WO2007101807A1

WO2007101807A1 - Process for preparing prepolymers having isocyanate groups

Info

Publication number: WO2007101807A1
Application number: PCT/EP2007/051863
Authority: WO
Inventors: Frank Prissok; Rüdiger Krech
Original assignee: Basf Se
Priority date: 2006-03-06
Filing date: 2007-02-28
Publication date: 2007-09-13

Abstract

A process for continuously preparing prepolymers having isocyanate groups, characterized in that the preparation is performed in an extruder.

Description

Process for the preparation of isocyanate group-containing prepolymers

description

The invention relates to processes for the continuous preparation of prepolymers containing isocyanate groups, preferably with an NCO content of between 1% and 50%, preferably between 1% and 30%, preferably between 1% and 25%, particularly preferably between 3% and 23%, in particular between 4% and 20%, the preparation being carried out in an extruder, preferably reaction extruder, and preferably the isocyanate group-containing prepolymer being taken from the extruder. Furthermore, the invention relates to prepolymers obtainable in this way. In addition, the invention relates to processes for the preparation of compact or preferably foamed, thermoplastic or crosslinked, soft, semi-hard or hard polyurethanes, which may optionally have urea, isocyanurate, allophanate and / or biuret structures, wherein the after process according to the invention obtainable prepolymers used.

The preparation of prepolymers containing isocyanate groups and their use in polyurethane chemistry is generally known and usually takes place in a batch process. In this case, the melted isocyanate is initially taken in a vessel, heated and slowly added the required amount of polyol and / or diol with stirring. Depending on the recipe, the reaction mixture is then heated or only stirred. After the reaction has subsided, the NCO content of the reaction product and, if necessary, the viscosity are determined to control the conversion. If the measured NCO value corresponds to that calculated for the reaction, the batch can be cooled and vented. Usual production times of an approach are between 2 and 6 hours, the batch sizes can be between 10 kg and 10 t. The size of the batch increases the risk of a "Durchgehreaktion", in which the heat removal at large batch volume is smaller than the heat of reaction generated, and in which due to side reaction at high temperatures geliert the approach and the reactor is blocked or destroyed said side reactions is the production of alikalihaltigen prepolymers or prepolymers with amine-started polyols or prepolymers containing deliberately high levels of allophanate or isocyanurate, almost impossible.

The object of the invention was to develop a process for the preparation of isocyanate group-containing prepolymers which has a high productivity and process safety and is suitable for industrial use. This should allow a high conversion and be accessible to prepolymers that are alkaline or are produced with amine-initiated polyols. Also prepolymers, which have a high content of allophanate or isocyanurate groups, should be able to be manufactured safely and economically with the new method. These objects have surprisingly been achieved by a process for the continuous preparation of isocyanate group-containing prepolymers, in which one carries out the preparation in an extruder, preferably reaction extruder.

As a result of the continuous process according to the invention for the preparation of isocyanate prepolymers, the reaction time customary in the boiler process can be reduced from more than 2 hours to about 90 seconds. This is on the one hand by the continuous intensive mixing of the reactants in the extruder, preferably reaction sextruder, on the other hand achieved by the very rapid material heating to temperatures that are not applicable in the boiler process. The extremely rapid material heating in this continuous process is due to the very large surface / volume ratio of the reaction extruder, the intensive mixing with high shear rates and the additional mechanically introduced and converted into heat energy. The targeted cooling and heating of the lateral surfaces can be traversed in the reaction extruder temperature / time profiles that are not displayed in a boiler system. Thus, the product can be heated to 180 ° C within 90 seconds, reacted and cooled to 60 ° C to prevent side reactions and is surprisingly reacted after about 90 seconds. The drastically reduced by the elevated temperatures viscosities of the starting materials and the prepolymer additionally favor the intensive mixing and a fast Abreaktion. Since the side reactions can be suppressed by the rapid expansion and the rapid cooling, the reaction can be accelerated by suitable catalysts, such as Sn, Zn, Ti, alkali or amine compounds, without the feared in the boiler process "Durchgehreaktion" entry.

With the aid of this new technology, in addition to the advantage of rapid and continuous preparation, it is also possible to prepare prepolymers which can not be prepared via a kettle process, for example prepolymers with fillers, basic prepolymers or catalyzed prepolymers. Prepolymers of highly reactive components could not be produced in the usual quality in stirred tanks with a volume of 1 to 30 m ³ due to the structurally limited heat dissipation.

