EP4077445A1

EP4077445A1 - Method for producing a thermoplastic polyurethane with a low colour number

Info

Publication number: EP4077445A1
Application number: EP20820209.3A
Authority: EP
Inventors: Thomas König; Mathias Matner; Bernd GARSKA
Original assignee: Covestro Intellectual Property GmbH and Co KG
Current assignee: Covestro Intellectual Property GmbH and Co KG
Priority date: 2019-12-17
Filing date: 2020-12-10
Publication date: 2022-10-26
Also published as: CN114761455A; WO2021122309A1; EP3838946A1

Abstract

The present invention relates to a method for producing a thermoplastic polyurethane with a low colour number, as well as to the thermoplastic polyurethane obtained according to said method and to the use thereof.

Description

Process for the production of a thermoplastic polyurethane with a low color number

The present invention relates to a process for the production of a thermoplastic polyurethane with a low color number and the thermoplastic polyurethane obtained therewith and its use.

Thermoplastic polyurethanes are largely unbranched macromolecules. They are usually obtained by reacting bifunctional isocyanates, long chain diols such as polyethers or polyesters, and chain extenders with one another. There are various technical processes for the production of thermoplastic polyurethane (TPU), a distinction being made between discontinuous batch processes and continuous processes. A continuous process is reactive extrusion, in which the starting materials used for production are fed into an extruder. The reactive extrusion has to be differentiated from the use of an extruder for the pure processing of plastics. In reactive extrusion, the starting materials are mixed by the rotary movements of the screw of the extruder and react with one another, so that a polymer melt is obtained. This polymer melt is then extruded and the extrudate strands obtained, possibly after cooling in a water bath, cut into granules or brought directly into a specific shape. When processing TPU in an extruder, granules made from already synthesized TPU are melted in the extruder and the melt is extruded.

If a TPU is melted again, inhomogeneities can arise in the polymer melt when it is melted because part of the granulate has already melted but another part has not yet melted. Inhomogeneous polymer melts pose problems during processing in the extruder because unmelted, largely solid or gel-like parts move more slowly in the extruder than already melted TPU, which forms a largely liquid or viscous polymer melt. The largely solid parts can also collect in the extruder and loosen again in batches and lead to contamination of the polymer melt.

Polyurethanes that are built up from short-chain aliphatic diols and aliphatic polyisocyanates have properties that are comparable or better than those of polyamide plastics. Up to now, however, they have not been able to be produced satisfactorily on an industrial scale, since decisive process engineering problems have not yet been solved. Due to the high density of reactive groups, the polyaddition of short-chain aliphatic diols with aliphatic polyisocyanates has a high degree of heat or enthalpy of reaction, which is at Insufficient heat dissipation leads to damage up to and including the regression of monomers and destruction (incineration) of the polyurethane.

CN 10714 1437 refers to TPU that is to be used in 3D printing processes. The document discloses a synthesis by reactive extrusion and teaches that the enthalpy of fusion of a TPU can be influenced by the addition of a chain extender, the chain extender being a cyclodextrin derivative.

CN 10500 1626 also discloses a process for reactive extrusion of polyurethane. The publication discloses that the flow properties of the TPU can be influenced by adding a mixture of diphenylsilylglycol and ethylene glycol.

US 2017/145146 refers to TPU made from components that come from renewable, vegetable resources. The publication discloses the synthesis in a batch process and teaches that the melting temperature of a TPU depends, among other things, on the isocyanate index and the polymerization time.

DE728981 and US2511544 disclose a batch process for converting diisocyanates with diols and / or diamines to form polyurethane or polyureas in a solvent-based or solvent-free process.

The disadvantage of the batch processes described above is that they are difficult to upscale from the pilot plant scale. Above all, in systems that have a high exothermic warming of the reaction with a reaction enthalpy of <-500 kJ / kg, the adiabatic temperature rise and the dissipation of heat are problematic due to the significantly smaller ratio of the available cooling surface to that on a large scale Volume of the product, insufficient. Starting from monomers at a temperature sufficient for an uncatalyzed start of the reaction (> 50 ° C.), the temperature of the reaction products would rise to well above 300 ° C. in the adiabatic mode of operation. The production and processing of polyurethanes at temperatures of> 200 ° C leads to a loss of quality due to a large number of thermal side reactions. Product temperatures that are too high can in principle be prevented by a batch procedure in which at least one of the two monomers is slowly metered in, depending on the cooling capacity of the reactor. Cooling of highly viscous polymers in batch devices is, however, technically limited by the surface of the heat exchanger and the flow rate. Long residence times in combination with high temperatures increase the number of undesirable side reactions and have a detrimental effect on the product properties. On top of that, Due to the increase in viscosity during the polymerization, process engineering problems arise, such as difficult or impossible delivery of the polymer from the batch apparatus.

The object of the present invention is to provide a process for the production of a thermoplastic polyurethane with a low color number which enables polyaddition reactions to be carried out with a large negative enthalpy of reaction per kg of reaction mass on an industrial scale.

