PROCESS FOR CONTINUOUS PRODUCTION OF THERMOPLASTIC POLYURETHANE

Abstract

The present invention relates to a process for continuous production of thermoplastic polyurethane by reacting the components (A) one or more cycloaliphatic, aliphatic and/or araliphatic polyisocyanates and (B) one or more cycloaliphatic, aliphatic and/or araliphatic polyols, wherein the entirety of component (B) has a hydroxyl number of 600 mg KOH/g to 1830 mg KOH/g as determined according to DIN EN ISO 4629-2:2016. The process comprises the process steps of: a) preparing a mixture of a portion of component (A), a portion of or the entirety of component (B) and optionally a portion or the entirety of component (C), where in process step a) there is a molar ratio of component (A) to component (B) in the range from 0.6:1.0 to 0.95:1.0; b) mixing the mixture prepared in process step a) with an outgoing oligomerisate substream obtained from process step e); c) reacting the mixture from process step b); d) dividing the reaction mixture obtained in step c) into two outgoing substreams; e) recycling one outgoing substream from process step d) as an incoming substream for the mixture in process step b); f) mixing the remainder of component (A) and where present the remainder of components (B) and (C) with the remaining outgoing substream of process step d); and g) reacting the mixture obtained in process step f) to obtain a thermoplastic polyurethane. The invention further relates to thermoplastic polyurethane obtainable or obtained by the process of the invention, and also to a composition containing the thermoplastic polyurethane according to the invention and to the use thereof.

Claims

1. A process for continuous production of thermoplastic polyurethane by reaction of components (A) one or more cycloaliphatic, aliphatic and/or araliphatic polyisocyanates, (B) one or more cycloaliphatic, aliphatic and/or araliphatic polyols, wherein the total amount of component (B) has a hydroxyl number of 600 mg KOH/g to 1830 mg KOH/g, determined in accordance with DIN EN ISO 4629-2:2016, (C) optionally in the presence of one or more catalysts and/or one or more additives, wherein the process comprises the steps of: a) producing a mixture of a partial amount of component (A), a partial amount or the total amount of component (B) and optionally a partial amount or the total amount of component (C), wherein a molar ratio of component (A) to component (B) in process step a) is in the range from 0.6:1.0 to 0.95:1.0; b) mixing the mixture produced in process step a) with a prepolymer output substream obtained from process step e); c) reacting the mixture from process step b); d) dividing the reaction mixture obtained in step c) into two output substreams; e) recycling an output substream from process step d) as an input substream for the mixture in process step b); f) mixing the remainder of component (A) and optionally the remainder of components (B) and (C) with the remaining output substream of process step d); g) reacting to completion the mixture obtained in process step f) to obtain a thermoplastic polyurethane.

2. The process as claimed in claim 1, wherein the component (A) employed is one or more aliphatic and/or cycloaliphatic, monomeric diisocyanates having a molecular weight in the range from ≥140 g/mol to ≤400 g/mol.

3. The process as claimed in claim 1, wherein the component (A) employed is one or more monomeric diisocyanates selected from the group consisting of 1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1,4-diisocyanato-3,3,5-trimethylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, 1,3-diisocyanato-4-methylcyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; IPDI) and/or mixtures of at least 2 of these.

4. The process as claimed in claim 1, wherein the component (B) employed is one or more cycloaliphatic, aliphatic and/or araliphatic polyols having a hydroxyl number of 600 mg KOH/g to 1830 mg KOH/g, determined in accordance with DIN EN ISO 4629-2:2016.

5. The process as claimed in claim 1, wherein the component (B) employed is one or more diols 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, heptane-1,7-diol, octane-1,8-diol, nonane-1,9-diol, cyclobutane-1,3-diol, cyclopentane-1,3-diol, cyclohexane-1,2-diol, -1,3-diol and -1,4-diol, cyclohexane-1,4-dimethanol, diethylene glycol and/or mixtures of at least 2 of these.

6. The process as claimed claim 1, wherein process step a) employs the total amount of component (B).

7. The process as claimed in claim 1, wherein the components (A) and (B) are altogether employed in a molar ratio in the range from 0.9:1.0 to 1.2:1.0 over all process steps.