Preferred design features, which may also be implemented individually, are, for example:

Pre-tempered storage containers for isocyanate (a), polyol (b), chain extender (c) Premix of isocyanate-reactive components (b) and optionally (c)

• Temperature control of the raw material streams via plate heat exchangers • High screw speed for intensive mixing of the reaction components since, unlike thermoplastics, a very low-viscosity product is produced

• Filling degree / reaction degree control in the reaction extruder through a gear / melt pump

• Product removal directly behind the gear pump, if necessary via a plate cooler to prevent further reaction if necessary

The preparation of prepolymers containing isocyanate groups is well known and is usually based on the reaction of (a) isocyanate with (b) isocyanate-reactive compounds. These starting materials (a) isocyanate and (b) compounds which are reactive towards isocyanates are preferably introduced into the extruder and reacted in the extruder. The preparation of the prepolymers is preferably based on the reaction of (a) isocyanate with (b) isocyanate-reactive compounds and (c) chain extenders and / or crosslinkers in the presence of (d) catalysts and optionally (e) auxiliaries. Preference is given to introducing components (b), (c), (d) and optionally (e) as a mixture into the extruder. However, it is also possible to prepare multistage block prepolymers, preferably by metering the prepolymer raw materials into different reaction zones of the extruder. This is preferably carried out in such a way that, for example, in the first zone, an isocyanate is reacted with a less reactive polyether diol and in the 3 zone a reactive chain extender is introduced into the reaction extruder with the aid of which a short-chain block structure is built up. It is also possible to pre-mix two reaction components directly before the entry into the reaction extruder in a tube or mixing head, to react in the first extruder zone and to allow the resulting product to form a block structure with further raw materials which are introduced into the extruder in the subsequent zones , Furthermore, there is the possibility of optionally formed gas, volatile components or unreacted monomers in a non-pressurized zone of the extruder, which is achieved by a suitable screw combination, to remove from the reaction mixture before a further reaction is to take place. By applying a vacuum in the non-pressurized zone, the degassing and purification of the reaction mixture can be further improved. Furthermore, a cascade of extruders can be used to obtain an improved block structure of the prepolymers, if the length of the extruder used for the individual production steps is not sufficient and multi-stage reactions are carried out in which eg degassing are required to reaction equilibriums in the desired direction move. A dosage of reaction quenchers, which prevent an undesired further reaction of the mixture, can preferably take place after the melt pump. Particularly preferred is the following structure:

Premix of the less reactive polyols with the isocyanate and optionally catalysts, entry of the premix in the first zone of the extruder, metering the more reactive chain extender in the second zone of the extruder, degassing in the fourth zone of the extruder, melt pump for pressure and flow control, dosing for reaction quenchers, heat exchangers for cooling the reaction mixture. Accordingly, processes for the continuous preparation of isocyanate group-containing prepolymers in an extruder are also particularly preferred, the preparation being based on the reaction of (a) isocyanate with (b) isocyanate-reactive compounds and (c) chain extenders and / or crosslinkers, if appropriate in the presence of (d) catalysts, wherein the isocyanate-reactive compounds (b) are premixed with the isocyanate (a) and optionally catalysts (d) in the first zone of the extruder, the chain extenders and / or crosslinking agents (c) in the second zone of the extruder added to the reaction mixture, and wherein the extruder degassing in the fourth zone of the extruder, melt pump for pressure and flow control, dosing possibility for reaction quencher and heat exchanger for cooling the reaction mixture.

In the extruder process according to the invention, the synthesis components (a), (b) and optionally (c), (d) and / or (e) can be introduced into the extruder individually or as a mixture and reacted. The prepolymer obtainable according to the invention has free isocyanate groups, preferably in the amount described in the introduction. Accordingly, the amounts of isocyanate used and isocyanate-reactive compounds are selected. Mixing ratios to achieve a certain NCO content to choose and calculate the skilled person is generally familiar.

The starting components for the preparation of the prepolymers are presented later. A particular advantage in the present process according to the invention consists in using, as isocyanate-reactive compounds, those which contain an increased alkali content or amine groups or which can use amine-initiated polyols, for example those based on ethylenediamine, which are commercially available. Prepolymer have an autocatalytic effect. In addition, additives can be used directly in the prepolymer formation, which exhibit a catalytic effect on the polyurethane reaction, such as organic metal compounds, tin dioctoate, zinc acetylacetonate, titanic acid esters, iron, alkali metal or tertiary amine compounds, since compared to Boiler process significantly more effective heat exchange process in a reaction extruder due to the small layer thicknesses of the material flows and the constant new formation of their contact surfaces to the extruder inner wall similar to the principle of a thin-film reactor excess heat effective can dissipate full and can be effectively suppressed unwanted side reactions due to the short reaction times and rapid cooling. Accordingly, processes are also preferred in which the compounds which are reactive toward isocyanates are those which have an alkali content of> 50 ppm, based on the total weight, and / or at least one, preferably 1 to 3, amino groups, preferably tertiary and / or secondary, particularly preferably contain tertiary amino groups. Compared to the known batch production, it is now possible for the first time to use these starting components in a large-scale process for the preparation of prepolymers.

The starting materials for the preparation of the prepolymer can preferably be fed to the extruder at a temperature of between 20.degree. C. and 200.degree. C., preferably between 50.degree. And 150.degree. C., in particular between 70.degree. And 130.degree. This temperature control of the starting materials for the preparation of the prepolymer prior to feeding into the extruder can be preferably by means of plate heat exchangers, e.g. Type 30.61 OH.108.1 1. of manufacturer Pressko AG. carry out.

