Method for preparing isocyanurate-group-containing polyisocyanates

Abstract

The invention relates to a method for preparing isocyanurate-group-containing polyisocyanates P by trimerising • A) at least one organic di- or polyisocyanate with isocyanate groups bound aliphatically, cycloaliphatically and / or araliphatically independently of one another in the presence of • B) at least one trimerisation catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted quaternary ammonium hydroxides of the choline type and • C) at least one alcohol as solvent.

Description

[0001] Process for the preparation of polyisocyanates containing isocyanurate groups

[0002] The production of polyisocyanates containing isocyanurate groups by trimerization of monomeric di- and / or polyisocyanates has long been known.

[0003] Typically, trimerization catalysts are used, such as quaternary tetraalkyl or trialkylarylammonium hydroxides, such as Triton-B and hydroxyalkyl-substituted quaternary ammonium hydroxides of the choline type, e.g. choline acetate.

[0004] The known prior art processes (e.g., EP 2 700 665 A1) are conducted in such a way that an alcoholic solution of the catalyst is first added to the isocyanate component to be trimerized. The resulting initiation of the exothermic reaction causes the temperature of the reaction mixture to rise. The exothermic reaction is controlled throughout the further course of the process by adding adjusted amounts of the catalyst solution.

[0005] It has now been surprisingly discovered that the reaction behavior can be improved if, after the start of the reaction by initially adding an alcoholic catalyst solution, only alcohol is added, but no further catalyst. This dosing behavior leads to less catalyst being consumed for a constant reaction time, or, for a constant catalyst quantity, the reaction time can be shortened by a faster reaction start for semi-batch processes, and the throughput for cascade processes can be increased. In the first case, the lower catalyst consumption also means fewer stoppers are required to stop the reaction, and less catalyst is present in the product, which improves product quality (less tendency to discoloration). A reduced reaction time means a more economical process.In addition, the reaction process can be better adapted to the quality of the diisocyanate used (with regard to acidic components), since the amounts of catalyst and alcohol added can be controlled independently of each other.

[0006] The invention relates to a process for the preparation of polyisocyanates P containing isocyanurate groups by trimerization

[0007] A) at least one organic di- or polyisocyanate having independently aliphatically, cycloaliphatically and / or araliphatically bound isocyanate groups, in the presence

[0008] B) at least one trimerization catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted quaternary ammonium hydroxides of the choline type and

[0009] C) at least one alcohol as solvent, comprising or consisting of the following steps

[0010] I) Placing component A in a reactor,

[0011] II) Adding the total amount of catalyst component B, as well as a first portion of component C (CTI), and trimerizing component A until a degree of trimerization T is obtained g in the range of > 0.5 to < 25%, preferably > 0.5 to < 20%, where

[0012] T g = (NCOo - NCOt) / NCOo, where

[0013] NCOo corresponds to the amount of free NCO groups originally present in the component A and

[0014] NCOt corresponds to the amount of free NCO groups in the reaction solution at time t, determined by NCO titration according to M105-ISO 11909,

[0015] III) Adding a second portion of component C (CT2) while continuing the trimerization of component A.

[0016] The above method is hereinafter referred to as Embodiment 1.

[0017] It is also possible to initially add the alcoholic catalyst solution in a high concentration and then add catalyst solution at a lower concentration after the start of the reaction.

[0018] The invention therefore also relates to a process for the preparation of polyisocyanates P' containing isocyanurate groups by trimerization

[0019] A') at least one organic di- or polyisocyanate having independently aliphatically, cycloaliphatically and / or araliphatically bound isocyanate groups, in the presence

[0020] B') at least one trimerization catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted quaternary ammonium hydroxides of the choline type and

[0021] C') at least one alcohol as solvent, comprising or consisting of the following steps

[0022] T) Placing component A' in a reactor, IF) Feeding a first portion of catalyst component B' and a first portion of component C' (C'TI), wherein catalyst component B'TI is used in amounts of > 0.6 to < 8 wt.%, preferably > 0.8 to < 5 wt.%, particularly preferably > 0.8 to < 2 wt.%, based on the first portion of component C' (C'TI) used in step IT, and trimerization of component A' until a degree of trimerization is obtained

[0023] T g ' in the range of > 0.5 to < 25%, preferably from > 0.5 to < 20%, where

[0024] T g ' = (NCOo - NCOt) / NCOo, where

[0025] NCOo corresponds to the amount of free NCO groups originally present in the submitted component A' and

[0026] NCOt corresponds to the amount of free NCO groups in the reaction solution at time t, determined by NCO titration according to M105-ISO 11909,

[0027] IIF) Adding a second portion of the catalyst component B' (B' T 2), and a second subset of component C' (C'T2), wherein catalyst component B' T 2 in amounts of > 0 to < 0.5 wt.%, preferably > 0 to < 0.1 wt.% based on the second partial amount of component C' (C' TO) used in step IIT, with continuation of the trimerization of component A'.