8. The process as claimed in claim 1, wherein the temperature in process step a) is not less than 25° C. and not more than 60° C.

9. The process as claimed in claim 1, wherein the temperature in process step c) is not less than 170° C. and not more than 190° C.

10. The process as claimed in claim 1, wherein at least process step g) is performed in an extruder and optionally wherein the temperatures in process step g) are not less than 180° C. and not more than 260° C.

11. (canceled)

12. The process as claimed in claim 1, wherein the molar ratio of the partial amounts of component (A) employed in process step a) and in process step f), calculated as moles of component (A) in a)/[moles of component (A) in f) plus moles of component (A) in a)], is not less than 0.9 and not more than 0.65.

13. The process as claimed in claim 1, wherein the weight ratio of the prepolymer recycled in process step b) based on the amount of mixture of component (A) and component (B) employed is not less than 10 and not more than 30.

14. The process as claimed in claim 1, wherein the partial amount of component (A) and optionally partial amount of component (B) and/or partial amount of component (C) added in process step f) has a temperature of not less than 10° C. and not more than 150° C.

15. The process as claimed in claim 1, wherein the prepolymers of the output stream from step e) consist essentially of hydroxy-terminated prepolymers.

16. The process as claimed in claim 1, wherein at least process steps b), c), d) and e) are performed in a loop reactor.

17. The process as claimed in claim 16, wherein the loop reactor has a pressure control means and the pressure is set in the range from 2 bar absolute to 11 bar absolute and/or wherein the viscosity of the material stream in the loop reactor is below 10 Pa.Math.s at a measurement temperature of 190° C. and a frequency of 10 Hz, determined in accordance with ISO 6721-10:2015.

18. (canceled)

19. The process as claimed in claim 16, wherein the loop reactor has at least one heat exchanger having a heat-transfer capacity, based on the total volume of the loop reactor, of more than 10 kW/(m.sup.3.Math.K).

20. The process as claimed in claim 19, wherein the loop reactor has at least one heat exchanger and the ratio of heat-transfer surface area to loop reactor surface area is >0.3 and/or wherein the heat-transfer surface area in the reactor has an average k value of >50 W/(m.sup.2.Math.K).

21. (canceled)

22. The process as claimed in claim 1, wherein the thermoplastic polyurethane is essentially formed by polyaddition of combinations of component (A) and component (B) selected from the group consisting of 1,4-diisocyanatobutane with ethane-1,2-diol, 1,4-diisocyanatobutane with propane-1,2-diol and/or -1,3-diol, 1,4-diisocyanatobutane with butane-1,2-diol, -1,3-diol and/or -1,4-diol, 1,4-diisocyanatobutane with pentane-1,5-diol, 1,4-diisocyanatobutane with hexane-1,6-diol, 1,5-diisocyanatopentane with ethane-1,2-diol, 1,5-diisocyanatopentane with propane-1,2-diol and/or -1,3-diol, 1,5-diisocyanatopentane with butane-1,2-diol, -1,3-diol and/or -1,4-diol, 1,5-diisocyanatopentane with pentane-1,5-diol, 1,5-diisocyanatopentane with hexane-1,6-diol, 1,6-diisocyanatohexane with ethane-1,2-diol, 1,6-diisocyanatohexane with propane-1,2-diol and/or -1,3-diol, 1,6-diisocyanatohexane with butane-1,2-diol, -1,3-diol and/or -1,4-diol, 1,6-diisocyanatohexane with pentane-1,5-diol and 1,6-diisocyanatohexane with hexane-1,6-diol.

23. A thermoplastic polyurethane obtained by the process as claimed in claim 1.

Description

[0100] Further advantages and advantageous configurations of the objects according to the invention are illustrated by the drawings and elucidated in the description that follows. It should be noted that the drawings are merely of a descriptive nature and are not intended to limit the invention. In the figures:

[0101] FIG. 1 shows a possible setup for continuous production of the polyurethanes according to the invention; and

[0102] FIG. 2 shows a diagram for definition of the process and the process steps and the material streams of the process according to the invention.