This object was achieved by a method for producing a thermoplastic polyurethane by means of reactive extrusion by reacting the components

A) one or more aliphatic diols, the total amount of component A) having an average molecular weight in the range from 62 g / mol to 120 g / mol,

B) 1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI) and / or mixtures of at least 2 of these,

C) optionally one or more catalysts, and

D) optionally further auxiliaries or additives, characterized in that it comprises the following steps: a) discontinuous production of OH-functional prepolymers from a partial amount of component A) or the total amount of component A), preferably the total amount of component A) with a partial amount of component B), the molar ratio of component A) to component B) being from 1.0: 0.75 to 1.0: 0.95, b) optionally isolating the OH-functional prepolymers from step a ), c) Reacting the OH-functional prepolymers with a further partial amount of component B) and optionally a further partial amount of component A), preferably only with a further partial amount of component B), in an extruder to obtain the thermoplastic polyurethane as an extrudate, wherein steps a) and / or c) optionally in the presence of the total amount or a partial amount of component C) and / or the total amount or a partial amount of the component nente D) are carried out, the sum of all subsets of component B) or the sum of all subsets of component C), or the sum of all subsets of component D) over all process steps of the total amount of component B) or the total amount of component C) or the total amount of component D).

It has surprisingly been found that with the reactive extrusion process according to the invention with upstream discontinuous production of a prepolymer, a thermoplastic Polyurethane is obtained which has a low color number, ie there is hardly any damage to the product. By combining discontinuous production in a batch apparatus with reactive extrusion, thermoplastic polyurethane can be continuously produced, which can be obtained by a polyaddition reaction with a large negative enthalpy of reaction per kg of reaction mass.

In the context of the present invention, an “OH-functional prepolymer” is understood to mean a prepolymer mixture in which at least 90% by number of the molecule ends have a hydroxyl group and the remaining 10% by number of molecule ends have further hydroxyl groups, NCO groups and / or not - have reactive groups. In the context of the present invention, a “non-reactive group” is understood to mean a group which, under the reaction conditions according to the invention, reacts neither with NCO groups nor with OH groups during the reaction. A non-reactive group can, for example, be converted from a reactive NCO group or OH group into a non-reactive group by reacting with suitable reaction partners (chain terminators). Suitable chain terminators are all monofunctional compounds which react either with an isocyanate group or with a hydroxyl group under the reaction conditions according to the invention, for example monoalcohols such as methanol, monoamines such as diethylamine and monoisocyanates such as butyl isocyanate. The OH-functional prepolymer can, for example, have a hydroxyl group at one end of the molecule and, for example, an alkyl group at the other end of the molecule. When an OH-functional prepolymer is spoken of in the context of the present invention, this also always includes a mixture of the at least one OH-functional prepolymer and a non-reactively terminated prepolymer.

The word “a” in connection with countable quantities is only to be understood as a numerical word within the scope of the present invention if this is expressly stated (for example by the expression “exactly one”). If, for example, “a polyol” is used in the following, the word “a” is only to be understood as an indefinite article and not as a numerical word, so it also encompasses an embodiment that contains a mixture of at least two polyols.

According to the invention, the terms “comprising” or “containing” preferably mean “essentially consisting of” and particularly preferably “consisting of”.

In step a) of the process according to the invention, the OH-functional prepolymers are produced in a batch process. For this purpose, a partial amount of component A) is mixed with a partial amount of component B) or from the total amount of component A) with a partial amount of component B) the OH-functional prepolymers are produced, with a molar ratio of component A) to component B) of 1.0: 0.75 to 1.0: 0.95 being present. The reaction typically takes place under temperature control in a reaction vessel such as a double-walled stirred tank, a stirred tank with an internal cooling device or a stirred tank with an external cooling circuit, for example consisting of a circulation pump and a heat exchanger. The reaction is preferably carried out without a solvent. The OH-functional prepolymers are formed by the reaction of the monomers of components A) and B) both with one another and with oligomeric reaction products of these monomers already present in the reaction vessel.

In the context of the present invention, a “solvent-free process” or “solvent-free” is understood to mean the reaction of components A and B without additional diluents, such as organic solvents or water, i.e. components A and B are preferably reacted with one another undiluted. Components C and / or D can optionally be present in suitable diluents and added to components A and / or B as a solution. The process in the context of the present invention is still to be regarded as solvent-free if the content of the solvent is up to 1% by weight, preferably up to 0.1% by weight, more preferably up to 0.01% by weight, based on the total weight of the reaction mixture. A solvent is understood to mean a substance in which at least one of components A and B and optionally C and / or D can be dissolved, dispersed, suspended or emulsified, but which cannot be mixed with one of components A and B and optionally C and / or D or the OH-functional prepolymer (s) reacts.

Furthermore, components A) and B) can be mixed with one another before entering the reaction vessel, for example by means of a static mixer. As component A), preference is given to using 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol and / or mixtures of at least 2 thereof, and more preferably 1,4-butanediol. 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI) and / or mixtures thereof are preferably used as component B) and 1,6-diisocyanatohexane (HDI) is even more preferably used as component B). Before being introduced into the reaction vessel, component B) preferably has a temperature of from 20 ° C. to 25 ° C. and, independently of this, component A) preferably has a temperature of from 35 ° C. to 45 ° C.