Extruders which can be used are generally known and commercially available extruders. Suitable extruders are e.g. known as reaction extruder for the production of thermoplastic polyurethane. Suitable extruders are, for example, those which are commercially available from Coperion Werner & Pfleiderer under the name ZSK twin-screw kneader.

Preference is given to using a twin-screw extruder. As twin-screw twin-screw extruders it is possible to use the known and commercially available machines. Preference is given to machines whose two shafts rotate in the same direction. The screw clearance, that is to say the distance between the screw comb and the inner wall of the extruder housing, is preferably between 0.1 mm and 1.1 mm, particularly preferably in a range between 0.35 and 0.8 mm.

Preference is given to using self-cleaning twin-screw extruders whose diameter is in the range between 32 and 133 mm. Self-cleaning twin-screw extruders with an L / D ratio, ie a ratio of screw length to screw diameter, of at least 8 are more preferred. The length / diameter ratio is particularly preferably between 20 and 56.

Advantageously, the preferably self-cleaning twin-screw extruder has a mixing part stock of the extruder screw of 5/100 to 25/100 of the entire length of the extruder screw.

Particularly suitable are, for example, twin-screw extruder type .ZSK Fa. Coperion Werner & Pfleiderer, Stuttgart. Further particularly preferred embodiments are co-rotating twin-screw extruder with close-meshed, self-cleaning screw profiles according to Erdmengerprinzip with screw diameters of 58 to 19 19 mm and a UD ratio of 20 to 56.

The reaction in the extruder is preferably carried out at a temperature between 20 ° C and 250 ° C, preferably between 50 and 200 ° C, in particular between 80 and 160 ° C. In this case, over the length of the extruder, a temperature profile can be set, which is adjusted according to the process task both downstream rising (at high viscosities) and falling (for highly exothermic processes).

The screw speed is preferably between 50 and 2000 revolutions per minute, preferably between 100 and 1000.

The average residence time of the reaction mixture in the extruder is preferably less than 5 minutes, preferably less than 3 minutes.

Particular preference is given to processes in which the starting materials for the preparation of the prepolymer are fed to the extruder at a temperature between 20.degree. C. and 200.degree. C., the reaction is carried out in the extruder at a temperature between 20.degree. C. and 250.degree. C., the residence time the reaction mixture in the extruder between 10 s and 300 s and the removal temperature is after the cooler between 20 ° C and 100 ⁰ C.

The increase in productivity compared to the boiler process is due to the much more effective heat exchange process in a reaction extruder due to the small layer thicknesses of the material streams and the constant new formation of their contact surfaces to the extruder inner wall similar to the principle of a thin-film reactor with simultaneous intensive mixing of the reactants. In the extruder process described, high-viscosity products with high output can also be processed, since the extruder is sufficiently mechanically stable and has a self-cleaning effect via the screw guide. Excess heat can be removed or supplied much more effectively than in a reactor due to the large contact area. Owing to the short reaction times and the rapid cooling, undesirable secondary reactions are effectively suppressed, but by the choice of suitable catalysts and temperatures, on the other hand, reactions which would lead to a "through reaction" in large volumes, as in a boiler, can take place preferentially.

In the extrusion process according to the invention, in which the raw materials can also be premixed in a mixing head, for example, the reaction mixture is intensively the highly effective heat exchange mixed. In addition, mechanical energy in the form of shear is introduced into the product via the screws. In contrast to a simple reaction tube with laminar product flow, the reaction extruder also works under the conditions of forced conveyance as a result of the screw rotation. Depending on the process objective one can influence the mixing, dicing, conveying and Rückförderverhalten in the screw reactor by selecting the screw elements, whereby, for example, the Schneckenfüllgrad increased, the mixing intensity improved and the residence time can be increased. Suitable screw elements to increase the residence time are promoting neutral elements and those with oppositely directed in-house promotion. Detailed information on this can be found in the brochure literature of the manufacturer Coperion Werner & Pfleiderer - "Twin-screw worm kneaders ZSK - Worth knowing about development and process engineering." Furthermore, one can work in the extruder with high viscosities, since the product, ie the prepolymer in the reaction extruder, may react and moreover by the self-cleaning screws, the risk of clogging of the reaction extruder is low.

In a preferred embodiment, a gear pump may be arranged at the end of the extruder, whose operation is based on the well-known and described in the technical literature pumping fluid handling according to the principle of a positive displacement pump by rotating, interlocking Zahräder. The delivery rates depend on gear speed, free Zahradvolumen, differential pressure, material viscosity and gear bearing gap dimensions. The gear pump is speed-controlled for the said application for maintaining a certain form.

