Method for producing polyisocyanates containing isocyanurate groups

Abstract

The invention relates to a method for producing polyisocyanates P containing isocyanurate groups by trimerizing A) in the presence of B) and C): A) at least one organic diisocyanate or polyisocyanate having isocyanate groups which are aliphatic, cycloaliphatic and / or araliphatic bonded independently of one another, b) at least one trimerisation catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxide, quaternary trialkylammonium hydroxide and hydroxyalkyl-substituted choline-type quaternary ammonium hydroxide, C) at least one alcohol as solvent.

Description

[0001] The method of preparing polyisocyanates containing isocyanurate groups by trimerizing monomeric diisocyanates and / or polyisocyanates is well known.

[0002] Trimeric catalysts are typically used, such as quaternary tetraalkyl or trialkylaryl ammonium hydroxides, like Triton-B, and hydroxyalkyl-substituted choline-type quaternary ammonium hydroxides, such as acetylcholine.

[0003] The known method in the prior art (e.g., EP 2 700 665 A1) proceeds as follows: First, an alcoholic solution of catalyst is added to the isocyanate component to be trimerized. This initiates an exothermic reaction, raising the temperature of the reaction mixture. In subsequent processes, the exothermic reaction is controlled by adding a matching amount of catalyst solution.

[0004] Surprisingly, it has now been found that reaction behavior can be improved by only metering the alcohol after the initial addition of the catalyst solution to initiate the reaction, without metering any further catalyst. This metering behavior results in less catalyst consumption while keeping the reaction time constant; or, for semi-batch methods, shorter reaction times due to faster reaction initiation, and for cascade methods, increased throughput while keeping the catalyst amount constant. In the first case, less terminating agent is required to terminate the reaction due to less catalyst consumption, and less catalyst residue in the product, thus improving product quality (less tendency for discoloration). The shorter reaction time means the method is more economical. Furthermore, since the amounts of catalyst and alcohol can be controlled independently, reaction conditions can be better tuned according to the quality of the diisocyanate used (relative to the acidic component).

[0005] The subject of this invention is a method for preparing polyisocyanate P containing isocyanurate groups by trimerizing A) in the presence of B) and C). A) At least one organic diisocyanate or polyisocyanate having isocyanate groups that are independently bonded to each other by aliphatic, alicyclic, and / or aryliphatic bonds. B) At least one trimerizing catalyst selected from quaternary tetraalkylammonium hydroxide, quaternary trialkylarylammonium hydroxide, and hydroxyalkyl-substituted choline-type quaternary ammonium hydroxide. C) At least one alcohol as a solvent. The method includes or is composed of the following steps. I) Component A is pre-loaded into the reactor. II) Add the full amount of catalyst component B and the first portion of component C (C T1 ), and trimerize component A until a trimerization degree T of ≥0.5% to ≤25%, preferably ≥0.5% to ≤20%, is obtained. g ,in T g = (NCO0– NCO t ) / NCO0, in NCO0 corresponds to the amount of free NCO groups initially present in the pre-loaded component A. NCO t Corresponding to the amount of free NCO groups in the reaction solution at time t, In each case, the determination was performed by NCO titration according to M105-ISO 11909. III) Add the second portion of component C (C T2 ), to continue the trimerization of component A.

[0006] The above method will be referred to as Implementation Scheme 1.

[0007] Alternatively, a high concentration of catalyst alcohol solution can be added first, and then a low concentration of catalyst solution can be added later after the reaction begins.