[0028] This method is hereinafter referred to as Embodiment 2.

[0029] For the purposes of the present invention, aliphatic compounds are understood to mean those that contain exclusively open-chain aliphatic groups, which may be branched or unbranched. Cycloaliphatic compounds are those that contain at least one cycloaliphatic ring system. Araliphatic compounds are those that contain at least one araliphatic group.

[0030] To carry out the processes according to the invention, all organic di- or polyisocyanates with an (average) molecular weight of 154-600 g / mol and independently aliphatically, cycloaliphatically, and / or araliphatically bound isocyanate groups can be used in pure form or as any desired mixtures. Examples include: pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 2-methylpentane-1,5-diisocyanate (MPDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane (1,3- and 1,4-He-XDI), 1,3- and 1,4-bis(isocyanatomethyl)benzene (1,3- and 1,4-XDI), 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI); Isophorone diisocyanate (IPDI), bis(isocyanatomethyl)norbornane (NBDI), 4-isocyanatomethyl-l,8-octane diisocyanate (triisocyanatononane, TIN), 1,3-

[0031] Bis(isocyanatomethyl)benzene, l,3-bis(2-isocyanatopropyl-2)benzene, and bis(4(2)-isocyanatocyclohexyl)methane (H12MDI, Desmodur® W, a product of Covestro AG). It is irrelevant which process is used to produce the aforementioned (poly)isocyanates, i.e., with or without the use of phosgene.

[0032] Preferably, the at least one organic di- or polyisocyanate is selected from the group consisting of PDI, HDI, MPDI, 1,3- and 1,4-HgXDI, 1,3- and 1,4-XDI, and NBDI. HDI or a mixture of HDI with PDI, MPDI, 1,3- and 1,4-HeXDI, 1,3- and 1,4-XDI, and / or NBDI is particularly preferred.

[0033] In step I of embodiment 1, component A can be degassed under reduced pressure and, if appropriate, with the addition of heat. It is preferable to degas component A in step I. The same applies to component A' in step T of embodiment 2.

[0034] As catalyst component B or B', at least one quaternary trialkylarylammonium hydroxide and / or at least one hydroxyalkyl-substituted quaternary ammonium hydroxide of the choline type is preferably used in the processes according to the invention. Particular preference is given to using at least one benzyltrialkylammonium hydroxide and / or at least one hydroxyalkyl-substituted quaternary ammonium hydroxide of the choline type. Particular preference is given to using benzyltrimethylammonium hydroxide (Triton-B) and / or 2-hydroxyethyltrimethylammonium acetate (choline acetate).

[0035] Any aliphatic and / or cycloaliphatic alcohols, preferably aliphatic alcohols, are preferably used as solvent components C or C', with low-molecular-weight mono- or diols being preferred. Examples include: methanol, ethanol, isopropanol, n-butanol, 2-ethylhexanol, 2-ethylhexane-1,3-diol, 1,2-dihydroxyethane, 1,2-dihydroxypropane, 1,3- and 1,4-dihydroxybutane, 1,6- and 2,5-dihydroxyhexane, or 2,2,4-trimethyl-1,3-dihydroxypentane, or any mixtures of these alcohols. Alcohols with at least one primary alcohol group are particularly preferred. Very particular preference is given to n-butanol, 2-ethylhexanol, 2-ethylhexane-1,3-diol, 1,2-dihydroxyethane, 1,2-dihydroxypropane, 1,3- and 1,4-dihydroxybutane, 1,6-dihydroxyhexane, or 2,2,4-trimethyl-1,3-dihydroxypentane or any mixtures of these alcohols.In embodiment 1, the at least one alcohol C used in step II may be identical to or different from the at least one alcohol used in step III. Likewise, in embodiment 2, the at least one alcohol C' used in step IIT may be identical to or different from the at least one alcohol used in step IIT.