[0103] FIG. 1 shows a possible setup for continuous production of hydroxy-terminated prepolymers. The HDI stream (stream A) is withdrawn from the HDI tank 1 by means of a pump 2. The amount withdrawn may be measured via a mass flow meter 3 and optionally controlled by feedback to the pump 2. A similar setup arises for the BDO tank 4 with BDO pump 5 and flow meter 6 (stream B). The two streams A and B are conveyed into the static mixer 7 and mixed with one another to form stream C. Stream C is mixed with a recirculating oligomer stream D in the temperature-controllable mixers 8, 9 to form stream E, with stream E undergoing reaction in the mixers 8, 9 and in the pipe conduits. Stream E is split at the branching point 11 into two substreams (streams F and G). Downstream of the pressure-retaining valve 12, stream G is run past a three-way valve 13. It may be advantageous to run material generated during startup and shutdown of the plant or during malfunctions to a waste container 14. In regular operation, stream G is passed to an extruder 18. An HDI stream J is withdrawn from the container 1 and via a pump 15 and a mass flow meter 16, with which the HDI stream J is measured and optionally controlled, supplied to the extruder 18 in which it is mixed with stream G and the mixture is reacted. The extruder 18 may have apparatuses, 17, 19 for degassing the molten polymer at the inlet and outlet. The extruded polymer stream K may be expressed through nozzles, cooled in a water bath 20 filled with DM water and chopped into pellets by means of a pelletizer 21.

[0104] FIG. 2 shows a schematic representation of the sequence of events and the material streams of the process according to the invention. Stream A and B are the reactant streams of components (A) and (B), a portion of the altogether employed amount of component (A) being added via stream A. Component (B) is supplied to the process only via stream B. Streams A and B are mixed (1) (stream C), stream C is then mixed with stream D, stream D being formed by recycling of stream F. The mixture of streams C and D is stream E. Said stream is divided, one of the substreams (stream F) being recycled, i.e. recirculated. The other substream (stream G) is mixed with the other substream of component (A) (stream J) and the mixture is reacted, extruded, cooled and chopped.

EXAMPLES

[0105] All percentages are based on weight unless otherwise stated.

[0106] The ambient temperature of 25° C. at the time of performing the experiment is referred to as RT (room temperature).

I. Raw Materials Used

[0107] Hexamethylene 1,6-diisocyanate (HDI, purity ≥99% by weight) was obtained from Covestro Deutschland AG.

[0108] Butane-1,4-diol (BDO, purity ≥99% by weight) was obtained from Ashland Industries Deutschland GmbH.

Example 1

[0109] An annular gear pump 2 (HNP, MZR 7255) was used to convey an HDI stream A from a 250 liter tank for HDI 1 to a static mixer 7. The throughput of the HDI stream A was measured using a mass flow meter 3 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 12 kg/h) and adjusted to a value of 2.911 kg/h. An annular gear pump 5 (HNP, MZR 7205) was used to convey a BDO stream B from a 250 liter tank for BDO 4 to the static mixer 7. The throughput of the BDO stream was measured using a mass flow meter 6 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 8 kg/h) and adjusted to a value of 2.000 kg/h. The temperature of the HDI was ambient temperature, about 25° C. The temperature of the BDO was 40° C. In the static mixer 7 (Sulzer SMX, diameter 6 mm, length-to-diameter ratio L/D=10) the HDI stream A and the BDO stream B were mixed with one another. This is stream C.

[0110] The mixed and dispersed stream C is in a circuit mixed with a circulating polymer stream D in an externally temperature-controlled static mixer 8 (static mixer equivalent to Sulzer SMX, internal diameter 34 mm, L/D=20) to afford a stream H. Heat was also already transferred into this static mixer and the heat transfer surface area was 0.05 square meters. The temperature of stream D was 182° C.

[0111] The mixed and already partly reacted stream H was passed into a temperature-controllable static mixer 9. The reaction was largely completed therein and the resulting heat of reaction is 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 2.2 liters and a heat exchange surface area of 0.31 square meters. Under the operating conditions, its heat-exchange capacity based on the product side was 78 watts per kelvin. Based on the total volume of the loop reactor of 4 liters, the heat-transfer coefficient was 19 kilowatts per cubic meter per kelvin. It was heated/cooled with heat-transfer oil. The heating medium temperature at the inlet was 180° C.

