Composition containing isocyanate and isocyanurate groups, and rigid pur / pir foams produced therefrom

Abstract

Compositions containing isocyanate and isocyanurate groups by allowing a pMDI to react in the presence of a trimerization catalyst, and the process for producing a rigid PUR / PIR foam from this composition. The invention further relates to the process for producing the compositions containing isocyanate and isocyanurate groups, to the production of rigid PUR / PIR foams from these compositions, to the rigid foams themselves, and to the use of such rigid foams.

Description

Composition containing isocyanate and isocyanurate groups and PUR / PIR rigid foam materials made therefrom The present invention relates to a composition containing isocyanate and isocyanurate groups for the production of PUR / PIR rigid foams, as well as to the production of the compositions containing isocyanate and isocyanurate groups by partial trimerization of polymeric MDI (pMDI). It further relates to the production of PUR / PIR rigid foams from these compositions, the rigid foams themselves, and the use of such rigid foams. To improve fire safety, polyisocyanurate polyurethane foam systems (PUR / PIR foams) are increasingly being used to manufacture thermally insulating foams, such as those used in cladding house facades. These systems are produced by using a significantly higher than stoichiometric amount of the polymeric polyisocyanate typically used in rigid foam production, relative to the polyol component. Therefore, the polymeric polyisocyanate used has a significant influence on the properties of the rigid foam. A key technical property, in addition to the final properties such as insulation and final strength, is the mechanical strength shortly after the rigid foam is produced. This determines the time after which the rigid foam can be mechanically handled and stacked. It is known that the curing time of a PUR / PIR foam can be influenced by various factors, including the use of oligomeric (multi-nuclear) polyisocyanates. The formation of multi-nuclear isocyanurate structures is achieved through trimerization of polyisocyanates. US 4,743,627 describes PUR / PIR foams with particularly low coloration from compositions containing isocyanate and isocyanurate groups. The process described therein comprises the steps of: (a) trimerization of polymeric MDI in the presence of a trimerization catalyst to obtain an isocyanurate-containing polyisocyanate; (b) deactivation of the trimerization catalyst; and (c) mixing the isocyanurate-containing polyisocyanate with monomeric MDI to form a final product with a viscosity comparable to that of a standard pMDI and a dinuclear content of at least 60% by weight. The final product is used in the production of foams that have a lighter color than those based on standard pMDI.The disadvantage of step c), mixing with monomeric MDI, is the reduction of the isocyanate functionality of the mixture, which has a negative effect on the final properties such as strength of the resulting PUR / PIR rigid foam. US 2009 / 105359 A1 relates to a process for producing a liquid, isocyanurate-modified pMDI with a controlled viscosity. The process comprises the following steps: (a) Trimerization of "conventional pMDI," a trimer-free mixture of monomeric and oligomeric MDI with a viscosity between 30 and 300 mPa*s, in the presence of a trimerization catalyst to obtain an isocyanurate-containing pMDI with a viscosity at 25 °C in the range of 2000 mPa*s to 200,000 mPa*s; (b) deactivation of the catalyst with a catalyst deactivator to obtain a mixture containing isocyanurate-modified pMDI and deactivated catalyst; and (c) mixing the mixture from step (b) with an amount of trimer-free pMDI sufficient to obtain a mixture having a viscosity at 25 °C in the range of 400 mPas to 20,000 mPas and a content of free NCO groups comparable to conventional pMDI having a viscosity between 30 and 1000 mPa*s. The disadvantage is that this three-step process for producing isocyanurate-containing pMDI, which runs over a highly viscous pMDI in an intermediate step, leads to defects in the production of insulation panels. WO 2017 / 046274 A1 discloses a process for producing rigid polyurethane-polyisocyanurate foams (PUR / PIR rigid foams) using an isocyanate blend of predominantly monomeric MDI with polymeric MDI, which is subsequently partially trimerized. The isocyanate blends used according to the invention contain 15-25 wt. % isocyanurate groups and have viscosities of > 1000 mPa*s at 25 °C. Blends with lower viscosities and / or higher isocyanurate contents prove to be disadvantageous, e.g., in terms of storage stability. JP H06 256460 A, JP 2008 260843 A, JP H08 73557 A, JP H08 92346 A, and JP H08 120048 A disclose isocyanurate-modified polyisocyanates and foams produced therefrom. Relatively high catalyst concentrations (greater than 0.5 wt.