[0036] Embodiment 1:

[0037] In step II, the total amount of catalyst component B and a first portion of the solvent component C (CTI) are fed to the reactor and component A is heated to a degree of trimerization T g in the range of > 0.5 to < 25%, preferably > 0.5 to < 20%, trimerized.

[0038] The addition of components B and C is preferably carried out in such a way that at least a portion of the total amount of catalyst component B is dissolved in at least a portion of the first portion of solvent component C. The following embodiments are preferred:

[0039] The total amount of component B is fed to the reactor dissolved in the entire first portion of component C (embodiment a), whereby the feeding can be carried out continuously or discontinuously.

[0040] The total amount of component B is fed to the reactor dissolved in a first portion of the first portion of component C, and the remaining portion of the first portion of component C is fed to the reactor as pure component C (embodiment b). Both can be carried out independently of one another continuously or discontinuously. The term "pure component C" in this context means that component C does not contain any catalysts of component B.

[0041] The catalyst component B is used in amounts of preferably > 0.3 to < 8 wt.%, particularly preferably > 0.5 to < 5 wt.%, very particularly preferably > 0.8 to < 2 wt.%, in each case based on the total amount of solvent component C used in step II, ie based on CTI.

[0042] The catalyst component B is generally used in amounts of > 0.001 to < 2 wt.%, preferably > 0.001 to < 1 wt.% and particularly preferably > 0.001 to < 0.2 wt.%, in each case based on the amount of the isocyanate component A used.

[0043] Step II can be conducted such that the trimerization starts during or after the addition of component B. This can be influenced thermally. The former option is preferred. The trimerization in step II is carried out at reaction temperatures of preferably > 50 to < 120 °C, particularly preferably > 55 to < 90 °C. If HDI is used as component A, the trimerization in step II is most preferably carried out at > 57 to < 65 °C.

[0044] In step III, a second portion of solvent component C (CT2) is added to the reactor. This can be done continuously or discontinuously.

[0045] The total amount of solvent component C added corresponds to the sum of the two partial amounts from steps II and III (CT1 + CT2). The total amount of solvent component C added is preferably > 0.3 to < 5 wt. %, particularly preferably > 1 to < 2 wt. %, based in each case on the amount of isocyanate component A used.

[0046] The trimerization in step III is carried out at reaction temperatures of preferably > 50 to < 120 °C, particularly preferably > 55 to < 90 °C. If HDI is used as component A, the trimerization in step II is very particularly preferably carried out at > 60 to < 65 °C.

[0047] The reaction temperatures in step II and step III may be the same or different.

[0048] In step III, the trimerization of component A is continued until the desired degree of trimerization is reached.

[0049] Embodiment 2:

[0050] In step IT, a first portion of the catalyst component B' (B'TI) and a first portion of the solvent component C' (C'TI) are fed to the reactor and component A' is added until a degree of trimerization T g ' in the range of > 0.5 to < 25%, preferably > 0.5 to < 20%, trimerized.

[0051] The addition of components B' and C' is preferably carried out in such a way that at least a portion of the first portion of catalyst component B' is dissolved in at least a portion of the first portion of solvent component C'. The following embodiments are preferred:

[0052] The entire first portion of component B' is fed to the reactor dissolved in the entire first portion of component C' (embodiment a'), wherein the feeding can be carried out continuously or discontinuously.

[0053] The entire first portion of component B' is fed to the reactor dissolved in a first portion of the first portion of component C', and the remaining portion of the first portion of component C' is fed to the reactor as pure component C' (embodiment b'), whereby both can be carried out independently of one another continuously or discontinuously. The term "pure component C'" in this context means that C' does not contain any catalysts of component B'.

[0054] B'TI is used in amounts of > 0.6 to < 8 wt.%, preferably > 0.8 to < 5 wt.%, particularly preferably > 0.8 to < 2 wt.%, based on the total first portion of component C' used in step IT (ie based on the total amount of C'TI).

[0055] Step IT can be conducted such that trimerization begins either during or after the addition of component B'. This can be influenced thermally. The former option is preferred.

[0056] The trimerization in step IT is carried out at reaction temperatures of preferably > 50 to < 120 °C, particularly preferably > 55 to < 90 °C. If HDI is used as component A', the trimerization in step IT is very particularly preferably carried out at > 57 to < 65 °C.

[0057] In step IIT, a second portion of the catalyst component B' (B' T 2) and a second portion of the solvent component C' (C'T2).