[0112] The ratio of the heat transfer surface area to the total surface area was thus (0.31+0.05)/(0.31+0.05+0.18)=0.655.

[0113] The heat-transfer coefficient in the temperature-controllable static mixer was 270 watts per square meter per kelvin.

[0114] The product stream exited the temperature-controllable static mixer 9 as a largely fully-reacted stream E at a temperature of 183° C. At a branching 11, stream E was divided into two substreams F and G. The pressure of substream F was increased in a gear pump 10. Substream F became the abovementioned substream D downstream of the pump.

[0115] The gear pump 10 (Witte Chem 25,6-3) had a volume per revolution of 25.6 cubic centimeters and a speed of 50 revolutions per minute. The pumped stream G thus amounted to 75 kg/h.

[0116] The whole circuit was full and the polymer was largely incompressible. The mass flow rate of stream G was therefore identical to that of stream C. Stream G consisted of oligomer.

[0117] The whole circuit consisted of double-walled pipe conduits and apparatuses heated with thermal oil. The heating medium temperature was 182° C.

[0118] The mass flow G was then passed through a pressure control valve 12. The pressure in the pressure control valve 12 was over the course of the test controlled in such a way that a pressure in the circuit was between 4 and 7 bar abs. This resulted in a single-phase flow in the entire circuit without exceeding the pressure resistance of all apparatuses.

[0119] Downstream of the pressure control 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 liter metal vat with extraction. In regular operation, stream G was passed to an extruder 18. The stream at the waste container 14 was sampled under steady-state conditions and the viscosity was 0.81 Pa.Math.s at 190° C. and a frequency of 10 Hz.

[0120] A micro annular gear pump 15 (MZR 6355 from HNP) was used to withdraw an HDI stream J from the HDI tank 1. The throughput of the HDI stream J was measured using a mass flow meter 16 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 2 kg/h) and adjusted to 0.784 kilograms per hour. The temperature of the HDI stream J was also room temperature, about 25° C. This stream was also passed to the extruder 18. The extruder 18 was a ZSK 26 MC from Coperion which was operated at a speed of 66 revolutions per minute. In this extruder, stream G was freed of any inert gases entrained with material streams A and B and of possible volatile reaction products by means of a venting system 17 operated at a negative pressure of about 1 mbar relative to ambient pressure. Downstream of the addition of the oligomer stream G, the HDI stream J was added and the reaction to afford the polymer was performed. The resulting polymer stream was also freed of volatile constituents via a degassing 19 before the end of the extruder. The pressure in this degassing was 200 mbar below ambient pressure. The barrel temperatures of the extruder were set to between 190° C. and 210° C. The polymer stream K was expressed through two nozzles, cooled in a water bath filled with demineralized water, and chopped into pellets by means of a pelletizer 21. When the temperature of polymer stream K was measured, a temperature of 208° C. was determined.

Example 2

[0121] An annular gear pump 2 (HNP, MZR 7255) was used to convey an HDI stream A from a 250 liter tank for HDI 1 to a static mixer 7. The throughput of the HDI stream A was measured using a mass flow meter 3 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 12 kg/h) and adjusted to a value of 4.760 kg/h. An annular gear pump 5 (HNP, MZR 7205) was used to convey a BDO stream B from a 250 liter tank for BDO 4 to the static mixer 7. The throughput of the BDO stream was measured using a mass flow meter 6 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 8 kg/h) and adjusted to a value of 3.000 kg/h. The temperature of the HDI was ambient temperature, about 25° C. The temperature of the BDO was 40° C. In the static mixer 7 (Sulzer SMX, diameter 6 mm, length-to-diameter ratio L/D=10) the HDI stream A and the BDO stream B were mixed with one another. This is stream C.

[0122] The mixed and dispersed stream C is in a circuit mixed with a circulating polymer stream D in an externally temperature-controlled static mixer 8 (static mixer equivalent to Sulzer SMX, internal diameter 34 mm, L/D=20) to afford a stream H. Heat was also already transferred into this static mixer and the heat transfer surface area was 0.05 square meters. The temperature of stream D was 185° C.