With the aid of this preferred gear pump at the end of the extruder, it is possible to keep the degree of filling of the extruder constant by means of the admission pressure control, and thus preferably to ensure a constant reaction time for the reaction mixture. Preference is given to the prepolymer behind the gear pump, which is connected downstream of the extruder screw, and preferably by means of a plate heat exchanger to a storage temperature of 20 to 60 ° C cool. Thus, it is particularly preferred that the prepolymer after removal from the extruder by means of a plate cooler to a temperature between 20 ° C and 100 ° C, preferably cool between 30 and 80 ⁰ C.

In a further preferred embodiment, it is possible by means of vacuum degassing of the extruder, preferably in the last reaction zones, to remove volatile components such as monomers, auxiliaries or solvents from the prepolymer. This preferred embodiment makes it possible to produce products having low monomer content without the need for an additional process step, for example distillation. The degassing of a polymer melt or a prepolymer, ie the removal of volatile components these are generally made from decompressively constructed screw element regions which are partially filled and can be located above as well as below a degassing opening. By selecting suitable screw elements, such as, for example, elements with a high pitch, such a decompressive screw zone can be set up (sa cited company publication).

The inventive method also offers the possibility to supply solids by means of powder dosing of the reaction mixture in the extruder. Due to the intensive mixing in the extruder these fillers or solid reactants are homogeneously incorporated into the prepolymer even if due to strong density or polarity differences, the incorporation in a boiler reactor is not completely possible. Products which are solid at the reaction temperature are both comminuted and homogeneously dispersed by the combination of shear and pressure.

The process according to the invention is preferably a technical, particularly preferably large-scale process. Thus, a method is preferred in which one produces more than 1000 kg / h of the prepolymer with an extruder.

As indicated initially, an advantage of the process is that it makes it possible to obtain prepolymers which have isocyanurate structures. Preference is furthermore given to processes with which a prepolymer is prepared which has allophanate structures.

The prepolymers obtainable according to the invention may preferably have an alkali content of> 50 ppm. Such prepolymers have hitherto not been industrially available, because in industrial boilers alkali contents> 10 ppm can only be processed under critical conditions and products with an alkali content> 50 ppm can no longer be produced.

The prepolymers obtainable according to the invention can be continuously removed from the extruder via a plate heat exchanger or a tube cooler and stored or immediately further processed. The prepolymers according to the invention can be used for the generally known preparation of polyurethanes which may optionally contain urea, isocyanurate and / or biuret structures. They may be compact or foamed polyurethanes, e.g. Polyurethane soft, semi-hard or rigid foams. However, corresponding prepolymers are also suitable for the production of microcellular polyurethane elastomers or thermoplastic polyurethane elastomers.

In the following, the starting components for the preparation of the prepolymers are exemplified. The components (a), (b) and optionally (c), (d) and / or (e) usually used in the preparation of the prepolymers are described below by way of example: a) As organic isocyanates (a) it is possible to use generally known aliphatic, cycloaliphatic, araliphatic and / or aromatic isocyanates, for example tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, Methyl pentamethylene diisocyanate 1, 5, 2-ethyl butylene diisocyanate

1, 4, pentamethylene diisocyanate-1, 5, butylene diisocyanate 1, 4, 1-isocyanato SSδ-trimethyl-δ-isocyanato-methyl-cyclohexane (isophorone diisocyanate, IPDI), 1, 4- and / or 1, 3-bis (isocyanatomethyl) cyclohexane (HXDI), 1,4-cyclohexane diisocyanate, 1-methyl-2,4- and / or -2,6-cyclohexane diisocyanate and / or 4,4 ' , 2,4'- and 2,2'-dicyclohexylmethane diisocyanate, 2,2'-, 2,4'- and / or 4,4'-

Diphenylmethane diisocyanate (MDI), 1, 5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-toluene diisocyanate (TDI), diphenylmethane diisocyanate, 3,3'-dimethyl-diphenyl-diisocyanate, 1, 2-diphenylethane-diisocyanate and / or phenylene diisocyanate and / or polyisocyanates such as Polyphenylpolymethylenepolyiso- cyanate. The isocyanates may be in the form of the pure compound, in mixtures and / or in modified form, for example in the form of uretdiones, isocyanurates, allophanates or biurets, or in the form of urethane and isocyanate groups containing reaction products, so-called isocyanate prepolymers, be used.

b) As isocyanate-reactive compounds (b) it is possible to use the generally known isocyanate-reactive compounds, for example polyesterols, polyetherols and / or polycarbonate diols, which are usually also grouped under the term "polyols", with molecular weights of from 500 to 8,000 , preferably 600 to 6000, especially 800 to

4000, and in elastomer applications preferably have an average functionality of from 1.8 to 2.2, more preferably from 1.9 to 2.1. For products for other applications, the functionality is usually between 1 and 6, with 2 to 4 preferred for soft foam applications and 3 to 6 for rigid foam applications.