[0058] With regard to the manner in which the components B' and C' are supplied, the statements made for step IT (sections 2 to 4 under "Embodiment 2") apply analogously here.

[0059] B'T2 is used in amounts of > 0 to < 0.5 wt.%, preferably > 0 to < 0.1 wt.%, based on the total second subset of component C' used in step IIT (ie based on the total amount of C'T2).

[0060] The total amount of catalyst component B' added corresponds to the sum of the two partial amounts from steps IT and IIT (B'TI + B' T 2). The total amount of catalyst component B' added is generally > 0.001 to < 2 wt.%, preferably > 0.001 to < 1 wt.% and particularly preferably > 0.001 to < 0.2 wt.%, in each case based on the amount of isocyanate component A' used.

[0061] The total amount of solvent component C' added corresponds to the sum of the two partial amounts from steps IIT and IIT (C'TI + C'T2). The total amount of solvent component C' added is preferably > 0.3 to < 5 wt. %, particularly preferably > 1 to < 2 wt. %, based in each case on the amount of isocyanate component A' used.

[0062] The trimerization in step IIT is carried out at reaction temperatures of preferably > 50 to < 120 °C, particularly preferably > 55 to < 90 °C. If HDI is used as component A', the trimerization in step IIT is very particularly preferably carried out at > 57 to < 65 °C. The reaction temperatures in step IP and step IIP can be the same or different.

[0063] In step IIP, the trimerization of component A' is continued until the desired degree of trimerization is reached.

[0064] As soon as the desired degree of trimerization is reached in embodiment 1 or 2, the reaction can be stopped, which can be done chemically or thermally. Thermal stopping is preferred. In the case of chemical stopping, the reaction solution is stopped by adding an acidic compound, an acid and / or an alkylating agent. The preferred thermal stopping takes place either at the selected reaction temperature by simply stirring after the reaction has subsided or by increasing the temperature by up to 50°C and stirring at this temperature. The stopping temperature is preferably slightly increased by up to 20°C compared to the reaction temperature. Thermal stopping is particularly preferably carried out at reaction temperature.

[0065] The processes according to the invention can be carried out as batch processes, semi-batch processes or continuously, in one or more stirred tanks.

[0066] After completion of the trimerization reaction, optionally by terminating, the reaction product is a solution of the isocyanurate group-containing polyisocyanate P in excess monomeric di- and / or polyisocyanate of component A (reaction mixture R), or a solution of the isocyanurate group-containing polyisocyanate P' in excess monomeric di- and / or polyisocyanate of component A' (reaction mixture R').

[0067] In a preferred embodiment of the invention, any monomeric di- and / or polyisocyanate of component A or A' still present in reaction mixture R or R' is separated off by distillation in a downstream step. This is preferably carried out by thin-film distillation in a vacuum, for example at a pressure of less than 1.0 mbar, preferably less than 0.5 mbar, particularly preferably less than 0.2 mbar, under the mildest possible conditions, for example at a temperature of 100 to 200 °C, preferably 120 to 180 °C. The monomeric di- and / or polyisocyanate can be separated off in one stage, but is preferably carried out in several stages. For example, a falling-film evaporator is used as a pre-evaporator, in which the majority of the monomeric di- and / or polyisocyanate is separated off, and further starting isocyanate is separated off in the downstream thin-film evaporator.In this way, high-quality polyisocyanates containing isocyanurate groups are obtained, which have a free monomeric di- and / or polyisocyanate content of a maximum of 0.5 wt.%, preferably a maximum of 0.1 wt.%. The resulting distillates are reused for trimerization.

[0068] In a further embodiment, the monomeric di- and / or polyisocyanates are separated from the reaction product by extraction with suitable solvents that are inert toward isocyanate groups, for example, aliphatic or cycloaliphatic hydrocarbons such as pentane, hexane, heptane, cyclopentane, or cyclohexane. This process is less preferred.

[0069] The resulting low-monomer polyisocyanates containing isocyanurate groups are used as such or dissolved in suitable NCO-inert solvents to form polyisocyanate solutions. The polyisocyanates produced by the processes according to the invention are used in known applications, such as two-component polyurethane coatings or adhesive applications. Furthermore, the polyisocyanates obtained in this way serve, as is known, as starting materials for further derivatives produced therefrom, such as blocked polyisocyanates or hydrophilized polyisocyanates.