[0008] Therefore, the subject of this invention is still the method for preparing polyisocyanate P' containing isocyanurate groups by trimerizing A') in the presence of B') and C'). A') At least one organic diisocyanate or polyisocyanate having isocyanate groups independently bonded to each other by aliphatic, alicyclic, and / or aryliphatic bonds. B') At least one trimerizing catalyst selected from quaternary tetraalkylammonium hydroxide, quaternary trialkylarylammonium hydroxide, and hydroxyalkyl-substituted choline-type quaternary ammonium hydroxide. C') At least one alcohol as a solvent The method includes or is composed of the following steps. I') Component A' is preloaded into the reactor. II') Add the first portion of catalyst component B'(B') T1 ) and the first part of the component C' (C' T1 ), Catalyst component B' T1 The amount used is ≥0.6 wt% to ≤8 wt%, preferably ≥0.8 wt% to ≤5 wt%, particularly preferably ≥0.8 wt% to ≤2 wt%, based on the amount of component C'(C') used in step II'. T1 )count, And make component A' trimerize until a trimerization degree T of ≥0.5% to ≤25%, preferably ≥0.5% to ≤20%, is obtained. g ',in T g ' = (NCO0– NCOt ) / NCO0, in NCO0 corresponds to the amount of free NCO groups initially present in the pre-loaded component A'. NCO t Corresponding to the amount of free NCO groups in the reaction solution at time t, In each case, the determination was performed by NCO titration according to M105-ISO 11909. III') Add the second portion of catalyst component B'(B') T2 ) and the second part of the component C' (C' T2 To continue the trimerization of component A', Catalyst component B' T2 The amount used is >0% by weight to ≤0.5% by weight, preferably >0% by weight to ≤0.1% by weight, based on the amount of component C' (C') used in the second part of step III'. T2 )count.

[0009] This method will be referred to as Implementation Scheme 2.

[0010] In this invention, an aliphatic compound refers to a compound containing only open-chain aliphatic groups, wherein these groups may be branched or unbranched. An alicyclic compound refers to a compound containing at least one alicyclic ring system. An aryliphatic compound refers to a compound containing at least one aryliphatic group.

[0011] To implement the method of the present invention, all organic diisocyanates or polyisocyanates with an average molecular weight of 154-600 g / mol, in pure form or in any mixture thereof, may be used, having an isocyanate group independently bonded to each other aliphatic, alicyclic, and / or aryliphatic. Examples include: pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), 2-methylpentane-1,5-diisocyanate (MPDI), 1,3- and 1,4-bis(isocyanate methyl)cyclohexane (1,3- and 1,4-H6-XDI), 1,3- and 1,4-bis(isocyanate methyl)benzene (1,3- and 1,4-XDI), 3(4)-isocyanate methyl- 1-Methylcyclohexyl isocyanate (IMCI); isophorone diisocyanate (IPDI), bis(isocyanate methyl)norbornene (NBDI), 4-isocyanate methyl octane-1,8-diisocyanate (triisocyanate nonane, TIN), 1,3-bis(isocyanate methyl)benzene, 1,3-bis(2-isocyanate propyl-2)benzene and bis(4(2)-isocyanate cyclohexyl)methane (H 12 MDI, Desmodur W, Covestro AG products). Here, the method by which the above (poly)isocyanates are prepared, i.e., whether or not phosgene is used, is irrelevant.

[0012] Preferably, the at least one organic diisocyanate or polyisocyanate is selected from PDI, HDI, MPDI, 1,3- and 1,4-H6XDI, 1,3- and 1,4-XDI, and NBDI. Particularly preferred are HDI or mixtures of HDI with PDI, MPDI, 1,3- and 1,4-H6XDI, 1,3- and 1,4-XDI, and / or NBDI.

[0013] In step I of embodiment 1, component A can be degassed under reduced pressure and optionally with a heat input. Preferably, component A is degassed in step I. This also applies to component A' in step I' of embodiment 2.

[0014] In the method of the present invention, at least one quaternary trialkylarylammonium hydroxide and / or at least one hydroxyalkyl-substituted choline-type quaternary ammonium hydroxide is preferably used as catalyst component B or B'. More preferably, at least one benzyltrialkylammonium hydroxide and / or at least one hydroxyalkyl-substituted choline-type quaternary ammonium hydroxide is used. Particularly preferred are benzyltrimethylammonium hydroxide (Triton-B) and / or 2-hydroxyethyltrimethylammonium acetate (acetic acid choline).

[0015] As solvent component C or C', any aliphatic and / or alicyclic alcohol is preferred, with aliphatic alcohols being more preferred, particularly low molecular weight mono- or diols. 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 mixture of these alcohols. Alcohols containing at least one primary alcohol group are particularly preferred. Very particularly preferred are 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 mixture of these alcohols.

[0016] In embodiment 1, the at least one alcohol C used in step II may be the same as or different from the at least one alcohol used in step III. Similarly, in embodiment 2, the at least one alcohol C' used in step II' may be the same as or different from the at least one alcohol used in step III'.