Component A) is preferably initially introduced into the reaction vessel and component B) is slowly added. The reaction can be carried out in the presence of components C) and / or D). The total amount or a partial amount of components C) and / or D) can be used be mixed with component A) and / or B). In a preferred embodiment, component C) is mixed with component A) before component B) is added to this mixture. In another preferred embodiment, components A) and B) are reacted with one another without components C) and / or D). The conversion of components A) and B) to the OH-functional prepolymers is preferably carried out at a temperature from 40 ° C to 260 ° C, particularly preferably at a temperature from 70 ° C to 220 ° C. It is possible that the temperature is increased as the reaction progresses, ie at the beginning of the reaction there is a lower temperature, for example a temperature of 40 ° C to 70 ° C, which is then increased as the reaction progresses, for example to 180 ° C up to 260 ° C. This has the advantage that the heat of reaction released is used to heat the reaction mixture and the temperature can be better controlled. The container can also be heated to increase the temperature.

In step b), the OH-functional prepolymers produced in step a) are optionally isolated. Since the OH-functional prepolymers are stable on storage at room temperature (20 ° C) due to their solid state of aggregation, they can be isolated, for example, by transferring them to a suitable storage tank or by filling them into suitable containers, and if necessary they can be melted again and fed into the manufacturing process.

In step c), the OH-functional prepolymers are reacted with a further subset of component B) and optionally a further subset of component A), preferably only with a further subset of component B), in an extruder to obtain the thermoplastic polyurethane as an extrudate . In the extruder, the movements of the conveying elements inside the extruder both mix the components and convey them downstream in the extruder working direction towards an outlet opening of the extruder. The components react with one another in a continuous process, so that the thermoplastic polyurethane is obtained. The viscosity of the components located in the extruder preferably increases in the extruder working direction as the degree of polymerization progresses. In the area of the inlet openings for the OH-functional prepolymers and component B) and optionally component A) there is preferably a mixture with a low viscosity in the extruder, which can be referred to as a liquid, while shortly before it exits the extruder, preferably a polymer melt is present, which has a higher viscosity than the OH-functional prepolymers and components B) and optionally A) and can be referred to as viscous. The extruder is preferably a self-cleaning machine, particularly preferably a co-rotating twin-screw extruder or a planetary roller extruder. Such extruders are the Known to those skilled in the art and described, for example, in K. Kohlgrüber (editor), The co-rotating twin-screw extruder, ISBN 978-3-446-41252-1, page 1.

In a preferred embodiment of the process according to the invention, the reaction in step c) is carried out at a temperature from 150.degree. C. to 260.degree. C., preferably from 180.degree. C. to 240.degree. It is tolerated that the product experiences short-term (<60 seconds) deviations in the reaction temperature from the above-mentioned ranges during implementation.

In a preferred embodiment of the process according to the invention, the reaction in the extruder in step c) takes place continuously or batchwise, the reaction in the extruder in step c) preferably taking place continuously.

In a preferred embodiment of the process according to the invention, the further partial amount of component B) and optionally the further partial amount of component A) are introduced into the extruder in step c) in the extruder working direction downstream of the introduction of the OH-functional prepolymers.

The OH-functional prepolymers are preferably introduced into the extruder in step c) on the inlet side of the extruder. Before the OH-functional prepolymers are introduced into the extruder, gases and gaseous by-products are preferably removed from the OH-functional prepolymers. In a preferred embodiment, gases and gaseous by-products are removed by passing the OH-functional prepolymers through a venting device with a negative pressure of 0.1 mbar to 500 mbar under normal pressure, the venting device preferably being arranged on the extruder. The removal of gases and gaseous by-products is preferably carried out by means of atmospheric degassing, i.e. by means of a venting device which is arranged on the extruder, without the application of a negative pressure. In a further preferred embodiment of the method according to the invention, before the OH-functional prepolymers are introduced into the extruder in step c), gases and gaseous by-products are removed from the OH-functional prepolymers, particularly preferably by passing the OH-functional prepolymers through a venting device, even more preferably at a negative pressure of 50 mbar to 500 mbar under normal pressure, the venting device preferably being arranged on the extruder.

In a preferred embodiment of the method according to the invention, gases and gaseous by-products are removed from the thermoplastic polyurethane by applying a negative pressure of 50 mbar to 500 mbar, more preferably from 80 mbar to 300 mbar, even more preferably from 100 mbar to 250 mbar, in each case under normal pressure created a degassing shaft which is preferably arranged in the last third of the extruder in the extruder working direction. For this purpose, a degassing dome is preferably arranged on the degassing shaft.

In a preferred embodiment of the method according to the invention, a degassing extruder is arranged in the degassing shaft, on which there is a vacuum dome and a negative pressure of 300 mbar to 500 mbar under normal pressure is applied. The vented extruder is preferably a short twin-screw extruder in which the direction of rotation of the screws or spindles is set so that they return polymer melt or thermoplastic polyurethane, which is drawn from the extruder into the vented shaft by the negative pressure, back into the extruder .