[0070] Experimental part:

[0071] Unless otherwise stated, the reactants were used without further purification. Hexamethylene diisocyanate and Desmodur LD were purchased from Covestro Deutschland AG. All other reactants were ordered from Sigma Aldrich (Merck AG): Triton B 40% in methanol, 2-ethylhexanol, n-butanol, 2-ethylhexane-1,3-diol, 4-heptanol, and choline acetate.

[0072] The following standard methods were used:

[0073] NCO values ​​were determined by NCO titration according to M105-ISO 11909.

[0074] Viscosities were determined according to M014-ISO 3219 / A.3.

[0075] The free monomer content was determined using M106-ISO 10283.

[0076] Online reaction monitoring was performed using Raman spectroscopy. A Kaiser Optics RAMAN RXN2 instrument was used, along with the associated sensor, which was inserted into the reaction vessel and a spectrum was recorded every 2 minutes. The band at wavenumber 1760 cm' 1 The C=O band of the isocyanurate can be clearly assigned. In combination with the NCO determination by titration and with the assumption that all reacted NCO groups flow into the isocyanurate, a calibration of the signals was performed.

[0077] Structure of the system

[0078] The system consists of a 0.5-liter jacketed glass reactor (Büchi, Type 2), which can be operated at up to an operating pressure of 6 bar and an operating temperature of 200 °C. The reactor interior is heated by a thermostat connected to the jacket (Huber, Type Ministat 240). The temperature in the thermostat is controlled based on the temperature measured inside the reactor using a thermocouple. A stirrer installed above the reactor lid ensures the most homogeneous mixing possible within the reactor. A Raman probe can be inserted into the reactor via the reactor lid and used for online reaction monitoring. It is also possible to take samples from the reactor using a syringe for offline analysis.

[0079] Batch reaction

[0080] Example 1: Reference test with conventional dosage (not according to the invention)

[0081] 350 g of hexamethylene diisocyanate (HDI) were placed in a 0.5 L stirred reactor and heated to 70 °C to degas the diisocyanate for 60 min at 20 mbar. After venting the reaction vessel and cooling the diisocyanate to 60 °C, 4.6 g of a 0.5 wt. % Triton B solution in 2-ethylhexene were metered into the vessel as quickly as possible while stirring (1000 rpm). After a short waiting period, the reaction began, leading to a decrease in the free NCO content. A degree of trimerization of 10% was quickly reached. Over the course of a further 3 hours, the NCO content continued to decrease, albeit at a slower rate than before.

[0082] Example 2: Application of the described method (according to the invention)

[0083] The experiment described in Example 1 was repeated identically until a degree of trimerization of 20% was reached. Then, 1.16 g of 2-ethylhexanol was added as a single portion. After a short waiting time, the NCO value decreased more sharply than in the reference experiment (Example 1). The decrease in the NCO value was excessive, which can be explained by the reaction of free NCO groups with the added alcohol to form urethanes and allophanates. The increased number of isocyanurate units compared to Example 1 was confirmed by Raman spectroscopy.

[0084] Similar experiments were also conducted with n-butanol, 2-ethylhexane-1,3-diol, and 4-heptanol. The combination of choline acetate and 2-ethylhexanol was also confirmed in the experiment.

[0085] Example 3: The special role of alcohol in the comparison experiment (not according to the invention)

[0086] The experiment described in Example 1 was repeated identically until a degree of trimerization of 20% was reached. Then, 5 g of Desmodur LD (Covestro's sales name for 2-ethylhexyl (6-isocyanatohexyl) carbamate) was added as one portion. Compared to Reference Example 1, the NCO value increased minimally because the added component, Desmodur LD, contains free isocyanate groups. Apart from that, the reaction course was unchanged, and no increased number of isocyanurate units was formed.

[0087] Figure 1 shows a comparison of the reaction processes of examples 1-3.

[0088] Description of Figure 1 :

[0089] Example 1 = solid line; Example 2 = dotted line; Example 3 = dashed line. Comparison of three trimerization reactions at 60 °C using Triton B as catalyst and 2-ethylhexanol as alcohol. The arrows indicate the timing of additional additions for Examples 2 and 3. Semi-batch experiments (reduction of reaction time)

[0090] Example 4: Semi-batch test with conventional dosing (not according to the invention)

[0091] A 0.5 L stirred reactor was charged with 350 g of hexamethylene diisocyanate (HDI) and heated to 70 °C to degas the diisocyanate for 60 min at 1 mbar. After venting the reaction vessel and cooling the diisocyanate to 65 °C, a 1.5 wt.% Triton B solution in 2-ethylhexene was added to the vessel at a rate of 0.18 ml / min while stirring (500 rpm). After 10 min, the addition of the catalyst solution was stopped. After a further 30 min, the addition of catalyst solution was resumed at 0.017 ml / min until a total of 1.85 g of catalyst solution had been added to the vessel. The reaction was continued until a degree of trimerization of 11.2% was reached. The reaction was then stopped by adding DBP (dibutyl phosphate; 120 wt.% based on the amount of Triton B used).