%) are used to produce the modified polyisocyanates, and the results show no linear relationship between NCO content, viscosity, and isocyanurate content. In each case, an MDI with a viscosity of 130 mPa*s (25°C) is used. Catalyst concentrations above 0.5 wt.% lead to reactivity that is difficult to control. JP S59 163357 A also discloses the production of modified polyisocyanates with high catalyst loadings, which are thermally and not chemically deactivated. However, this has the disadvantage that the non-chemically deactivated catalyst residues can negatively influence the subsequent conversion to polyurethane. Furthermore, the trimerization reaction continues for some time during the thermal deactivation, making it almost impossible to control the product viscosity to a specific level. DE 691 16 583 T2 discloses the trimerization of polyisocyanates using the catalyst tetramethylguanidine, an iminourea derivative. This catalyst cannot be stopped with acid chlorides or hydrochloric acid, which is why methylsulfonic acid is used as a stopper. which has a detrimental effect on the corrosiveness of the composition. EP 3 974 460 A1 discloses an isocyanate formulation containing a radical initiator (tert-butyl peroxybenzoate) and an inhibitor (dibutylhydroxytoluene), the inhibitor being added simultaneously with the radical initiator. The radical initiator is intended to decompose into radicals thermally at elevated temperature during the reaction of the isocyanate formulation with a polyol and initiate a radical polymerization of olefins. The inhibitor is added together with the radical initiator so that the isocyanate formulation remains stable and does not increase in viscosity before use, i.e., during storage, and ultimately become solid. Furthermore, the present invention does not describe any radical initiators, in particular no peroxides or azo compounds. WO 2020 / 221662 A1 also discloses the trimerization of isocyanates using a radical initiator. The reaction is not stopped, and no stopper is added. This means that the trimerization reaction can continue indefinitely until gelation, and the resulting isocyanate cannot be used for a foaming reaction. The object of this invention was to provide, based on the above-mentioned prior art, a polyisocyanate component with which PUR / PIR rigid foams with good initial strength can be produced, allowing early handling and stackability of the resulting insulation panels, and exhibiting good flame retardancy. At the same time, the polyisocyanate component should overcome the disadvantages of the processes described in the prior art (lack of storage stability, poor foam properties, defects in produced panels). This object could surprisingly be achieved by an isocyanurate-containing pMDI with a viscosity of < 2000 mPa*s at 25 °C, in particular < 1000 mPa*s at 25 °C, and a number-average molecular weight Mn of > 350 g / mol, which is obtained directly by trimerization of a conventional polymeric MDI with a monomeric MDI content of < 55 wt.%, in particular < 50 wt.%, and a viscosity of 130 - 400 mPa*s, preferably from 140 to 400 mPa*s at 25 °C, more preferably from 140 - 300 mPa*s at 25 °C, and 5 - < 13 wt.% of isocyanurate groups. The invention therefore relates to a process for producing a composition A2 containing isocyanate and isocyanurate groups, comprising the steps: 1) Allowing a polyisocyanate Al to react in the presence of a trimerization catalyst and 2) stopping the reaction from step 1) using a suitable stopper to obtain composition A2; wherein the trimerization catalyst is not an aminourea, a derivative of an aminourea or a radical initiator, and the concentration of the trimerization catalyst used is < 0.50 wt.% based on Al, in particular < 0.45 wt.%, even more preferably < 0.40 wt.% and very particularly preferably < 0.30 wt.%, and wherein the polyisocyanate Al used in step 1) is polymeric MDI with a content of monomeric diphenylmethane diisocyanate of < 55 wt.%, particularly preferably 30 - 50 wt.% of monomeric diphenylmethane diisocyanate, and a viscosity of 140 - 400 mPa*s (determined according to DIN 53019-1:2008-09, without solvent), and wherein step 2) is carried out when the reaction mixture from step 1) has 5 - <13 wt.