In a further embodiment, a retaining device is arranged in the venting shaft of the extruder, on which there is a vacuum dome and a negative pressure of 250 mbar to 350 mbar, more preferably 280 mbar to 320 mbar, in each case under normal pressure. In this embodiment, a twin screw extruder or planetary roller extruder is used to carry out the process and the opening of the degassing shaft to the extruder has an elongated shape and is perpendicular to the axis of the twin screws or to the axis of the central spindle, so that part of both twin screws or . the planetary spindles is covered. The retaining device is preferably designed so that its opening oriented towards the extruder covers the area of the turning screw or spindle and the gusset, so that in this area no polymer melt or thermoplastic polyurethane is drawn into the degassing shaft by the negative pressure from the extruder, can penetrate. Above the uncovered area of the opening of the retaining device, a shaft preferably leads obliquely against the direction of rotation of the uncovered screw or spindle in the direction of the vacuum dome. Polymer melt or thermoplastic polyurethane, which is drawn into the retaining device, bounces off the inclined shaft and falls back into the extruder and is drawn back into the extruder by the rotary movement of the screws or spindles in the extruder. The area of engagement of the two screws is referred to as the gusset. In twin-screw extruders, the two screw elements do not touch, but are designed so that they intermesh. The area of engagement of the two snails is called the gusset. The screw whose rotational movement is directed away from the housing of the extruder to the area between the two axes of the screw elements is referred to as the unwinding screw.

In the context of the invention, normal pressure is understood to mean a pressure of 101 325 Pa = 1.013 25 bar. Steps a) and / or c) can, if appropriate, be carried out in the presence of the total amount or a partial amount of component C) and / or the total amount or a partial amount of component D). The sum of all subsets of component B) or the sum of all subsets of component C), or the sum of all subsets of component D) over all process steps corresponds to the total amount of component B) or the total amount of component C) , or the total amount of component D).

The method according to the invention preferably comprises the following additional steps: f) cooling the thermoplastic polyurethane to a temperature below its melting point in a cooling device, the cooling device preferably being a water bath, g) comminuting the thermoplastic polyurethane in a comminuting device.

As a result of the cooling of the thermoplastic polyurethane, a solid is obtained which is preferably comminuted into granules in the comminution device. These granules can be melted in an extrusion process for further processing and the polymer melt obtained by the melting can be processed into a molded part, for example by injection into a mold.

One or more aliphatic diols can be used as component A) in the process according to the invention. All aliphatic diols known to the person skilled in the art are suitable as aliphatic diols. These can be, for example, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol and 1,12-dodecanediol. The total amount of component A) used in the process must, however, have an average molecular weight in the range from 62 g / mol to 120 g / mol. The aliphatic diols used as component A) in the process according to the invention and / or its precursor compounds can have been obtained from fossil or biological sources.

In a preferred embodiment of the process according to the invention, component A) is selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1, 4-butanediol, 1,5-pentanediol, 1,6-hexanediol and / or mixtures of at least 2 thereof, preferably selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1 , 2-butanediol, 1,3-butanediol, 1,4-butanediol and / or mixtures of at least 2 thereof, particularly preferably selected from the group consisting of 1,2- Ethanediol, 1,3-propanediol, 1,4-butanediol, and / or mixtures of at least 2 of these, and more preferably 1,4-butanediol is used as component A).

In the process according to the invention, 1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI) and / or mixtures of at least two of these can be used as component B). Preference is given to using 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI) and / or a mixture thereof. 1,6-Diisocyanatohexane (HDI) is particularly preferably used as component B). The diisocyanates used as component B) in the process according to the invention and / or their precursor compounds can have been obtained from fossil or biological sources. 1,6-Diisocyanatohexane (HDI) is preferably produced from 1,6-hexamethylenediamine and 1,5-diisocyanatopentane from 1,5-pentamethylenediamine, 1,6-hexamethylenediamine and 1,5-pentamethylenediamine from biological sources, preferably by bacterial fermentation , be won.

In a preferred embodiment of the process according to the invention, 1,4-butanediol is used as component A) and 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI) and / or mixtures thereof are used as component B); A) 1,4-butanediol and 1,6-diisocyanatohexane (HDI) as component B).

One or more catalysts can be used as component C). Suitable catalysts according to the invention are the conventional tertiary amines known from the prior art, such as. B. triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N, N'-dimethyl-piperazine, 2- (dimethylaminoethoxy) -ethanol, diazabicyclo- (2,2,2) -octane and similar, and in particular organic metal compounds such as titanic acid esters, iron compounds, Tin compounds, for example tin diacetate, tin dioctoate, tin dilaurate or the tin dialkyl salts of aliphatic carboxylic acids such as dibutyl tin diacetate, dibutyl tin dilaurate or the like. Preferred catalysts are organic metal compounds, in particular titanic acid esters, iron and / or tin compounds.

The catalyst is used in amounts from 0.001% by weight to 2.0% by weight, preferably from 0.005% by weight to 1.0% by weight, particularly preferably from 0.01% by weight to 0.1% by weight .-% based on the diisocyanate component B used. The catalyst can be used as such or dissolved in the diol component A. One advantage here is that the thermoplastic polyurethanes then obtained do not contain any impurities from any catalyst solvents used. The catalyst can be added in one or more portions or continuously, e.g. B. with the help of a suitable metering pump over the entire duration of the implementation. Alternatively, however, it is also possible to use mixtures of the catalyst (s) with a catalyst solvent, preferably with an organic catalyst solvent. The degree of dilution of the catalyst solutions can be chosen freely within a very broad range. Solutions with a concentration of 0.001% or more are catalytically effective.