[0123] The mixed and already partly reacted stream H was passed into a temperature-controllable static mixer 9. The reaction was largely completed therein and the resulting heat of reaction is 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 2.2 liters and a heat exchange surface area of 0.31 square meters. Under the operating conditions, its heat-exchange capacity based on the product side was 87 watts per kelvin. Based on the total volume of the loop reactor of 4 liters, the heat-transfer coefficient was 22 kilowatts per cubic meter per kelvin. It was heated/cooled with heat-transfer oil. The heating medium temperature at the inlet was 185° C. The total area of the pipe conduits was 0.18 square meters.

[0124] The ratio of the heat transfer surface area to the total surface area was thus (0.31+0.05)/(0.31+0.05+0.18)=0.655.

[0125] The heat-transfer coefficient in the temperature-controllable static mixer was 270 watts per square meter per kelvin.

[0126] The product stream exited the temperature-controllable static mixer 9 as a largely fully-reacted stream E at a temperature of 185° C. At a branching 11, stream E was divided into two substreams F and G. The pressure of substream F was increased in a gear pump 10. Substream F became the abovementioned substream D downstream of the pump.

[0127] The gear pump 10 (Witte Chem 25,6-3) had a volume per revolution of 25.6 cubic centimeters and a speed of 75 revolutions per minute. The pumped stream G thus amounted to 112.5 kg/h.

[0128] The whole circuit was full and the polymer was largely incompressible. The mass flow rate of stream G was therefore identical to that of stream C. Stream G consisted of oligomer.

[0129] The whole circuit consisted of double-walled pipe conduits and apparatuses heated with thermal oil. The heating medium temperature was 185° C.

[0130] The mass flow G was then passed through a pressure control valve 12. The pressure in the pressure control valve 12 was over the course of the test controlled in such a way that a pressure in the circuit was between 4 and 7 bar abs. This resulted in a single-phase flow in the entire circuit without exceeding the pressure resistance of all apparatuses.

[0131] Downstream of the pressure control 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 liter metal vat with extraction. In regular operation, stream G was passed to an extruder 18. The stream at the waste container 14 was sampled under steady-state conditions and the viscosity was 7 Pa.Math.s at 190° C. and a frequency of 10 Hz.

[0132] A micro annular gear pump 15 (MZR 6355 from HNP) was used to withdraw an HDI stream J from the HDI tank 1. The throughput of the HDI stream J was measured using a mass flow meter 16 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 2 kg/h) and adjusted to 0.784 kilograms per hour. The temperature of the HDI stream J was also room temperature, about 25° C. This stream was also passed to the extruder 18.

[0133] The extruder 18 was a ZSK 26 MC from Coperion, which was operated at a speed of 180 revolutions per minute. In this extruder, stream G was freed of any inert gases entrained with material streams A and B and of possible volatile reaction products by means of a venting system 17 operated at a negative pressure of about 1 mbar relative to ambient pressure. Downstream of the addition of the oligomer stream G, the HDI stream J was added and the reaction to afford the polymer was performed. The resulting polymer stream was also freed of volatile constituents via a degassing 19 before the end of the extruder. The pressure in this degassing was 600 mbar below ambient pressure. The barrel temperatures of the extruder were set to between 190° C. and 210° C. The polymer stream K was expressed through two nozzles, cooled in a water bath filled with demineralized water, and chopped into pellets by means of a pelletizer 21. When the temperature of polymer stream K was measured, a temperature of 208° C. was determined.

Example 3

[0134] An annular gear pump 2 (HNP, MZR 7255) was used to convey an HDI stream A from a 250 liter tank for HDI 1 to a static mixer 7. The throughput of the HDI stream A was measured using a mass flow meter 3 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 12 kg/h) and adjusted to a value of 4.591 kg/h. An annular gear pump 5 (HNP, MZR 7205) was used to convey a BDO stream B from a 250 liter tank for BDO 4 to the static mixer 7. The throughput of the BDO stream was measured using a mass flow meter 6 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 8 kg/h) and adjusted to a value of 3.000 kg/h. The temperature of the HDI was ambient temperature, about 25° C. The temperature of the BDO was 40° C. In the static mixer 7 (Sulzer SMX, diameter 6 mm, length-to-diameter ratio L/D=10) the HDI stream A and the BDO stream B were mixed with one another. This is stream C.