c) As chain extenders and / or crosslinkers (c) it is possible to use generally known aliphatic, araliphatic, aromatic and / or cycloaliphatic compounds having a molecular weight of 50 to 499 g / mol, preferably 62 g / mol to 499 g / mol, for example selected from the group of di- and / or trifunctional alcohols, di- to tetrafunctional polyoxyalkylene polyols and alkyl-substituted aromatic diamines or of mixtures of at least two of said chain extenders and / or crosslinking agents. As (c), for example, alkanediols having 2 to 12, preferably 2, 4, or 6 carbon atoms can be used, e.g. Ethane, 1, 3-propane, 1, 5

Pentane, 1, 6-hexane, 1, 7-heptane, 1, 8-octane, 1, 9-nonane, 1, 10-decanediol and preferably 1, 4-butanediol, dialkylene glycols having 4 to 8 carbon atoms , as for example, diethylene glycol and dipropylene glycol and / or di- to tetrafunctional polyoxyalkylene-polyols. However, branched-chain and / or unsaturated alkanediols having usually not more than 12 carbon atoms, such as, for example, 1,2-propanediol, 2-methyl-, 2,2-dimethyl-1,3-propanediol, 2,2-butyl-2-ethylpropanediol, are also suitable 1, 3, butene-2-diol-1, 4 and butyne-2-diol-1, 4, diesters of terephthalic acid with glycols having 2 to 4 carbon atoms, such as terephthalic acid-bis-ethylene glycol or butanediol-1, 4, hydroxyalkylene ethers of hydroquinone or resorcinol, such as, for example, 1, 4-di (b-hydroxyethyl) hydroquinone or 1, 3-di (b-hydroxyethyl) -resorcinol, alkanolamines having 2 to 12 carbon atoms, such as ethanolamine, 2-aminopropanol and 3-amino-2,2-dimethylpropanol, N-alkyl-dialkanolamines, such as N-methyl and N-ethyl-diethanolamine. Examples of higher-functionality crosslinking agents (c) which may be mentioned are trifunctional and higher-functional alcohols, for example glycerol, trimethylolpropane, pentaerythritol and trihydroxycyclohexyls, and trialkanolamines, for example triethanolamine. Alkali-substituted aromatic polyamines having molecular weights preferably from 122 to 400, in particular primary aromatic diamines which have at least one alkyl substituent in the ortho position relative to the amino groups, which have the reactivity of the amino group owing to steric hindrance, have proven to be particularly suitable as chain extenders which are liquid at room temperature and at least partially, but preferably completely, miscible with the higher molecular weight, preferably at least difunctional compounds (b) under the processing conditions. To prepare the prepolymers, the industrially readily available 1, 3,5-triethyl-2,4-phenylenediamine, 1-methyl-3,5-diethyl-2,4-phenylenediamine, mixtures of 1-methyl-3,5 diethyl-2,4- and -2,6-phenylenediamines, so-called

DETDA, isomer mixtures of 3,3'-di- or 3,3 ', 5,5'-tetraalkyl-substituted 4,4'-diaminodiphenylmethanes having 1 to 4 carbon atoms in the alkyl radical, in particular methyl, ethyl and isopropyl radicals bound 3 containing , 3 ', 5,5'-tetraalkyl-substituted 4,4'-diamino-diphenylmethanes and mixtures of said tetraalkyl-substituted 4,4'-diamino-diphenylmethanes and DETDA can be used. To achieve special mechanical properties, it may also be expedient to use the alkyl-substituted aromatic polyamines in admixture with the abovementioned low molecular weight polyhydric alcohols, preferably dihydric and / or trihydric alcohols or dialkylene glycols.

To accelerate the reaction, generally known catalysts (d) can be added to the reaction batch in the preparation of the prepolymer. The catalysts (e) can be added individually as well as in admixture with each other. Suitable catalysts which, in particular, see the reaction between the NCO groups of the diisocyanates (a) and the hydroxyl groups of

Accelerating structural components (b) and (c) are the organometallic compounds known and customary in the prior art, such as tin (II) -, Tin (IV), titanium (IV) or zinc (II) compounds of organic carboxylic acids, e.g. Tin (II) dioctoate, tin (II) dilaurate, dibutyltin diacetate, dibutyltin dilaurate, di-n-octyltin (IV) bis (2-ethylhexyl thioglycolate) and n-octyltin (IV) tris (2 ethylhexyl thioglycolate) and tertiary amines such as tetramethylethylenediamine, N-methylmorpholine, diethylbenzylamine, triethylamine, dimethylcyclohexylamine, diazabicyclooctane, N, N'-dimethylpiperazine, N-methyl, N '- (4-N-dimethylamino) -butylpiperazine, N, N, N ', N ", N" -pentamethyldiethylenediamine or the like. Also suitable as catalysts are amidines, for example 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tris (dialkylaminoalkyl) -s-hexahydrotriazines, in particular tris- (N, N-dimethylaminopropyl) - s-hexahydrotriazine, tetraalkylammonium hydroxides, such as, for example, tetramethylammonium hydroxide, alkali metal hydroxides, such as, for example, sodium hydroxide, and alkali metal alkoxides, such as, for example, sodium methylate and potassium isopropylate, and alkali metal salts of long-chain fatty acids having 10 to 20 carbon atoms and optionally pendant OH groups. The catalysts are usually used in amounts of 0.0001 to 0.1 parts by weight per 100 parts by weight.