Suitable catalyst solvents are, for example, solvents which are inert towards isocyanate groups, such as, for example, hexane, toluene, xylene, chlorobenzene, ethyl acetate, butyl acetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monomethyl or methyl ether acetate, diethylene glycol ethyl acetate and propylene glycol ether oxyethyl ether, 1 ethylene glycol mono-propyl acetate, 1-ethylene glycol mono-propylene acetate, 1-ethylene glycol acetate, 1-ethylene glycol mono-propyl ether -2-acetate, 3-methoxy-n-butyl acetate, propylene glycol diacetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, lactones such as ß-propiolactone, g-butyrolactone, e-caprolactone and e-methylcaprolactone, but also solvents such as N- Methylpyrrolidone and N-methylcaprolactam, 1,2-propylene carbonate, methylene chloride, dimethyl sulfoxide, triethyl phosphate or any mixtures of such solvents.

In the process according to the invention, however, it is also possible to use catalyst solvents which carry groups which are reactive toward isocyanates and which can be incorporated into the diisocyanate. Examples of such solvents are mono- or polyhydric simple alcohols, such as. B. methanol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, the isomeric butanediols, 2-ethyl-1,3-hexanediol or glycerol; Ether alcohols, such as. B. l-methoxy-2-propanol, 3-ethyl-3-hydroxymethyloxetane, tetrahydrofurfuryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol mono-methyl ether, diethylene glycol mono-methyl ether, diethylene glycol mono-glycol ethers, liquid mixed glycols, diethylene glycol mono-ethylene glycols, diethylene glycol mono-ethylene glycols, and also poly-propylene glycols, diethylene glycol monob

Polyethylene / polypropylene glycols and their monoalkyl ethers; Ester alcohols, such as. B. ethylene glycol monoacetate, propylene glycol monolaurate, glycerol mono- and diacetate, glycerol monobutyrate or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate; unsaturated alcohols such as. B. allyl alcohol, 1,1-dimethyl-allyl alcohol or oleic alcohol; araliphatic alcohols such as. B. benzyl alcohol; N-monosubstituted amides, such as. B. N-methylformamide, N-methylacetamide, cyanoacetamide or 2-pyrrolidinone or any mixtures of such solvents.

Auxiliaries and additives can also be used as component C) in the process according to the invention. These can be, for example, additives common in the field of thermoplastic technology, such as dyes, fillers, processing aids, plasticizers, nucleating agents, stabilizers, flame retardants, mold release agents or reinforcing additives. More detailed information on the auxiliaries and additives mentioned can be found in the specialist literature, for example the monograph by JH Saunders and KC Frisch "High Polymers ", Volume XVI, Polyurethane, Part 1 and 2, Verlag Interscience Publishers 1962 and 1964, the pocket book for plastic additives by R. Gächter and H. Müller (Hanser Verlag Munich 1990) or DE-A 29 01 774 It can of course also be advantageous to use several additives of several types.

In another preferred embodiment, conventional isocyanate-reactive mono-, di-, tri- or polyfunctional compounds in proportions of 0.001 mol% to 2 mol%, preferably 0.002 mol% to 1 mol%, can also be obtained as additives in small amounts on the total amount of the component A, z. B. can be used as chain terminators, auxiliaries or mold release agents. Examples include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol , n-octadecanol, cyclohexanol and stearyl alcohol. Examples of suitable triols are trimethylolethane, trimethylolpropane or glycerol. Suitable higher-functional alcohols are ditrimethylolpropane, pentaerythritol, dipentaerythritol or sorbitol. Amines such as butylamine and stearylamine or thiols are also suitable.

In a preferred embodiment of the process according to the invention, the total enthalpy of reaction resulting exclusively in process steps a) and c) for an equimolar reaction of component A) with component B) is in the range from -900 kJ / kg to -500 kJ / kg, determined according to DIN 51007: 1994-06, preferably in the range from -900 kJ / kg to -550 kJ / kg, particularly preferably in the range from -900 kJ / kg to -580 kJ / kg, more preferably in the range from -900 kJ / kg to - 600 kJ / kg, more preferably in the range from -900 kJ / kg to -650 kJ / kg.

In the context of the present invention, “total reaction enthalpy” is understood to mean the mass-specific change in enthalpy that takes place exclusively in process steps a) and c) for an equimolar reaction of component A) with component B), in particular without dilution. The enthalpy of reaction is given in kJ per kg of the total reaction mixture of component A and component B, with a molar ratio of component A to component B of 1.0: 1.0. A reaction with a negative enthalpy of reaction is described as an exothermic reaction, which means that energy is released in the form of heat during the reaction.

In a preferred embodiment of the process according to the invention, 25% to 98%, preferably 30% to 95%, particularly preferably 40% to 90%, very particularly preferably 50% to 80% of the total enthalpy of reaction is removed in step a). This has the advantage that the maximum heat released by the resulting TPU can be controlled during the production process and thus narrower temperature limits can be adhered to. In a preferred embodiment of the process according to the invention, overall, ie over all process stages, there is a molar ratio of component A) to component B) of 1.0: 0.95 to 0.95: 1.0.

Another embodiment of the invention relates to a thermoplastic polyurethane obtainable or obtained by the process according to the invention. The thermoplastic polyurethane according to the invention

In a preferred embodiment, the L * value of the thermoplastic polyurethane according to the invention, measured in the CIELab color space with the light type D 65, is between 80 and 100 and the b * value is between -0.5 and 1.5, preferably the L * Value between 80 and 100 and the b * value between -0.5 and 1.0.