[0092] Example 5: Semi-batch experiment using the described method (according to the invention)

[0093] In a 0.5 L stirred reactor, 350 g of hexamethylene diisocyanate (HDI) were placed and heated to 70 °C to degas the diisocyanate for 60 min at 1 mbar. After venting the reaction vessel and cooling the diisocyanate to 65 °C, a 1.9 wt. % Triton B solution in 2-ethylhexene was added to the vessel at a rate of 0.18 ml / min while stirring (500 rpm). After 10 min, the addition of the catalyst solution was stopped. After a further 30 min, at T g = 7.6%, the addition of pure alcohol was resumed at 0.017 ml / min until a total of 1.85 g of catalyst solution and added alcohol were metered into the vessel. The reaction continued until a degree of trimerization reached 11.2%. The reaction was then stopped by adding DBP (dibutyl phosphate; 120 wt.% based on the amount of Triton B used).

[0094] Table 1: Comparison of examples 4 and 5 in terms of response times:

[0095] Table 1

[0096] As can be seen from Table 1, the reaction starts faster and the reaction time is shortened in the case of the invention. The raw materials produced in Examples 4 and 5 were distilled in the same way to remove the excess free HDI monomer. As Table 2 shows, the resulting product quality is identical (as expected when using the same amounts of catalyst and alcohol).

[0097] Table 2: Comparison of Examples 4 and 5 with regard to the specifications of the resins obtained after distillation:

[0098] Table 2

Claims

Claims:

1. Process for the preparation of isocyanurate group-containing polyisocyanates P by trimerization A) at least one organic di- or polyisocyanate having independently aliphatically, cycloaliphatically and / or araliphatically bound isocyanate groups, in the presence B) at least one trimerization catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted quaternary ammonium hydroxides of the choline type and C) at least one alcohol as solvent, comprising or consisting of the following steps I) Placing component A in a reactor, II) Adding the total amount of catalyst component B, as well as a first portion of component C (CTI), and trimerizing component A until a degree of trimerization T is obtained gin the range of > 0.5 to < 25%, preferably from > 0.5 to < 20%, where T g = (NCOo - NCOt) / NCOo, where NCOo corresponds to the amount of free NCO groups originally present in the submitted component A and NCOt corresponds to the amount of free NCO groups in the reaction solution at time t, determined by NCO titration according to M105-ISO 11909, III) Adding a second portion of component C (CT2) while continuing the trimerization of component A.

2. Process for the preparation of isocyanurate group-containing polyisocyanates P' by trimerization A') at least one organic di- or polyisocyanate having independently aliphatically, cycloaliphatically and / or araliphatically bound isocyanate groups, in the presence B') at least one trimerization catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted quaternary ammonium hydroxides of the choline type and C') at least one alcohol as solvent, comprising or consisting of the following steps T) placing component A' in a reactor, IT) Feeding a first portion of catalyst component B' (B'TI), and a first portion of component C' (C'TI), wherein catalyst component B'TI is used in amounts of > 0.6 to < 8 wt.%, preferably > 0.8 to < 5 wt.%, particularly preferably > 0.8 to < 2 wt.%, based on the first portion of component C' (C'TI) used in step IT, and trimerizing component A' until a degree of trimerization T is obtained g ' in the range of > 0.5 to < 25%, preferably from > 0.5 to < 20%, where Tg ' = (NCOo - NCOt) / NCOo, where NCOo corresponds to the amount of free NCO groups originally present in the submitted component A' and NCOt corresponds to the amount of free NCO groups in the reaction solution at time t, determined by NCO titration according to M105-ISO 11909, IIT) Adding a second portion of the catalyst component B' (B' T 2), and a second subset of component C' (C'T2), wherein catalyst component B' T 2 in amounts of > 0 to < 0.5 wt.%, preferably > 0 to < 0.1 wt.% based on the second partial amount of component C' (C' TO) used in step IIT, with continuation of the trimerization of component A'.