[0017] Implementation Plan 1: In step II, the entire amount of catalyst component B and the first portion of solvent component C (C T1 ) is added to the reactor and component A is trimerized until a trimerization degree T of ≥0.5% to ≤25%, preferably ≥0.5% to ≤20%, is obtained. g .

[0018] Components B and C are preferably added in such a manner that at least a portion of the total amount of catalyst component B is present in a form dissolved in at least a portion of the first portion of solvent component C. In this case, the following embodiment is preferred: The entire amount of component B is added to the reactor in the form of a solution dissolved in the entire first portion of component C (implementation a), wherein the addition may be continuous or discontinuous.

[0019] All of component B is added to the reactor in the form of a first portion dissolved in a first portion of component C, and the remaining portion of the first portion of component C is added to the reactor as pure component C (Scheme b), wherein these two processes can be carried out independently and continuously or discontinuously. Here, "pure component C" refers to a catalyst in which component C does not contain component B.

[0020] The amount of catalyst component B is preferably ≥0.3 wt% to ≤8 wt%, particularly preferably ≥0.5 wt% to ≤5 wt%, and very particularly preferably ≥0.8 wt% to ≤2 wt%, based on the total amount of component C used in step II, i.e., based on C. T1 count.

[0021] The amount of catalyst component B is typically ≥0.001 wt% to ≤2 wt%, preferably ≥0.001 wt% to ≤1 wt%, more preferably ≥0.001 wt% to ≤0.2 wt%, based on the amount of isocyanate component A used in each case.

[0022] Step II can be performed such that trimerization begins either during the addition of component B or after its addition. This may be affected by heat. The former possibility is preferred.

[0023] The trimerization in step II is carried out at a reaction temperature preferably ≥50°C to ≤120°C, more preferably ≥55°C to ≤90°C. If HDI is used as component A, the trimerization in step II is particularly preferably carried out at a temperature ≥57°C to ≤65°C.

[0024] In step III, the second portion of solvent component C (C T2 It is added to the reactor. This can be done continuously or discontinuously.

[0025] The total amount of solvent component C added corresponds to the sum of the two portions in steps II and III (C T1 +C T2 The total amount of solvent component C added is preferably ≥0.3% by weight to ≤5% by weight, more preferably ≥1% by weight to ≤2% by weight, based on the amount of isocyanate component A used in each case.

[0026] The trimerization in step III is preferably carried out at a reaction temperature of ≥50°C to ≤120°C, more preferably ≥55°C to ≤90°C. If HDI is used as component A, the trimerization in step II is particularly preferably carried out at a reaction temperature of ≥60°C to ≤65°C.

[0027] The reaction temperatures in steps II and III can be the same or different.

[0028] In step III, the trimerization of component A continues until the desired degree of trimerization is achieved.

[0029] Implementation Plan 2: In step II', the first portion of catalyst component B' (B' T1 ) and the first portion of solvent component C'(C' T1 The component A' is added to the reactor and allowed to trimerize until a trimerization degree T of ≥0.5% to ≤25%, preferably ≥0.5% to ≤20%, is obtained. g '.

[0030] In this case, components B' and C' are preferably added in such a manner that at least a portion of the first portion of catalyst component B' is present in a form dissolved in at least a portion of the first portion of solvent component C'. Here, the following embodiments are preferred: The entire first portion of component B' is added to the reactor in the form of component C' dissolved in the entire first portion (implementation a'), wherein the addition may be continuous or discontinuous.

[0031] The entire first portion of component B' is added to the reactor as a first portion dissolved in the first portion of component C', and the remaining portion of the first portion of component C' is added to the reactor as pure component C' (implementation b'), wherein these two processes can be carried out independently and continuously or discontinuously. Here, "pure component C'" means that C' does not contain component B' of the catalyst.

[0032] B' T1The amount used is ≥0.6 wt% to ≤8 wt%, preferably ≥0.8 wt% to ≤5 wt%, particularly preferably ≥0.8 wt% to ≤2 wt%, based on the total amount of component C' used in step II' (i.e., based on the total amount of C'). T1 )count.

[0033] Step II' can be performed such that trimerization begins either during the addition of component B' or after the addition of component B'. This may be affected by heat. The former possibility is preferred.

[0034] The trimerization in step II' is carried out at a reaction temperature preferably ≥50°C to ≤120°C, more preferably ≥55°C to ≤90°C. If HDI is used as component A', the trimerization in step II' is particularly preferably carried out at a temperature ≥57°C to ≤65°C.