In a further embodiment, the invention relates to the use of the thermoplastic polyurethane according to the invention in a molding process with melting of the thermoplastic polyurethane, in particular for the production of interior components for vehicles.

In a further embodiment, the invention relates to a composition which comprises at least one thermoplastic polyurethane polymer according to the invention and at least one additive or another thermoplastic polymer.

The additive can be, for example, additives common in the field of thermoplastic technology, such as dyes, fillers, processing aids, plasticizers, nucleating agents, stabilizers, flame retardants, mold release agents or reinforcing additives. More detailed information on the additives mentioned can be found in the specialist literature, for example the monograph by J.H. Saunders and K.C. Frisch "High Polymers", Volume XVI, Polyurethane, Part 1 and 2, Interscience Publishers 1962 and 1964, the pocket book for plastic additives by R. Gächter and H. Müller (Hanser Verlag Munich 1990) or DE-A 29 01 774. It can of course also be advantageous to use several additives of several types.

Suitable thermoplastic polymers that can be part of the composition according to the invention are, for example, polystyrenes, polyamides, polyethylene, polypropylene, polyacrylates, polymethacrylates, polyurethanes or acrylonitrile-butadiene-styrene copolymers (ABS).

Thermoplastic molding compounds can be produced from the compositions according to the invention. The invention therefore also relates to a thermoplastic Molding composition which comprises at least one composition according to the invention. The thermoplastic molding compositions according to the invention can be prepared, for example, by mixing the respective constituents of the compositions in a known manner and at temperatures of preferably 180 ° C to 320 ° C, particularly preferably at 200 ° C to 300 ° C in conventional units such as internal kneaders, Melt compounded and melt extruded extruders and twin screw screws. This process is generally referred to as compounding in the context of this application.

Molding compound is understood to mean the product that is obtained when the constituents of the composition are melt-compounded or melt-extruded.

The individual constituents of the compositions can be mixed in a known manner, both successively and simultaneously, both at about 20 ° C. (room temperature) and at a higher temperature. This means that, for example, some of the constituents can be dosed via the main intake of an extruder and the remaining constituents can be fed in later in the compounding process via a side extruder.

The invention also relates to a process for producing the molding compositions according to the invention.

The thermoplastic molding compositions according to the invention can be used to produce moldings, films and / or fibers of all types. The invention therefore also provides a molded article, a film and / or a fiber, the molded article, the film or the fiber comprising at least one thermoplastic polyurethane polymer according to the invention, at least one thermoplastic molding compound according to the invention or at least one composition according to the invention. These can be produced, for example, by injection molding, extrusion, blow molding and / or melt spinning. Another form of processing is the production of moldings by deep drawing from previously produced sheets or foils.

It is also possible to meter the constituents of the compositions directly into an injection molding machine or into an extrusion unit and process them into molded articles.

Another object of the invention is the use of a thermoplastic polyurethane polymer according to the invention for producing a composition or a thermoplastic molding material.

Another object of the invention is the use of an inventive

Composition for the production of a thermoplastic molding compound.

Another object of the invention is the use of a thermoplastic polyurethane polymer according to the invention, a thermoplastic molding composition according to the invention or a composition according to the invention for producing a shaped body, a film and / or a fiber.

The illustration explained below serves to explain the invention in more detail, whereby these merely represent illustrative examples for certain embodiments, but do not limit the scope of the invention:

Figure 1: a preferred device for performing the method according to the invention.

Examples

The present invention is further illustrated by the following examples, without, however, being restricted thereto.

Unless otherwise stated, all percentages relate to weight.

Used raw materials:

1,6-Diisocyanatohexane (HDI) was obtained from Covestro AG.

1,4-Butanediol (BDO) was obtained from Ashland.

Both raw materials had a purity of> 99%.

Color values

The color values in the CIE-Fab color space were determined with a Konica Minolta CM5 spectrophotometer, with the Fichtart D 65, with 10 ° observer according to DIN EN ISO 11664-1 (July 2011).

Differential Scanning Calorimetry (DSC)

The melting point was determined by means of DSC (differential scanning calorimetry) with a Mettler DSC 12E (Mettler Toledo GmbH, Giessen, DE) in accordance with DIN EN 61006 (November 2004). Calibration was carried out using the temperature of the melting onset of indium and lead. 10 mg of substance were weighed into normal capsules. The measurement was carried out by three heatings 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. The cooling was carried out with liquid nitrogen. Nitrogen was used as the purge gas. The values given are based on the evaluation of the 2nd heating curve.

Screening differential thermal analysis (DTA)

The enthalpy data was determined by means of a screening DTA and carried out in an ISO 17025 accredited laboratory. The samples were weighed into glass ampoules, sealed gas-tight and heated in the measuring device at 3 K / min from -50 ° C to +450 ° C. The difference between the sample temperature and the temperature of an inert reference (aluminum oxide) was determined by means of thermocouples. The initial weight was 20 mg - 30 mg. All measurements were carried out in accordance with DIN 51007 (June 1994). The measurement error of the device is ± 2%.

