluation of the 2nd heating curve.

[0318] Production of the Test Specimens:

[0319] The test specimens (80 mm×10 mm×4 mm bars) were produced by melting polymer pellets in a “Mikro Compounder Model 2005” from DSM Xplore. The processing temperature was set to 195° C. at 100 revolutions per minute. After a dwell time in the extruder of 2 minutes, the melt was transferred to the “Micro 10cc Injection Moulding Machine” from DSM Xplore. The injection mould was heated to 100° C. The injection moulding pressure was set to 6 bar (10 seconds). The hold pressure was 9 bar (10 seconds). The injection-moulded flexural specimens were manually demoulded after 20 seconds.

[0320] Determination of Maximum Flexural Stress:

[0321] Flexural stress was determined on the test specimens described above by means of a slow three-point bending test at room temperature to DIN EN ISO 178 (September 2013), conducted with an Instron 5566 universal tester at a speed of 5 mm/min, a fin radius of 5 mm and an application distance of 64 mm.

Preparation of Comparative Example 1

[0322] In a stirred tank (250 ml), 53.02 g of butane-1,4-diol was stirred with 96.92 g of HDI at 23° C. Subsequently, the reaction vessel was purged with nitrogen and heated to 90° C. while stirring (170 revolutions per minute, rpm). Once the internal temperature of the stirred tank had risen to 90° C., the heating was removed. Over the course of the next 5 minutes, the internal temperature rose to 240° C. The experiment was ended as the reaction mixture could no longer be stirred, since the product had solidified.

Preparation of Comparative Example 2

[0323] In a stirred tank (250 ml), 53.02 g of butane-1,4-diol was heated to 90° C. while stirring (170 rpm) with introduction of nitrogen for 30 minutes. Subsequently, 96.98 g of HDI was metered continuously into the butanediol over a period of 45 minutes. In the course of this, the temperature of the reaction mixture was increased constantly by 4° C. per minute until a temperature of 190° C. had been attained (25 minutes). As soon as a product temperature of 190° C. had been attained, the stirrer speed was increased to 300 rpm. The temperature in the stirred tank was kept constant between 190° C. and 200° C.

[0324] After the metered addition of HDI had ended, the melt was stirred for a further 5 minutes. Subsequently, it was poured into an aluminium mould in the hot state.

Preparation of the Inventive Examples 1-5 (FIG. 1)

[0325] From a 250 litre reservoir for hexamethylene 1,6-diisocyanate 1, with the aid of a toothed ring pump 2 (from HNP, MZR 7255), a hexamethylene 1,6-diisocyanate stream A was conveyed to a static mixer 7. The throughput of the hexamethylene 1,6-diisocyanate stream A was measured by means of a mass flow meter 3 (from Bronkhorst, Mini Con-Flow M1X, max. flow rate 12 kg/h). From a 250 litre reservoir for butane-1,4-diol 4, with the aid of a toothed ring pump 5 (from HNP, MZR 7205), a butane-1,4-diol stream B was conveyed to the static mixer 7. The throughput of the butane-1,4-diol stream was measured by means of a mass flow meter 6 (from Bronkhorst, Mini Con-Flow M1X, max. flow rate 8 kg/h). The temperature of the hexamethylene 1,6-diisocyanate was room temperature. The temperature of the butane-1,4-diol was 40° C. In the static mixer 7 (Sulzer SMX, diameter 6 mm, ratio of length to diameter L/D=10), the hexamethylene 1,6-diisocyanate stream A and the butane-1,4-diol stream B were mixed with one another. This is stream C.

[0326] The mixed and dispersed stream C is mixed in a circulation system with a circulating polymer stream D in a static mixer 8 (static mixer equivalent to Sulzer SMX, internal diameter 34 mm, L/D=20) to give a stream H. The temperature of stream D was 182° C.

[0327] The mixed and already partly reacted stream H was guided into a temperature-controllable static mixer 9. The reaction proceeded there for the most part, and the heat of reaction that arose was removed. The temperature-controllable static mixer 9 was of similar construction to a Sulzer SMR reactor with internal crossed tubes. It had an internal volume of 1.9 litres, and a heat exchange area of 0.44 square metre. It was heated/cooled with heat carrier oil. The heating medium temperature at the inlet was 180° C.

[0328] The product stream left the temperature-controllable static mixer 9 as a largely reacted stream E with a temperature of 183° C. At a branch 11, stream E was split into two substreams F and G. The pressure of substream F was increased at a gear pump 10. Substream F became the abovementioned substream D downstream of the pump.

[0329] The gear pump 10 (from Witte Chem 25,6-3) had a volume per cycle of 25.6 cubic centimetres and a speed of 50 per minute.

[0330] The whole circulation system was filled completely, and the polymer was largely incompressible. Therefore, the mass flow rate of stream G was identical to that of stream C. Stream G consisted of oligomer.

[0331] The whole circulation system consisted of jacketed pipelines and apparatuses that were heated with thermal oil. The heating medium temperature was 182° C.

[0332] Beyond the pressure-retaining valve 12, stream G was run past a three-way valve 13. On startup and shutdown or in the event of faults, it was possible to run said stream G to a waste vessel 14, an open 60 litre metal vat with air extraction. In regular operation, stream G was guided to an extruder 18.