% isocyanurate groups and its viscosity < 2000 mPa*s at 25 °C (determined according to DIN 53019-1:2008-09, without solvent). For the purposes of this application, “oligomeric MDI” means a polyisocyanate mixture of higher-nuclear homologues of MDI which have at least 3 aromatic nuclei and an NCO functionality of at least 3. The term "polymeric diphenylmethane diisocyanate," "polymeric MDI," or pMDI is used in the context of the present invention to refer to a mixture of oligomeric MDI and optionally monomeric MDI. Typically, the monomer content of a polymeric MDI is in the range of 30-50 wt.%, based on the total mass of the pMDI. The polyisocyanate Al contains <55 wt.% monomeric MDI, in particular 30 - <50 wt.% monomeric MDI, and has a viscosity of 130 to 400 mPa*s, preferably 140 to 400 mPa*s at 25 °C, and particularly preferably 140 to 300 mPa*s at 25 °C (determined according to DIN 53019-1:2008-09, without solvent). A polymeric MDI with the following composition is particularly preferred: 35-50 wt.% 4,4'-methylidenediphenyl diisocyanate, 1-10 wt.% 2,4'-methylidenediphenyl diisocyanate, >0 to <5 wt.% 2,2'-methylidenediphenyl diisocyanate, and 45 to <64 wt.% higher homologues of methylidenediphenyl diisocyanate (with >3 aromatic nuclei). A composition of 40-50 wt.%, in particular 40-46 wt.%, 4,4'-methylidenediphenyl diisocyanate, 1-5 wt.% 2,4'-methylidenediphenyl diisocyanate, >0 to <5 wt.% 2,2'-methylidenediphenyl diisocyanate, and 45 to <60 wt.% higher homologues of methylidenediphenyl diisocyanate (with >3 aromatic nuclei) is particularly preferred. The polyisocyanate Al is subjected to a trimerization reaction [step (1)]. The trimerization reaction is known per se and described, for example, in WO 2009 / 039332 A,

[0015] -

[0021] , which is referred to here. Suitable trimerization catalysts are, for example, Mannich bases of phenol or phenol derivatives such as 2,4,6-tris(dimethylaminomethyl)phenol and 4,4'-isopropylidenebis[2,6-bis(dimethylaminomethyl)- phenol], potassium acetate, and / or aliphatic quaternary ammonium salts. Methylureas such as 1,1,3,3-tetramethylguanidine are unsuitable as catalysts, as the trimerization reaction is then difficult to stop with acid chlorides. Radical initiators, particularly peroxy and azo compounds, are also unsuitable as catalysts, as the radical-induced trimerization reaction is also difficult to stop. The concentration of the trimerization catalyst used is <0.50 wt.% based on Al, in particular <0.45 wt.%, even more preferably <0.40 wt.%, and most preferably <0.30 wt.%. At higher concentrations, the trimerization reaction proceeds too rapidly, and the correct timing for stopping is difficult to determine. The content of isocyanurate groups (in weight percent) in the isocyanate and isocyanurate group-containing composition A2 obtained after the trimerization reaction is determined as follows: Isocyanurate% (A2) = (NCO% (Al) -NCO% (A2)) / (NCO% (Al) / 2) * 100 The determination of the weight fraction of NCO groups is carried out according to DIN EN 1242:2013. The viscosity data in this application refer to viscosities determined according to DIN 53019-1 (2008-09) (without solvent). The composition of the isocyanate and isocyanurate group-containing compositions A2 or of the isocyanate component A can be determined by gel permeation chromatography (GPC) according to DIN 55672-1:2016-03 at 35 °C in tetrahydrofuran as solvent. The composition A2 or the isocyanate component A exhibits a seventh peak in the GPC (“peak G”, belonging to the fraction with the seventh lowest molecular weight), the peak area of ​​which is preferably > 4.6 area%. The composition A2 or the isocyanate component A preferably has a number-average molecular weight Mn of >350 g / mol. Composition A2 has an isocyanurate group content of 5 - < 13 wt.% isocyanurate groups, a number-average molecular weight Mn of > 350 g / mol, and in GPC a seventh peak belonging to the fraction with the seventh lowest molecular weight, with a peak area of ​​preferably > 4.6 area%, and a viscosity of < 2000 mPa*s at 25 °C, preferably < 1000 mPa*s at 25 °C. The composition A2 produced by the process according to the invention has, in comparison to the compositions from the prior art, a lower content of trimerization catalysts and an advantageous molecular weight distribution, which is noticeable in advantageous properties, e.g. in better surface qualities, during the subsequent processing to PUR / PIR rigid foams. According to the invention, the trimerization reaction is terminated in a controlled manner by adding a deactivator ("stopper"). In principle, any acid chloride or