[0035] In step III', the second portion of catalyst component B' (B' T2 ) and the second portion of solvent component C'(C' T2 Add it to the reactor.

[0036] The statements made regarding the manner and type of addition of components B' and C' also apply to step II' (paragraphs 2 to 4 under "Implementation Scheme 2").

[0037] B' T2 The amount used is >0% by weight to ≤0.5% by weight, preferably >0% by weight to ≤0.1% by weight, based on the total amount of component C' used in step III' (i.e., based on the total amount of C'). T2 )count.

[0038] The total amount of catalyst component B' added corresponds to the sum of the two portions in steps II' and III' (B' T1 +B' T2 The total amount of catalyst component B' added is typically ≥0.001 wt% to ≤2 wt%, preferably ≥0.001 wt% to ≤1 wt%, more preferably ≥0.001 wt% to ≤0.2 wt%, based on the amount of isocyanate component A' used in each case.

[0039] The total amount of solvent component C' added corresponds to the sum of the two portions in steps II' and III' (C' T1 + C' T2 The total amount of solvent component C' added is preferably ≥0.3% by weight to ≤5% by weight, more preferably ≥1% by weight to ≤2% by weight, based on the amount of isocyanate component A' used in each case.

[0040] The trimerization in step III' is carried out at a reaction temperature preferably ≥50°C to ≤120°C, more preferably ≥55°C to ≤90°C. If HDI is used as component A', the trimerization in step II' is particularly preferably carried out at ≥57°C to ≤65°C.

[0041] The reaction temperatures in steps II' and III' can be the same or different.

[0042] In step III', the trimerization of component A' continues until the desired degree of trimerization is achieved.

[0043] Once the desired degree of trimerization is reached in embodiment 1 or 2, the reaction can be terminated, which can be done chemically or thermally. Thermal termination is preferred. In the case of chemical termination, the reaction is terminated by adding an acidic compound, an acid, and / or an alkylating agent. Preferred thermal termination is either carried out at the selected reaction temperature by simply continuing stirring after reaction termination, or by raising the temperature by up to 50°C and continuing stirring at that temperature. Preferably, the termination temperature is slightly higher than the reaction temperature by up to 20°C. Particularly preferred is thermal termination at the reaction temperature.

[0044] The method of the present invention can be carried out in one or more mixing tanks in a batch, semi-batch or continuous manner.

[0045] Optionally, after the trimerization reaction is terminated, the remaining reaction products are either a solution of polyisocyanate P containing isocyanurate groups in excess monomeric diisocyanate and / or polyisocyanate of component A (reaction mixture R), or a solution of polyisocyanate P' containing isocyanurate groups in excess monomeric diisocyanate of component A' (reaction mixture R').

[0046] In a preferred embodiment of the invention, in a downstream step, the monomeric diisocyanate and / or polyisocyanate of the remaining component A or A' is separated from the reaction mixture R or R' by distillation. This is preferably carried out under vacuum (e.g., pressure below 1.0 mbar, preferably below 0.5 mbar, more preferably below 0.2 mbar) using thin-film distillation under the mildest possible conditions (e.g., temperature from 100°C to 200°C, preferably from 120°C to 180°C). The monomeric diisocyanate and / or polyisocyanate can be separated in a single stage, but multi-stage separation is preferred. For example, a falling film evaporator is used as a pre-evaporator, in which most of the monomeric diisocyanate and / or polyisocyanate is separated; the remaining starting isocyanate is separated in a downstream thin-film evaporator. This yields a high-quality polyisocyanate containing isocyanurate groups, with a free monomeric diisocyanate and / or polyisocyanate content of up to 0.5% by weight, preferably up to 0.1% by weight. The resulting distillate is then used for trimerization.

[0047] In another embodiment, the monomeric diisocyanate and / or polyisocyanate are separated from the reaction product by extraction with a suitable solvent inert to the isocyanate group (e.g., aliphatic or alicyclic hydrocarbons such as pentane, hexane, heptane, cyclopentane, or cyclohexane). This method is less preferred.

[0048] The resulting monomer-poor polyisocyanates containing isocyanurate groups can be used as is, or dissolved in a suitable solvent inert to NCO groups, to form polyisocyanate solutions. The polyisocyanates prepared according to the method of the invention are used in known applications, such as two-component polyurethane paints or adhesives. The resulting polyisocyanates are also, as known, used as starting materials for other derivatives made therefrom, such as blocked polyisocyanates or hydrophilic polyisocyanates.