Parts of polyhydroxyl compound (b) used.

Auxiliaries (e) can be used in the preparation of the prepolymers according to the invention. These include, for example, well-known surface-active substances, foam stabilizers, cell regulators, fillers, flame retardants, nucleating agents, antioxidants, stabilizers, lubricants and mold release agents, dyes and pigments. As surface-active substances are e.g. Compounds which serve to assist the homogenization of the starting materials and, if appropriate, are also suitable for regulating the cell structure. Mention may be made, for example, of emulsifiers, e.g. the sodium salts of castor oil sulfates or of fatty acids and salts of fatty acids with amines, e.g. diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleic acid, salts of sulfonic acids, e.g. Alkali or ammonium salts of dodecylbenzene or dinaphthylmethanedisulfonic acid and ricinoleic acid; Foam stabilizers, such as siloxane-oxalkylene copolymers and other organosiloxanes, oxyethylated alkylphenols, oxyethylated fatty alcohols, paraffin oils, castor oil or ricinoleic acid esters, Turkish red oil and peanut oil and cell regulators, such as paraffins, fatty alcohols and dimethylpolysiloxanes. To improve the emulsifying action, the cell structure and / or their stabilization, oligomeric polyacrylates having polyoxyalkylene and fluoroalkane radicals as side groups are also suitable.

Fillers, in particular reinforcing fillers, are the conventional, customary organic and inorganic fillers, reinforcing agents and weighting agents. Specific examples are: inorganic fillers such as silicate minerals, for example phyllosilicates such as antigorite, serpentine, hornblende, amphibole, chrysotile, talc; Metal oxides, such as kaolin, aluminum oxides, aluminum silicate, titanium oxides and iron oxides, metal salts such as chalk, barite and inorganic pigments such as cadmium sulfide, zinc sulfide and glass particles. Suitable organic fillers are, for example: carbon black, melamine, isocyanurates, expandable graphite, rosin, cyclopentadienyl resins and graft polymers. As reinforcing fillers preferably find use fibers, such as carbon fibers or glass fibers, especially when a high heat resistance or very high stiffness is required, the fibers may be equipped with adhesion promoters and / or sizing. The inorganic and organic fillers may be used singly or as mixtures and are incorporated in the prepolymer usually in amounts of 0.5 to 50% by weight, preferably 1 to 20% by weight, based on the total weight of the prepolymer.

Suitable flame retardants are, for example, tricresyl phosphate, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate and tetrakis. (2-chloroethyl) ethylenediphosphate. In addition to the aforementioned halogen-substituted phosphates, inorganic flame retardants such as red phosphorus, alumina hydrate, antimony trioxide, arsenic trioxide, ammonium polyphosphate, and calcium sulfate, or cyanuric acid derivatives, e.g. Melamine or mixtures of at least two

Flame retardants, e.g. Ammonium phosphates and melamine and optionally starch and / or expandable graphite are used for flameproofing.

Further information on the other common additives and auxiliaries mentioned above can be found in the technical literature.

In addition to the abovementioned components a) and b) and optionally c), d) and e) it is also possible to use chain regulators, usually having a molecular weight of from 31 to 499. Such chain regulators are compounds which have only one isocyanate-reactive functional group, such as. As monofunctional alcohols, monofunctional amines and / or monofunctional polyols. By means of such chain regulators, a flow behavior, in particular with TPUs, can be adjusted in a targeted manner. Chain regulators can generally be used in an amount of 0 to 5, preferably 0.1 to 1, parts by weight, based on 100 parts by weight of component b), and fall by definition under component c).

All molecular weights mentioned in this document have the unit [g / mol].

The invention will be illustrated by the following examples. Examples

Preparation of NCO-containing Prepolymeren

example 1

Preparation of the NCO-containing prepolymer for elastomers

57.1 parts by weight of polytetrahydrofuran (MW 1000), 14.3 parts by weight of polytetrahydrofuran (MW 2000) and 28.6 parts by weight of 4,4'-diisocyanato-diphenylmethane (Lupranat® MET from BASF Aktiengesellschaft) were heated from storage containers and downstream heat exchangers were metered into the draw-in area of a Leistritz 34mm co-rotating twin-screw reaction extruder with the L / D ratio of 1:35 running at 300 rpm. The product was taken directly after the melt pump of the plant and cooled to 80 ° C. The calculated NCO content of the reacted prepolymer is about 5.9%. The measurement inaccuracy in the NCO determination is given as + - 0.1%.