3. The process according to claim 1, wherein the at least one organic di- or polyisocyanate (A) is selected from the group consisting of PDI, HDI, MPDI, 1,3- and 1,4-HeXDI, 1,3- and 1,4-XDI and NBDI, or the process according to claim 2, wherein the at least one organic di- or polyisocyanate (A') is selected from the group consisting of PDI, HDI, MPDI, 1,3- and 1,4-H6XDI, 1,3- and 1,4-XDI and NBDI.

4. Process according to claim 1 or 3, wherein at least one benzyltrialkylammonium hydroxide and / or at least one hydroxyalkyl-substituted quaternary ammonium hydroxide of the choline type is used as component B, or process according to claim 2 or 3, wherein at least one benzyltrialkylammonium hydroxide and / or at least one hydroxyalkyl-substituted quaternary ammonium hydroxide of the choline type is used as component B'.

5. The process according to claim 4, wherein benzyltrimethylammonium hydroxide (Triton-B) and / or 2-hydroxyethyltrimethylammonium acetate (choline acetate) is used.

6. Process according to one of claims 1 or 3 to 5, wherein aliphatic and / or cycloaliphatic mono- or diols are used as component C, preferably those having at least one primary alcohol group, or process according to one of claims 2 to 5, wherein aliphatic and / or cycloaliphatic mono- or diols are used as component C', preferably those having at least one primary alcohol group.

7. Process according to one of claims 1 or 3 to 6, wherein catalyst component B is used in amounts of > 0.001 to < 2 wt.%, preferably from > 0.001 to < 1 wt.% and particularly preferably from > 0.001 to < 0.2 wt.%, in each case based on the amount of isocyanate component A used, or process according to one of claims 2 to 6, wherein catalyst component B' is used in amounts of > 0.001 to < 2 wt.%, preferably from > 0.001 to < 1 wt.% and particularly preferably from > 0.001 to < 0.2 wt.%, in each case based on the amount of isocyanate component A' used.

8. The process according to any one of claims 1 or 3 to 7, wherein the catalyst component B is used in amounts of > 0.3 to < 8 wt.%, preferably > 0.5 to < 5 wt.%, particularly preferably > 0.8 to < 2 wt.%, based on the first portion of component C (CTI) used in step II.

9. Process according to one of claims 1 or 3 to 8, wherein the trimerization in step II is carried out at reaction temperatures of > 50 to < 120 °C, preferably > 55 to < 90 °C, or process according to one of claims 2 to 7, wherein the trimerization in step IT is carried out at reaction temperatures of > 50 to < 120 °C, preferably > 55 to < 90 °C.

10. The process according to any one of claims 1 or 3 to 9, wherein the total amount of solvent component C (CTI + C 2) fed in steps II and III is > 0.3 to < 5 wt.%, preferably > 1 to < 2 wt.%, in each case based on the amount of isocyanate component A used, or the process according to any one of claims 2 to 7 or 9, wherein the total amount of solvent component C' (C'TI + C 2) fed in steps II' and III is > 0.3 to < 5 wt.%, preferably > 1 to < 2 wt.%, in each case based on the amount of isocyanate component A' used.

11. Process according to one of claims 1 or 3 to 10, wherein the trimerization in step III is carried out at reaction temperatures of > 50 to < 120 °C, preferably > 55 to < 90 °C, or process according to one of claims 2 to 7 or 9 or 10, wherein the trimerization in step IIT is carried out at reaction temperatures of > 50 to < 120 °C, preferably > 55 to < 90 °C.

12. The process according to any one of claims 1 to 11, wherein the process is carried out as a batch process, semi-batch process or continuously, in one or more stirred tanks.

13. Process according to one of claims 1 or 3 to 12, wherein the trimerization of component A is stopped chemically or thermally, preferably thermally, when a desired degree of trimerization is reached, or process according to one of claims 2 to 7 or 9 to 12, wherein the trimerization of component A' is stopped chemically or thermally, preferably thermally, when a desired degree of trimerization is reached.

14. Process according to one of claims 1 or 3 to 13, characterized in that in a subsequent step, any monomeric di- and / or polyisocyanate of component A still present is separated from the reaction product by distillation, or process according to one of claims 2 to 7 or 9 to 13, characterized in that in a subsequent step, any monomeric di- and / or polyisocyanate of component A' still present is separated from the reaction product by distillation.

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