[0049] Experimental section: Unless otherwise stated, all reactants were used directly without further purification. Hexamethylene diisocyanate and Desmodur LD were purchased from Covestro Deutschland AG. All other reactants were purchased from Sigma Aldrich (Merck AG): 40% Triton B methanol solution, 2-ethylhexanol, n-butanol, 2-ethylhexane-1,3-diol, 4-heptanol, and acetylcholine.

[0050] The following standard methods shall be adopted: The NCO value was determined by NCO titration according to M105-ISO 11909.

[0051] Viscosity was determined according to M014-ISO 3219 / A.3.

[0052] The free monomer content was determined using M106-ISO 10283.

[0053] Online reaction monitoring was performed using Raman spectroscopy. A Kaiser Optics RAMAN RXN2 instrument was used, with the relevant measurement sensors placed in the reaction vessel, and spectra were recorded every 2 minutes. The C=O band of isocyanurate was uniquely assigned to a band at a wavenumber of 1760 cm⁻¹. The signal was calibrated by combining the NCO group content layer obtained by titration and assuming that all NCO groups reacted into the isocyanurate.

[0054] Equipment Structure The equipment consists of a 0.5-liter jacketed glass reactor (Büchi, Model 2), which can operate at a maximum working pressure of 6 bar and a working temperature of 200°C. The internal space of the reactor is heated by a thermostat (Huber, Ministat 240) connected to the jacket. The temperature control of the thermostat is based on the temperature measured by thermocouples within the reactor's internal space. A stirrer inserted through the reactor lid ensures thorough and uniform mixing within the reactor. A Raman probe can be inserted through the reactor lid for online reaction monitoring. Furthermore, samples can be taken from the reactor for offline analysis using a syringe.

[0055] Intermittent reaction Example 1: Reference experiment using conventional dosage (not the present invention) 350 g of hexamethylene diisocyanate (HDI) was pre-loaded into a 0.5 L stirred reactor and heated to 70 °C to degas the diisocyanate at 20 mbar for 60 min at this temperature. After venting the reaction vessel and cooling the diisocyanate to 60 °C, 4.6 g of a 0.5 wt% Triton B 2-ethylhexanol solution was metered into the vessel as quickly as possible with stirring (1000 rpm). After a short waiting period, the reaction began, causing a decrease in the free NCO value. Trimerization was rapidly reached at 10%. Over the next 3 hours, the NCO value continued to decrease, but at a slower rate than before.

[0056] Example 2: Application of the method (according to the present invention) The experiment described in Example 1 was repeated until a trimerization degree of 20% was achieved. Then, 1.16 g of 2-ethylhexanol was added at once. After a short waiting period, the NCO value decreased more significantly than in the reference experiment (Example 1). The decrease in NCO value exceeded the range that could be explained by the reaction of free NCO groups with the added alcohol to form urethane and urethane esters. Raman spectroscopy confirmed that the number of isocyanurate units was increased compared to Example 1.

[0057] Similar experiments were also conducted using n-butanol, 2-ethylhexane-1,3-diol, and 4-heptanol. The experiments also confirmed the effectiveness of the acetylcholine / 2-ethylhexanol combination.

[0058] Example 3: The special role of alcohols in comparative experiments (not of this invention) The method described in Example 1 was repeated until a trimerization degree of 20% was achieved. Then, 5 grams of Desmodur LD (Covestro's trade name for (6-isocyanate-hexyl)carbamate 2-ethylhexyl ester) was added at once. Compared to Reference Example 1, the NCO value increased only minimally because the added Desmodur LD component contained free isocyanate groups. Apart from this, no other reaction proceeded, and the number of isocyanurate units did not increase.

[0059] Figure 1 A comparison of the reaction processes in Examples 1-3 is shown.

[0060] Figure 1 Description: Example 1 = solid line; Example 2 = dotted line; Example 3 = dashed line. Three trimerization reactions were compared at 60°C using Triton B as a catalyst and 2-ethylhexanol as the alcohol. Arrows indicate the times when additional metered amounts were added in Examples 2 and 3.