Preparation of crosslinking component:

69.2 parts by weight of 50% aqueous solution of a fatty acid sulfate

23.1 parts by weight nonionic emulsifier polyethylene glycol (PEG-40) sorbitol hexaoleate

6.5 parts by weight of silicone-based foam stabilizer (DC 193 from Dow Corning) 0.3 part by weight of di-n-octyltin bis (2-ethylhexlithioglycolate) 0.9 part by weight of a mixture of Lupragen® N 202 ( BASF Aktiengesellschaft) and

Niax® catalyst E-A-1 (GE Silicones), catalysts

are mixed with constant stirring.

Exemplary production of cylindrical shaped bodies 100 parts by weight of the prepared at 140 ° C prepolymer of variant B were mixed with 3.2 parts by weight of the crosslinking component according to using a low-pressure casting machine at 80 ° C prepolymer and 35 ° C crosslinking temperature. 73 g of the mixture were introduced into a closed at 75 ° C, sealable mold and the foam cured at 75 ° C for 15 min. In addition, block shapes were foamed. After demolding of the microcellular product, the molding was thermally postcured at 1 10 ° C for 14 h.

Example 2

Preparation of a Multifunctional NCO-Containing Prepolymer

38.7 parts by weight of a glycerol-started PO / EO polyetherol (MW 4350, F = 2.7, Lupranol® 2095 BASF Aktiengesellschaft) 9.2 parts by weight of polypropylene glycol

(MW 450, F = 2, Lupranol® 1200 from BASF Aktiengesellschaft) 5.6 parts by weight of partially carbodiimidated diisocyanato-diphenylmethane (Lupranat® MM 103 from BASF Aktiengesellschaft) 46.5 parts by weight of 4,4'-diisocyanato-diphenylmethane ( Lupranat® MET of BASF Aktiengesellschaft)

were metered from heated storage tanks and downstream heat exchangers in the catchment area of a Coperion Werner & Pfleiderer 92mm co-rotating twin-screw reaction extruder with the L / D ratio of 1:48, which ran at 180 revolutions per minute. The product was taken directly after the melt pump of the plant and cooled to 50 ° C. The calculated NCO content of the reacted prepolymer is about 14.5%. The measurement inaccuracy in the NCO determination is given as + - 0.1%.

Example 3

Preparation of an autocatalytic NCO-containing prepolymer

30.0 parts by weight of polypropylene glycol

(MW 1100, F = 2, Lupranol® 1 100 from BASF Aktiengesellschaft) 15.5 parts by weight of an ethylenediamine-initiated PO / EO polyetherol (MW 3800, F = 4, Lupranol® 2001 from BASF Aktiengesellschaft) 54.5 parts by wt. 4,4 '/ 2,4 diisocyanato-diphenylmethane (Lupranat® MIS BASF Aktiengesellschaft)

were metered from heated storage tanks and downstream heat exchangers in the catchment area of a Coperion Werner & Pfleiderer 58mm co-rotating twin-screw reaction extruder with the L / D ratio of 1:48, which ran at 200 revolutions per minute. The product was taken directly after the melt pump of the plant and cooled to 50 ° C. The calculated NCO content of the reacted prepolymer is about 14.9%. The measurement inaccuracy in the NCO determination is given as + - 0.1%.

Example 4

Preparation of a low-NCO-prepolymer

87.5 parts by wt. Of a glycerol-started PO / EO polyetherol (MW 4350, F = 2.7, Lupranol® 2095 from BASF Aktiengesellschaft) 12.5 parts by wt. 2,4 diisocyanato-diphenylmethane (Lupranat® MCI from BASF Aktiengesellschaft )

were metered from heated storage tanks and downstream heat exchangers in the catchment area of a Coperion Werner & Pfleiderer 58mm co-rotating twin-screw reaction extruder with the L / D ratio of 1:48, which ran at 200 revolutions per minute. The product was taken directly after the melt pump of the system and cooled to 60 ⁰ C. The calculated NCO content of the reacted prepolymer is about 1.7%. The measurement inaccuracy in the NCO determination is given as + - 0.1%.

Comparative Example 1

1. Preparation of the NCO-containing Prepolymeren

57.0 parts by weight of polytetrahydrofuran 2000 (PolyTHF 2000 from BASF Aktiengesellschaft) and 14.3 parts by weight of polytetrahydrofuran 1000 (polyTHF 1000 from BASF Aktiengesellschaft) and 0.2 part by weight of foam stabilizer based on silicone (DC 193 from Dow Corning) were metered in a reactor (10 minutes), heated under nitrogen atmosphere within 30 minutes at 140 ⁰ C and stirring with 28.5 parts by weight of 4,4'-diisocyanato-diphenylmethane (Lupranat® MET BASF Aktiengesellschaft) added. The reaction temperature was kept at 145 ° C for 10 min to complete the reaction and to build allophanate and then cooled to 90 ⁰ C within 90 minutes and drained. This resulted in an almost colorless liquid with an NCO content of 5.9% and an apparent Allopha- natgehalt of 0.2%. The production time was 150 minutes.