Bronsted acid can be used that is not sulfonic acid, sulfuric acid, or their derivatives (due to the strong corrosiveness of these compounds). Suitable acid chlorides include acetyl chlorides and benzoyl chlorides, and mixtures thereof. A preferred example of acid chlorides is benzoyl chloride; another preferred example is isophthaloyl dichloride. Suitable acids include hydrochloric acid, acetic acid, oxalic acid, and phosphoric acid. Hydrochloric acid, acetic acid, and oxalic acid are preferred. A particularly preferred example of acids is hydrochloric acid. The acid chloride or Bronsted acid can also be used as a solution or dispersion in organic solvents, monomeric MDI, or polymeric MDI. Composition A2, containing isocyanate and isocyanurate groups, obtained after step 2) can be used alone or in a mixture with other isocyanates to produce polymers, particularly PUR and PUR / PIR rigid foams. For example, it is possible to adjust a specific viscosity by blending it with other polyisocyanates. Suitable for this purpose are the aliphatic, cycloaliphatic, and araliphatic di- and / or polyisocyanates known from polyurethane chemistry, and especially aromatic isocyanates. In particular, the isomers and oligomers of MDI and TDI can be used. A further aspect of the present invention is the composition A2 containing isocyanate and isocyanurate groups, which is obtainable by the process according to the invention, and an isocyanate component A comprising the composition A2. The invention also relates to a process for producing a PUR / PIR rigid foam by reacting a PUR / PIR system comprising an isocyanate component A and a polyol formulation B in the presence of blowing agents C and catalysts D, wherein the isocyanate component A comprises a composition A2 according to the invention containing isocyanate and isocyanurate groups. PUR / PIR systems are preferred for the production of composite elements. Foaming typically occurs continuously or discontinuously against at least one facing layer. PUR / PIR rigid foams are obtained by converting the PUR / PIR system. During the conversion, the isocyanate component A and the polyol formulation B are generally reacted in quantities such that the isocyanate index of the foam is > 250 to < 450, preferably > 320 to < 400. The isocyanate index (also called index or isocyanate number) is the quotient of the actual amount of isocyanate groups used [mol] and the stoichiometric amount of isocyanate groups required for complete conversion of all isocyanate-reactive groups [mol], multiplied by 100. Since one mole of an isocyanate group is required for the conversion of one mole of an isocyanate-reactive group, the following applies: Index = (moles of isocyanate groups / moles of isocyanate-reactive groups) • 100 The isocyanate component A has in particular the following properties: <13 wt% isocyanurate groups, 20 - 50 wt.%, preferably 20 - 40 wt.%, monomeric MDI, NCO content of 23 - 30 wt.% (DIN EN 1242:2013), each based on the total weight of the isocyanate component A, and a viscosity of < 2000 mPa*s at 25 °C, preferably < 1000 mPa*s at 25 °C. To prepare the isocyanate component A, the composition A2 according to the invention containing isocyanate and isocyanurate groups can optionally be blended with other isocyanates, e.g., to achieve a lower or higher viscosity. In a preferred embodiment, the composition A2 according to the invention containing isocyanate and isocyanurate groups is used without blending with other isocyanates. Isocyanates used for blending with the composition A2 according to the invention containing isocyanate and isocyanurate groups are the customary aliphatic, cycloaliphatic, araliphatic di- and / or polyisocyanates, and in particular aromatic isocyanates known from polyurethane chemistry. Aromatic isocyanates, in particular the homologues and isomers of the MDI series, are particularly preferred. Furthermore, the isocyanates suitable for blending can be polyurethane prepolymers or modified isocyanates.The term "polyurethane prepolymer" specifically refers to reactive intermediates in the reaction of isocyanates to polyurethane polymers. They are prepared by reacting a polyol component with an excess of an isocyanate component. Preferred modified isocyanates include: urea-modified isocyanates; biuret-modified isocyanates; urethane-modified isocyanates; isocyanurate-modified isocyanates; allophanate-modified isocyanates; carbodiimide-modified isocyanates; uretdione-modified isocyanates, and uretonimine-modified isocyanates. Such modified isocyanates are commercially available and