[0135] The mixed and dispersed stream C is in a circuit mixed with a circulating polymer stream D in an externally temperature-controlled static mixer 8 (static mixer equivalent to Sulzer SMX, internal diameter 34 mm, L/D=20) to afford a stream H. Heat was also already transferred into this static mixer and the heat transfer surface area was 0.05 square meters. The temperature of stream D was 182° C.

[0136] The mixed and already partly reacted stream H was passed into a temperature-controllable static mixer 9. The reaction was largely completed therein and the resulting heat of reaction is 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 2.2 liters and a heat exchange surface area of 0.31 square meters. Under the operating conditions, its heat-exchange capacity based on the product side was 87 watts per kelvin. Based on the total volume of the loop reactor of 4 liters, the heat-transfer coefficient was 22 kilowatts per cubic meter per kelvin. It was heated/cooled with heat-transfer oil. The heating medium temperature at the inlet was 180° C.

[0137] The ratio of the heat transfer surface area to the total surface area was thus (0.31+0.05)/(0.31+0.05+0.18)=0.655.

[0138] The heat-transfer coefficient in the temperature-controllable static mixer was 270 watts per square meter per kelvin.

[0139] The product stream exited the temperature-controllable static mixer 9 as a largely fully-reacted stream E at a temperature of 183° C. At a branching 11, stream E was divided into two substreams F and G. The pressure of substream F was increased in a gear pump 10. Substream F became the abovementioned substream D downstream of the pump.

[0140] The gear pump 10 (Witte Chem 25,6-3) had a volume per revolution of 25.6 cubic centimeters and a speed of 50 revolutions per minute. The pumped stream G thus amounted to 75 kg/h.

[0141] The whole circuit was full and the polymer was largely incompressible. The mass flow rate of stream G was therefore identical to that of stream C. Stream G consisted of oligomer.

[0142] The whole circuit consisted of double-walled pipe conduits and apparatuses heated with thermal oil. The heating medium temperature was 182° C.

[0143] The mass flow G was then passed through a pressure control valve 12. The pressure in the pressure control valve 12 was over the course of the test controlled in such a way that a pressure in the circuit was between 4 and 9 bar abs. This resulted in a single-phase flow in the entire circuit without exceeding the pressure resistance of all apparatuses.

[0144] Downstream of the pressure control 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 liter metal vat with extraction. In regular operation, stream G was passed to an extruder 18. The stream at the waste container 14 was sampled under steady-state conditions and the viscosity was 2.3 Pa.Math.s at 190° C. and a frequency of 10 Hz.

[0145] A micro annular gear pump 15 (MZR 6355 from HNP) was used to withdraw an HDI stream J from the HDI tank 1. The throughput of the HDI stream J was measured using a mass flow meter 16 (Bronkhorst, Mini Cori-Flow M1X, max. flow rate 2 kg/h) and adjusted to 0.952 kilograms per hour. The temperature of the HDI stream J was also room temperature, about 25° C. This stream was also passed to the extruder 18.

[0146] The extruder 18 was a ZSK 26 MC from Coperion, which was operated at a speed of 66 revolutions per minute. In this extruder, stream G was freed of any inert gases entrained with material streams A and B and of possible volatile reaction products by means of a venting system 17 operated at a negative pressure of about 1 mbar relative to ambient pressure. Downstream of the addition of the oligomer stream G, the HDI stream J was added and the reaction to afford the polymer was performed. The resulting polymer stream was also freed of volatile constituents via a degassing 19 before the end of the extruder. The pressure in this degassing was 200 mbar below ambient pressure. The barrel temperatures of the extruder were set to between 190° C. and 260° C. The polymer stream K was expressed through two nozzles, cooled in a water bath filled with demineralized water, and chopped into pellets by means of a pelletizer 21. When the temperature of polymer stream K was measured, a temperature of 248° C. was determined.