Table 1: Reaction enthalpies determined experimentally by means of DTA. The molar ratio of diisocyanate component to diol component in the determinations is 1.0: 1.0.

Comparative example 1:

1,4-Butanediol (1.35 kg) were placed under nitrogen (1 bar) in a pressure vessel made inert with nitrogen and equipped with anchor stirrer, bottom drain and internal thermometer, and the mixture was stirred until an internal temperature of 90 ° C. was reached. The total amount of 1,6-diisocyanatohexane was then continuously metered into the pressure vessel (2.5 kg) over a period of 2 hours, while the reactor temperature was continuously increased to 190 ° C. at the same time. The temperature of the reaction mixture was due to the heat of reaction liberated by the polyaddition over the entire reaction time up to 15 ° C above the respective specified reactor temperature. After the addition of 1,6-diisocyanatohexane was complete, the mixture was stirred at 200 ° C. for a further 10 minutes. During this time, an increase in viscosity to 106 Pa * s (frequency of 1 Hz, rheometer: Anton Paar MCR-302; measurement according to ISO 6721-10 (September 2015)) was detected. This increase in viscosity resulted in failure of the stirrer. Due to the high viscosity, it was not possible to discharge the polymer from the pressure vessel.

The melting point of the polymer is 174.9 ° C. (DSC 2nd heating after cooling at 20 K / min). The L * value is 84.4, the b * value is 2.

Example according to the invention (Figure 1):

Figure 1 shows schematically the structure for carrying out the two-stage continuous production of a thermoplastic polyurethane.

From the diol storage container 1, which was on the first balance 3, 13.955 kg 1,4-butanediol were conveyed with the pump 4 through the diol line 24 into the stirred reactor 7. reactor 7 was double-walled and could be tempered by thermostats with heat transfer oil. The temperature in reactor 7 was set to 80 ° C. and controlled via temperature sensor 11. Subsequently, within 3 hours, 22.920 kg of 1,6-diisocyanatohexane were conveyed through the diisocyanate line 25 into the reactor 7 from the diisocyanate storage container 2, which was located on the balance 5, with continuous stirring. The hydrostatic pressure difference between the diisocyanate storage container 2 and the reactor 7 was used for the promotion. By the end of the metering of the hexamethylene diisocyanate, the temperature measured by the temperature sensor 8 or 11 rose to 190 ° C. The rise in temperature was limited by manual adjustment of the metering rate of the hexamethylene diisocyanate to a maximum of 20 K within 30 minutes. The heating of the reactor 7 was readjusted during the metering in accordance with the temperatures measured by the temperature sensors 8 and 11 and was 195 ° C. at the end of the metering process. In this step 54% of the total heat of reaction was removed.

The OH-functional prepolymer obtained was then conveyed with the aid of the pump 12 through the prepolymer feed line 27 into the planetary roller extruder 21. The second pump 12 and the prepolymer feed line 27, which connected the reactor 7 and planetary roller extruder 21, could be heated and were kept at a temperature of 200.degree. The planetary roller extruder 21 was a PWE 50 ENTEX Rust & Mitschke GmbH. The flow rate of the OH-functional prepolymer was set to 5 kg / h with the aid of the mass flow meter 13. The OH-functional prepolymer was metered into the planetary roller extruder 21 at the intake 28. Furthermore, 424 g / h of hexamethylene diisocyanate were conveyed from the diisocyanate storage container 16 with the aid of the pump 17 and controlled by the mass flow meter 18 through the diisocyanate line 29 into the planetary roller extruder 21. The temperature in the planetary roller extruder 21 was measured by the temperature sensors 15, 19 and 20 and set to a temperature of 210 ° C. with the aid of an oil thermostat. The speed of the planetary roller extruder 21 was 150 rpm.

The resulting milky-white product was discharged through the extruder nozzles, drawn off as a strand, cooled in a water bath 22 (25 ° C.) and granulated in the granulator 23.

The mean residence time in the planetary roller extruder is approx. 5 minutes.

The melting point of the polymer produced is 179.7 ° C. (DSC 2nd heating after cooling at 20 K / min). The L * value is 81.7, the b * value is 0.4. List of reference symbols

(1) Diol storage container

(2) first diisocyanate storage tank

(3) first scale

(4) first pump

(5) second scale

(6) Solvent storage tank

(7) reactor

(8) first temperature sensor

(9) Drive for stirrer (30)

(10) second pump

(11) second temperature sensor

(12) second pump

(13) first mass flow meter

(14) Drive for planetary roller extruder (21)

(15) third temperature sensor

(16) second diisocyanate storage tank

(17) third pump

(18) second mass flow meter

(19) fourth temperature sensor

(20) fifth temperature sensor

(21) Planetary roller extruder

(22) water bath

(23) granulator

(24) Diole line

(25) first diisocyanate line

(26) Solvent supply line

(27) prepolymer feed line

(28) Extruder feed

(29) second diisocyanate line

(30) stirrer

Claims

1. A process for producing a thermoplastic polyurethane by means of reactive extrusion by reacting components A) one or more aliphatic diols, the total amount of component A) having an average molecular weight in the range from 62 g / mol to 120 g / mol,

C) optionally one or more catalysts, and D) optionally further auxiliaries or additives, characterized in that it comprises the following steps: a) discontinuous production of OH-functional prepolymers from a partial amount of component A) or the total amount of component A ), preferably the total amount of component A) with a partial amount of component B), with a molar ratio of component A) to component B) of 1.0: 0.75 to 1.0: 0.95, b) optionally Isolating the OH-functional prepolymers from step a), c) reacting the OH-functional prepolymers with a further subset of component B) and optionally a further subset of component A), preferably only with a further subset of component B), in one Extruder under

Obtaining the thermoplastic polyurethane as an extrudate, steps a) and / or c) optionally being carried out in the presence of the total amount or a partial amount of component C) and / or the total amount or a partial amount of component D), the sum of all partial amounts of the Component B) or the sum of all subsets of component C), or the sum of all subsets of component D) over all process steps of the total amount of component B), or the total amount of component C), or the total amount of component D ) corresponds.