[0333] From the hexamethylene 1,6-diisocyanate reservoir 1, with the aid of a micro toothed ring pump 15 (MZR 6355 from HNP), a hexamethylene 1,6-diisocyanate stream J was withdrawn. The throughput of the hexamethylene 1,6-diisocyanate stream J was measured by means of a mass flow meter 16 (from Bronkhorst, Mini Cori-Flow M1X, maximum flow rate 2 kg/h). The temperature of the hexamethylene 1,6-diisocyanate stream J was likewise room temperature. This stream was likewise guided to the extruder 18.

[0334] The extruder 18 was a ZSK 26 MC from Coperion, which was operated at temperatures of 200° C. and a speed of 66 revolutions per minute. In this extruder, stream G, by means of a venting system 17 that was operated at a reduced pressure of about 1 mbar relative to ambient pressure, was freed of any inert gases entrained with streams of matter A and B and of possible volatile reaction products. Downstream of the addition of the oligomer stream G, the hexamethylene 1,6-diisocyanate stream J was added and the reaction to give the polymer was conducted. Before the end of the extruder, the resulting polymer stream was freed of volatile constituents via a degassing operation 19. The pressure in this degassing was 200 mbar below ambient pressure. The polymer stream K was expressed through two nozzles, cooled in a water bath 20 filled with deionized water (DI water), and chopped into pellets by means of a pelletizer 21.

[0335] Description of the Extruder Configurations Used:

[0336] Where “elements” are mentioned in the description that follows, these may be one or more elements. It will be clear to the person skilled in the art that extruder elements, given the same outline, fulfil the same function, irrespective of subdivision.

[0337] Extruder Configuration for Inventive Examples 1-3:

[0338] A metering point with devolatilization, followed by reverse-conveying elements having a length of 12 mm, a conveying zone of 48 mm having elements of slope 48 mm, in which the HDI has been metered in, followed by a kneading zone of 144 mm, a conveying zone of 32 mm with elements of slope 16 mm, a zone of length 24 mm with conveying elements of slope 24 mm, a kneading zone of 24 mm, a conveying zone of 248 mm having elements of slope 16 and 24 mm, a zone having reverse-conveying elements of length 12 mm, a zone having conveying elements having a length of 132 mm with devolatilization, and a zone of length 120 mm with conveying elements of slope 24 mm as pressure buildup zone upstream of the nozzle.

[0339] Extruder Configuration for Inventive Example 4:

[0340] A metering point with devolatilization, followed by reverse-conveying elements having a length of 12 mm, a conveying zone of 48 mm having elements of slope 48 mm, in which the HDI has been metered in, followed by a kneading zone of 144 mm, a conveying zone of 12 mm with an element of slope 12 mm, a zone of length 24 mm with conveying elements of slope 24 mm, a kneading zone of 24 mm, a zone having conveying elements having a slope of 12 mm of length 228 mm, a zone of length 24 mm with conveying elements of slope 24 mm, a zone having reverse-conveying elements of length 12 mm, a zone having conveying elements having a length of 132 mm and slopes of 48 mm and 24 mm with devolatilization, and a zone of length 120 mm with conveying elements of slope 24 mm as pressure buildup zone upstream of the nozzle.

[0341] Extruder Configuration for Inventive Example 5:

[0342] A metering point with devolatilization, followed by a reverse-conveying element having a length of 12 mm, a conveying zone of 48 mm having elements of slope 48 mm, in which the HDI has been metered in, followed by a kneading zone of 96 mm, a conveying zone of length 312 mm with a slope of 12 mm, a zone of length 72 mm with conveying elements of slope 24 mm, a zone having reverse-conveying elements having a length of 12 mm of slope 12 mm, a conveying zone having a length of 120 mm and elements having slope 48 mm with devolatilization, and a zone having conveying elements of slope 24 mm having a length of 144 mm as pressure buildup zone upstream of the nozzle.

TABLE-US-00003 TABLE 1 Streams of matter that were used for preparation of the inventive examples. Inventive Inventive Inventive Inventive Inventive example 1 example 2 example 3 example 4 example 5 Stream A 2.91 5.97 5.97 2.91 2.91 [kg/h] Stream B 2.00 4.00 4.00 2.00 2.00 [kg/h] Stream J 0.78 1.34 1.27 0.78 0.78 [kg/h]

TABLE-US-00004 TABLE 2 Properties of the polymers described Comparative Comparative Inventive Inventive Inventive Inventive Inventive example 1 example 2 example 1 example 2 example 3 example 4 example 5 max. 70.9 70.6 79.1 76.2 73.9 74.1 73.1 flexural stress [MPa] M.sub.z 978 516 88 513 283 642 181 920 150 116 129 689 754 231 [g/mol] M.sub.peak  39 355 32 734  44 668  25 409  24 831  37 153  65 313 [g/mol] M.sub.z/M.sub.peak 24.9 2.7 6.4 7.2 6.1 3.5 11.6 Tg [° C.] 27 28 30 27 25 26 27 Tm [° C.] 181 185 188 185 184 186 182

[0343] Table 2 shows that the two products reported in the prior art have either a very large M.sub.z/M.sub.peak ratio (Comparative Example 1) or a small M.sub.z/M.sub.peak ratio (Comparative Example 2). The flexural stresses determined on these examples are about 71 MPa.

[0344] By contrast, the inventive examples have a quotient of M.sub.z/M.sub.peak within the range claimed of 3-15 and are notable for significantly higher flexural stresses of 73 MPa up to 79 MPa.