[0061] Semi-batch experiment (shortening the reaction time) Example 4: A semi-intermittent experiment using conventional dosage (not part of this invention) 350 g of hexamethylene diisocyanate (HDI) was pre-loaded into a 0.5 L stirred reactor and heated to 70 °C to degas the diisocyanate at 1 mbar for 60 min at this temperature. After venting the reaction vessel and cooling the diisocyanate to 65 °C, a 1.5 wt% Triton B 2-ethylhexanol solution was metered into the vessel at 0.18 mL / min with stirring (500 rpm). The addition of catalyst solution was stopped after 10 min. After another 30 min, the catalyst solution was continued to be added at 0.017 mL / min until a total of 1.85 g of catalyst solution had been metered into the vessel. The reaction continued until a trimerization degree of 11.2% was reached. The reaction was now terminated by adding DBP (dibutyl phosphate; 120 wt% based on the amount of Triton B used).

[0062] Example 5: A semi-intermittent experiment conducted using the method described above (according to the present invention) 350 g of hexamethylene diisocyanate (HDI) was pre-loaded into a 0.5 L stirred reactor and heated to 70 °C to degas the diisocyanate at 1 mbar for 60 min at this temperature. After venting the reaction vessel and cooling the diisocyanate to 65 °C, a 1.9 wt% Triton B 2-ethylhexanol solution was metered into the vessel at 0.18 mL / min with stirring (500 rpm). The addition of catalyst solution was stopped after 10 min. After another 30 min, when T… g At 7.6%, pure alcohol was added at a rate of 0.017 mL / min until the total amount of catalyst solution and alcohol added to the container was 1.85 g. The reaction continued until a trimerization degree of 11.2% was reached. The reaction was then terminated by adding DBP (dibutyl phosphate; 120 wt% based on the amount of Triton B used).

[0063] Table 1: Comparison of reaction times in Examples 4 and 5: Trimerization 0% (Experiment begins) 11.2% (target value for the experiment) Waiting period (minutes) The target value will be reached after x minutes. Example 4 12 122 Example 5 4 64 Table 1.

[0064] As can be seen from Table 1, the reaction starts faster and the reaction time is shortened in the case of the present invention.

[0065] The crude products generated in Examples 4 and 5 were distilled using the same method to remove excess free HDI monomer. As shown in Table 2, the resulting products were of the same quality (as expected when using the same amounts of catalyst and alcohol).

[0066] Table 2: Comparison of the specifications of the resins obtained after distillation in Examples 4 and 5: Example 4 Example 5 NCO value (%) 22.8 22.7 Viscosity / mPas @ 23℃ 1300 1200 Free monomer content 0.03 0.04 Table 2.

Claims

1. Process for the preparation of isocyanurate group-containing polyisocyanates P by trimerization in the presence of B) and C) A) at least one organic di- or polyisocyanate having aliphatically, cycloaliphatically and / or araliphatically bound isocyanate groups independently of one another, B) at least one trimerization catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted choline-type quaternary ammonium hydroxides, C) at least one alcohol as solvent, which comprises or consists of the following steps I) preloading component A in a reactor, II) adding the entire amount of catalyst component B and the first part of component C (C T1 ) and allowing component A to trimerize until a trimerization degree T of ≥ 0.5 % to ≤ 25 %, preferably ≥ 0.5 % to ≤ 20 % is obtained g wherein T g = (NCO0 – NCO t ) / NCO0, wherein NCO0 corresponds to the amount of free NCO groups initially present in the preloaded component A, NCO t corresponding to the amount of free NCO groups in the reaction solution at the time t, determined in each case by NCO titration according to M105-ISO 11909, III) adding a second portion of component C (C T2 ) to continue the trimerization of component A.