2. The method according to claim 1, characterized in that the reaction in the extruder in step c) takes place continuously or batchwise, the reaction in the extruder in step c) preferably taking place continuously.

3. The method according to claim 1 or 2, characterized in that the introduction of the further subset of component B) and optionally the further subset of Component A) takes place in the extruder in step c) in the extruder working direction downstream of the introduction of the OH-functional prepolymers.

4. The method according to any one of claims 1 to 3, characterized in that before the introduction of the OH-functional prepolymers into the extruder in step c) gases and gaseous by-products are removed from the OH-functional prepolymers, preferably by the OH-functional prepolymers be passed through a venting device, preferably at a negative pressure of 50 mbar to 500 mbar under normal pressure, the venting device preferably being arranged on the extruder. 5. The method according to any one of claims 1 to 4, characterized in that the reaction in step c) at a temperature of 150 ° C to 260 ° C, preferably from 180 ° C to 240 ° C is carried out.

Process according to one of claims 1 to 5, characterized in that gases and gaseous by-products are removed from the thermoplastic polyurethane by applying a negative pressure of 50 mbar to 500 mbar under normal pressure to a degassing shaft, which is preferably in the last third of the extruder in the extruder working direction is arranged.

7. The method according to any one of claims 1 to 6, characterized in that the method comprises the following additional steps: d) cooling the thermoplastic polyurethane below its melting point in a

Cooling device, e) comminution of the thermoplastic polyurethane in a comminution device.

8. The method according to any one of claims 1 to 7, characterized in that component A) is selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and / or mixtures of at least 2 thereof, preferably selected from the group consisting of 1,2-ethanediol, 1,2- Propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and / or mixtures of at least 2 thereof, particularly preferably selected from the group consisting of 1,2-ethanediol, 1 , 3-propanediol, 1,4-butanediol, and / or mixtures of at least 2 of these, and more preferably 1,4-butanediol.

9. The method according to any one of claims 1 to 8, characterized in that as component A) 1,4-butanediol and as component B) 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI) and / or mixtures are used from this, preferably 1,4-butanediol as component A) and 1,6-diisocyanatohexane (HDI) as component B).

10. The method according to any one of claims 1 to 9, characterized in that the total enthalpy of reaction resulting exclusively in process steps a) and c) for an equimolar reaction of component A) with component B) is in the range of

-900 kJ / kg to -500 kJ / kg, determined according to DIN 51007: 1994-06, preferably in the range from -900 kJ / kg to -550 kJ / kg, particularly preferably in the range from -900 kJ / kg to - 580 kJ / kg, more preferably in the range from -900 kJ / kg to -600 kJ / kg, even more preferably in the range from -900 kJ / kg to -650 kJ / kg. 11. The method according to any one of claims 1 to 10, characterized in that in step a) 25

% to 98% of the total enthalpy of reaction is removed, preferably 30% to 95%, particularly preferably 40% to 90%, very particularly preferably 50% to 80%.

12. The method according to any one of claims 1 to 10, characterized in that overall a molar ratio of component A) to component B) of 1.0: 0.95 to 0.95: 1.0 is present.

13. Thermoplastic polyurethane obtainable or obtained by a process according to any one of claims 1 to 12.

14. Thermoplastic polyurethane according to claim 13, characterized in that the L * value, measured in the CIELab color space with illuminant D 65, is between 80 and 100 and the b * value is between -0.5 and 1.5, the L * value is preferably between 80 and 100 and the b * value between -0.5 and 1.0.

15. Use of a thermoplastic polyurethane according to claims 14 or 15 in a molding process with melting of the thermoplastic polyurethane, in particular for the production of components for vehicles. 16. Composition, characterized in that it contains at least one thermoplastic

Polyurethane polymer according to one of claims 13 or 14 and at least one additive and / or another thermoplastic polymer.

17. Thermoplastic molding compound, characterized in that it comprises at least one composition according to Claim 16.

18. Shaped body, film and / or fiber, characterized in that the shaped body, the film or the fiber at least one thermoplastic polyurethane polymer according to one of the Claims 13 or 14, comprising at least one thermoplastic molding composition according to claim 17 or at least one composition according to claim 16.

19. Use of a thermoplastic polyurethane polymer according to one of claims 13 or 14, a thermoplastic molding composition according to claim 17 or one

Composition according to Claim 16 for the production of a shaped body, a film and / or a fiber.

Use of a thermoplastic polyurethane polymer according to one of claims 13 or 14 for the production of a composition or a thermoplastic molding material.