2. Preparation of Crosslinking Component:

74.1 parts by weight of 50% aqueous solution of a fatty acid sulfate 24.6 parts by weight of nonionic emulsifier polyethylene glycol (PEG-40) sorbitol hexa-oleate

0.4 parts by weight of di-n-octyltin bis (2-ethylhexlthioglycolat) 0.9 parts by weight of a mixture of Lupragen® N 202 (BASF Aktiengesellschaft) and

Niax® catalyst E-A-1 (GE Silicones), catalysts

3. Production of the cylindrical shaped body

100 parts by weight of the prepolymer according to (1) were mixed with 3.03 wt. Parts by the crosslinking component according to (2) by means of a low pressure at 80 ⁰ C Prepo- lymer- and 35 ° C. crosslinking agent, 62 g of the mixture in introduced a closed at 75 ° C, sealable mold and the foam cured at 75 ° C for 15 min. In addition, block shapes were foamed. After demolding of the microcellular product, the molding was thermally postcured at 1 10 ° C for 14 h.

Claims

claims

1. A process for the continuous preparation of isocyanate group-containing prepolymers, characterized in that one carries out the preparation in an extruder.

2. The method according to claim 1, characterized in that the prepolymer has an NCO content between 1% and 50%.

3. The method according to claim 1, characterized in that the preparation is based on the reaction of (a) isocyanate with (b) isocyanate-reactive compounds.

4. The process as claimed in claim 1, wherein the preparation is based on the reaction of (a) isocyanate with (b) isocyanate-reactive compounds and (c) chain extenders and / or crosslinkers in the presence of (d) catalysts and optionally (e) excipients.

5. The method according to claim 4, characterized in that the components (b), (c), (d) and optionally (e) are introduced as a mixture in the extruder.

6. The method according to claim 1, characterized in that one produces multi-stage block prepolymers.

7. The method according to claim 3, characterized in that one uses as isocyanate-reactive compounds which contain an alkali content> 50 ppm and / or at least one amino groups.

8. The method according to claim 1, characterized in that feeding the starting materials for the production of the prepolymer at a temperature between 20 ° C and 200 ° C to the extruder.

9. The method according to claim 1, characterized in that the starting materials for the preparation of the prepolymer with a temperature between 20 ° C and

200 ° C fed to the extruder, the reaction is carried out in the extruder at a temperature between 20 ° C and 250 ° C, the residence time of the reaction mixture in the extruder between 10 s and 300 s and the removal temperature after the cooler between 20 ° C and 100 ° C is.

10. The method according to claim 8, characterized in that tempered the starting materials for the preparation of the prepolymer before being fed into the extruder by means of plate heat exchanger.

1 1. The method according to claim 1, characterized in that one uses a twin-screw extruder.

12. The method according to claim 1, characterized in that one carries out the reaction in the extruder at a temperature between 20 ° C and 250 ° C.

13. The method according to claim 1, characterized in that the screw speed is between 50 and 2000 revolutions per minute.

14. The method according to claim 1, characterized in that the average residence time of the reaction mixture in the extruder is less than 5 minutes.

15. The method according to claim 1, characterized in that one holds by means of a gear pump at the end of the extruder, the degree of filling of the extruder via a form control constant.

16. The method according to claim 1, characterized in that one removes the prepolymer behind a gear pump, which is connected downstream of the extruder screw.

17. The method according to claim 1, characterized in that one cools the prepolymer after removal from the extruder by means of a plate cooler to a temperature between 20 ° C and 100 ° C.

18. The method according to claim 1, characterized in that by means of vacuum degassing of the extruder volatile components removed from the prepolymer.

19. The method according to claim 1, characterized in that feeding solids by means of powder dosing of the reaction mixture in the extruder.

20. The method according to claim 1, characterized in that one produces more than 1000 kg / h of the prepolymer with an extruder.

21. The method according to claim 1, characterized in that the prepolymer has isocyanurate structures.

22. The method according to claim 1, characterized in that the prepolymer has allophanate structures.

23. The method according to claim 1, characterized in that the prepolymer has an alkali content of> 50 ppm.

24. The method according to claim 1, characterized in that the preparation is based on the reaction of (a) isocyanate with (b) isocyanate-reactive compounds and (c) chain extenders and / or crosslinking agents optionally in the presence of (d) catalysts, wherein the isocyanate-reactive compounds (b) are premixed with the isocyanate (a) and, if appropriate, catalysts (d) in the first zone of the extruder, the chain extenders and / or crosslinkers (c) in the second zone of the extruder to the reaction mixture metered in, and wherein the extruder degassing in the fourth zone of the extruder, melt pump for pressure and flow control, dosing option for reaction quencher and heat exchanger for cooling the reaction mixture.

25. Prepolymers obtainable by a process according to one of claims 1 to 24.

26. Process for the preparation of polyurethanes, characterized in that one uses prepolymers obtainable according to one of claims 1 to 24.