2. Process for the preparation of isocyanurate group-containing polyisocyanates P' by trimerization in the presence of B') and C') A') at least one organic di- or polyisocyanate having aliphatically, cycloaliphatically and / or araliphatically bound isocyanate groups independently of one another, B') at least one trimerization catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted choline-type quaternary ammonium hydroxides C') at least one alcohol as solvent, which comprises or consists of the following steps I') preloading component A' in a reactor, II') adding a first portion of the catalyst component B' (B T1 ) and a first portion of component C' (C T1 ), wherein the catalyst component B' T1 is used in an amount of > 0.6 wt.-% to < 8 wt.-%, preferably > 0.8 wt.-% to < 5 wt.-%, especially preferred > 0.8 wt.-% to < 2 wt.-%, based on the first part amount of component C' (C T1 ) used in step II', and component A' is trimerized until a trimerization degree T of > 0.5 % to < 25 %, preferably > 0.5 % to < 20 % is obtained g wherein T g = (NCO0 – NCO t ) / NCO0, wherein NCO0 corresponds to the amount of free NCO groups initially present in the preloaded component A', NCO t corresponding to the amount of free NCO groups in the reaction solution at the time t, determined in each case by NCO titration according to M105-ISO 11909, III') adding a second portion of the catalyst component B' (B T2 ) and a second portion of component C' (C T2 ) to continue the trimerization of component A'. wherein the catalyst component B' T2 is used in an amount of > 0 to < 0.5 wt.-%, preferably > 0 to < 0.1 wt.-%, based on the second part of the amount of component C' (C T2 ) used in step III'.

3. 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-H6XDI, 1,3- and 1,4-XDI and NBDI, or 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 choline-type quaternary ammonium hydroxide 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 choline-type quaternary ammonium hydroxide is used as component B'.

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

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

7. The process as claimed in any of claims 1 or 3 to 6, wherein the amount of catalyst component B used is > 0.001 to < 2% by weight, preferably > 0.001 to < 1% by weight, more preferably > 0.001 to < 0.2% by weight, in each case based on the amount of isocyanate component A used, or the process as claimed in any of claims 2 to 6, wherein the amount of catalyst component B' used is > 0.001 to < 2% by weight, preferably > 0.001 to < 1% by weight, more preferably > 0.001 to < 0.2% by weight, in each case based on the amount of isocyanate component A' used.

8. The method according to any one of claims 1 or 3 to 7, wherein the amount of catalyst component B is ≥0.3% by weight to ≤8% by weight, preferably ≥0.5% by weight to ≤5% by weight, particularly preferably ≥0.8% by weight to ≤2% by weight, based on the first portion of component C (C) used in step II. T1 )count.

9. The process as claimed in any of claims 1 or 3 to 8, wherein the trimerization in step II is carried out at a reaction temperature of > 50 to < 120°C, preferably > 55 to < 90°C, or the process as claimed in any of claims 2 to 7, wherein the trimerization in step II' is carried out at a reaction temperature of > 50 to < 120°C, preferably > 55 to < 90°C.

10. The method of any one of claims 1 or 3 to 9, wherein the total amount of solvent component C (C) added in steps II and III T1 + C T2 The amount is ≥0.3% by weight to ≤5% by weight, preferably ≥1% by weight to ≤2% by weight, in each case based on the amount of isocyanate component A used, or the method as described in any one of claims 2 to 7 or 9, wherein the total amount of solvent component C' (C') added in steps II' and III' is ≥0.3% by weight to ≤5% by weight, preferably ≥1% by weight to ≤2% by weight, based on the amount of isocyanate component A used, or the method as described in any one of claims 2 to 7 or 9. T1 + C' T2 The amount is ≥0.3% by weight to ≤5% by weight, preferably ≥1% by weight to ≤2% by weight, in each case based on the amount of isocyanate component A' used.

11. The process as claimed in any of claims 1 or 3 to 10, wherein the trimerization in step III is carried out at a reaction temperature of > 50 to < 120°C, preferably > 55 to < 90°C, or the process as claimed in any of claims 2 to 7 or 9 or 10, wherein the trimerization in step III' is carried out at a reaction temperature of > 50 to < 120°C, preferably > 55 to < 90°C.

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

13. The process as claimed in any of claims 1 or 3 to 12, wherein the trimerization of component A is terminated, when the desired degree of trimerization has been reached, by chemical or thermal means, preferably thermal means, or the process as claimed in any of claims 2 to 7 or 9 to 12, wherein the trimerization of component A' is terminated, when the desired degree of trimerization has been reached, by chemical or thermal means, preferably thermal means.

14. The method of any one of claims 1 or 3 to 13, wherein, In a subsequent step, the monomeric diisocyanates and / or polyisocyanates of component A which are still present are separated off from the reaction product by distillation, or the process as claimed in any of claims 2 to 7 or 9 to 13, characterized in that, in a subsequent step, the monomeric diisocyanates and / or polyisocyanates of component A' which are still present are separated off from the reaction product by distillation.

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