are prepared by reacting an isocyanate with a less than stoichiometric amount of an isocyanate. Isocyanate-reactive compound or with itself. In particular, the isomers and oligomers of MDI and TDI can be used for blending. Compounds based on polyesters or polyethers are preferably used as polyols for polyol formulation B. The functionality of the polyether and / or polyester is generally 1.9 to 8, preferably 1.9 to 7, particularly preferably 1.9 to 6. The polyols in particular have a hydroxyl number greater than 70 mg KOH / g, preferably greater than 100 mg KOH / g, and particularly preferably greater than 120 mg KOH / g. A generally suitable upper limit for the hydroxyl number is 1000 mg KOH / g, preferably 900 mg KOH / g, and especially 800 mg KOH / g. The OH numbers stated above refer to the total polyols in polyol formulation B; this does not exclude the possibility that individual components of the mixture may have higher or lower values. Polyol formulation B preferably contains polyether polyols which are prepared from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical by known processes, for example by anionic polymerization with alkali hydroxides, such as sodium or potassium hydroxide, or alkali alkoxides, such as sodium methylate, sodium or potassium ethylate, or potassium isopropylate, as catalysts and with the addition of at least one starter molecule containing 2 to 8, preferably 2 to 6, reactive hydrogen atoms, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate, etc., or bleaching earth, as catalysts. Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, styrene oxide, and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately one after the other, or as mixtures.Suitable starter molecules are alcohols such as glycerol, trimethylolpropane (TMP), pentaerythritol, sucrose, sorbitol, as well as amines such as methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine, naphthylamine, ethylenediamine, diethylenetriamine, 4,4'-methylenedianiline, 1,3-propanediamine, 1,6-hexanediamine, ethanolamine, diethanolamine, triethanolamine and the like. Furthermore, condensation products of formaldehyde, phenol and diethanolamine or ethanolamine, formaldehyde, alkylphenols and diethanolamine or ethanolamine, formaldehyde, bisphenol A and diethanolamine or ethanolamine, formaldehyde, aniline and diethanolamine or ethanolamine, formaldehyde, cresol and diethanolamine or ethanolamine, formaldehyde, toluidine and diethanolamine or ethanolamine as well as formaldehyde, toluenediamine (TDA) and diethanolamine or ethanolamine and the like can be used as starter molecules.TMP and TDA are preferred as starter molecules. Polyol formulation B may contain crosslinking agents as an additional component. Crosslinking agents are Compounds that have a molecular weight of 60 to less than 400 g / mol and contain at least three isocyanate-reactive hydrogen atoms are understood. An example of this is glycerol. The crosslinkers are generally used in an amount of 1 to 10 wt. %, preferably 2 to 6 wt. %, based on the total weight of polyol formulation B (but excluding physical blowing agents). Polyol formulation B may also contain chain extenders to increase the crosslinking density. Chain extenders are understood to be compounds that have a molecular weight of 60 to less than 400 g / mol and contain two isocyanate-reactive hydrogen atoms. Examples include butanediol, diethylene glycol, dipropylene glycol, and ethylene glycol. The chain extenders are generally used in an amount of 2 to 20 wt. %, preferably 4 to 15 wt. %, based on the total weight of polyol formulation B (but excluding physical blowing agents). Crosslinkers and chain extenders can be used individually or in combination in the polyol mixture. Chemical and / or physical blowing agents (C) are also used to produce PUR / PIR rigid foams. Preferred chemical blowing agents are water or carboxylic acids, especially formic acid. The chemical blowing agent is generally used in an amount of 0.1 to 5 wt.%, especially 1.0 to 3.0 wt.%, based on the weight of component B. Physical blowing agents are compounds that are dissolved or emulsified in the starting materials used in polyurethane production and evaporate under the conditions of polyurethane formation. These include, for example, hydrocarbons, halogenated hydrocarbons, and other compounds such as perfluorinated alkanes, such as perfluorohexane, chlorofluorocarbons, as well as ethers, esters, ketones, and / or acetals. These are typically used in an amount of 1 to 30 wt.%, preferably 2 to 25 wt.%, particularly preferably 3 to 20 wt.%, based on the total weight of component B. Catalysts D are also used to produce the PUR / PIR rigid foams. Catalysts D used to accelerate the reaction of the hydroxyl-containing compounds of component B with the isocyanate groups of component A are usually and preferably organic tin compounds, such as tin(II) salts of organic carboxylic acids, and / or basic amine compounds, preferably tertiary amines, such as triethylamine, and / or 1,4-diazabicyclo-(2,2,2)-octane. Catalysts D used to form isocyanurate groups in the production of the PUR / PIR rigid foams are usually metal carboxylates, preferably Potassium acetate or potassium octoate and their solutions are used. In PUR / PIR rigid foams, a mixture of catalysts is used to accelerate the reaction of the hydroxyl-containing compounds of component B with the isocyanate groups of component A, and of catalysts to form isocyanurate groups. The catalysts are generally used in an amount of 0.001 to 5 wt.% catalyst, based on the weight of component B. If necessary, additional auxiliaries and additives E can also be incorporated into the PUR / PIR system. These are understood to be the auxiliaries and additives known and customary in the art. These can be added to the polyol component B or directly to the reaction mixture. Examples include surfactants, foam stabilizers, cell regulators, fillers, dyes, pigments, flame retardants, antistatic agents, hydrolysis inhibitors, and / or fibrostatic and bacteriostatic substances. The invention is also directed to a PUR / PIR rigid foam obtainable by a process according to the invention. PUR / PIR rigid foams within the meaning of the present invention are, in particular, those PUR / PIR foams whose bulk density according to DIN EN ISO 3386-1-98 in the version of September 2010 is in the range of 15 kg / m 3 up to 300 kg / m 3and whose compressive strength according to DIN EN 826 in the version of May 1996 is in the range of 0.1 MPa to 3 MPa. Surprisingly, it was found that these PUR / PIR rigid foams exhibit improved stackability compared to rigid foams produced with a conventional MDI or a pMDI with higher isocyanurate content. This is measured in the form of the indentation depth with a defined weight and defined stamping area (see experimental section for description) after production, thus correlates with the curing rate. At the same time, the PUR / PIR rigid foams also exhibit very good storage stability and foam properties, improved flame retardancy, and exhibit few defects in the produced panels. The PUR / PIR rigid foams according to the invention also exhibit advantages in their water absorption properties. The PUR / PIR rigid foam according to the invention can therefore be advantageously used as insulation foam in the production of composite elements. The invention also relates to a composite element comprising a rigid foam layer containing a PUR / PIR rigid foam according to the invention, and at least one cover layer. The cover layer is at least partially contacted by a layer comprising the PUR / PIR rigid foam according to the invention. The material of the cover layer is typically aluminum, steel, bitumen, paper, a mineral nonwoven, a nonwoven comprising organic fibers, a plastic plate, a plastic film, and / or a wood plate. In another embodiment of the composite element, this is in the form of an insulation panel. Experimental part: Methods used: Mold temperature: Temperature in °C of the mold used for foaming. Mixing time: the time in seconds during which the reaction mixture is mixed. Start time: the time in seconds that elapses from the start of mixing until the reaction is detected. Setting time: the time in seconds that elapses from the start of mixing until the foam surface solidifies. Tack-free time: the time in seconds that elapses from the start of mixing until the foam surface no longer feels tacky. Indentation depth (after a certain time): The indentation depth is measured on freshly produced laboratory foams in test packages with a base area of ​​20x20 cm 2 The penetration depth of a 3.5 cm diameter stamp weighing 6 kg is determined after the specified time periods during the curing phase. Cell size: Scale between 1 and 6, where 1 means very fine or very uniform and 6 means very coarse or irregular Surface / foam inner surface: qualitative distinction between brittle, sandy and tough Core density: DIN EN ISO 845:2009 “Foams made of rubber and plastics - Determination of bulk density” Isocyanate content: DIN EN 1242:2013 “Determination of isocyanate content” Viscosity: DIN 53019-1:2008 "Viscometry - Measurement of viscosity and flow curves using rotational viscometers." The measurement was performed without solvent. Hydroxyl number (OH number): the OH number was determined according to the provisions of DIN 53240-2:2007. Dimensional stability (Dim. Stab.): The foam sample is stored for at least 24 hours at 20-25 °C, before two foam cubes with the dimensions 10 • 10 • 10 cm are cut from the core. 3After marking the three spatial directions of each cube, they were measured with a caliper and stored at -22 °C and 100 °C for 24 hours. The cubes were then measured again at room temperature. The dimensional stability is the percentage Change in edge length AL in all three spatial directions A, B, and C, where C always corresponds to the foaming direction. AL = (L - OL) / OL • 100%, where L = edge length of the test specimen after storage, OL = edge length of the test specimen before storage. A foam passes this test if the change in any direction is less than 1% at -22 °C and 100 °C. Water absorption: A cube measuring 90 mm x 90 mm x 60 mm is weighed and immersed in a desiccator, then vacuumed to 100 mbar for 60 seconds. Excess water is then drained off, and the water absorption is determined by weighing. Swiss fire test: Test according to fire protection guideline no. 585.113 of the Association of Cantonal Life Insurance Companies VKL (SAR 585.113; Switzerland; as of March 23, 2015; Appendix 5 to the Fire Protection Ordinance). KBT : (Small Burner Test) Flame retardant test according to DIN EN ISO 11925-2 (2020-07) for the classification of flame retardant properties Compression Strength: Compressive strength at 10% compression in the running direction according to DIN EN 826-01 (2013-05) Thermal conductivity: Thermal conductivity according to DIN EN 12667-01 (2001-05) (at 10 °C or 70 °C, 0-value); 0-value means that the measurement is taken directly after production without prior storage. The content of isocyanurate groups in ISOCYANATES 1, 2 and 3 is determined according to the following equation: Isocyanurate% (ISOCYANATE 1, 2 or 3) = (NCO% (feedstock) -NCO% (ISOCYANATE 1, 2 or 3)) / (NCO% (feedstock) / 2) * 100; where NCO% (feedstock) is the NCO content of the polyisocyanate Al used (MDI200 or MDI 100). Storage test: The storage stability of the isocyanates was qualitatively assessed by storing the samples in the laboratory at room temperature for a period of 3 months and visually assessing them. GPC Gel Permeation Chromatography: The content of the various species was determined using gel permeation chromatography (GPC) according to DIN 55672-1:2016-03 at 35 °C in tetrahydrofuran as solvent (SECurity GPC system from PSS Polymer Service, flow rate 0.6 ml / min; columns: 2xPSS SDV 50A 5pm, 2xPSS SDV 100A 5pm, 8x300 mm; RI detector). Polystyrene standard samples with known molecular weight were used for calibration. The number-average molecular weight was calculated using the PSSWin GPC software. In the chromatogram, the peaks are named as shown in Figure 1. The peak with the seventh lowest molecular weight is designated "Peak G." Materials used: MDI100: Desmodur 44V10L, polymeric diphenylmethane diisocyanate (Covestro Deutschland AG); isocyanate content 31.8 wt.%, viscosity at 25°C approx. 100 mPas, MDI200: Desmodur 44V20L, polymeric diphenylmethane diisocyanate (Covestro Deutschland AG); isocyanate content 31.5 wt.%, viscosity at 25°C approx. 200 mPas MDI700: Desmodur 44V70L, polymeric diphenylmethane diisocyanate (Covestro Deutschland AG); isocyanate content 30.9 wt.%, viscosity at 25°C approx. 700 mPas, Benzoyl chloride: purchased from Sigma-Aldrich; 99.5%; boiling point 198 °C Tris(dimethylaminomethyl)phenol: purchased from Sigma-Aldrich, 95%; refractive index n20 / D 1.516, boiling point: 130-135 °C POLY OL 1 : aromatic polyester polyol (Synthesia Technology) with an OH number of 240 mg / kg KOH, a functionality calculated from the raw materials of 1.9 and a viscosity of 1500 mPa*s at 25 °C POLYOL 2: Polyetherdiol (Covestro) with an OH number of 28 mg / kg KOH and a viscosity of 860 mPa*s at 25°C, prepared with 1,2-propylene glycol as starter and a mixture of ethylene oxide and propylene oxide in a ratio of 30 to 70 parts by weight POLYOL 3: aromatic polyester polyol (Covestro) with an OH number of 370 mg / kg KOH, a functionality calculated from the raw materials of 1.9 and a viscosity of 1400 mPa*s at 25°C POLYOL 4: aromatic polyester polyol (Covestro) with an OH number of 795 mg / kg KOH, a functionality of 2.0 calculated from the raw materials and a viscosity of 1400 mPas at 25 °C POLYOL 5: aromatic polyester polyol (Stepan Company) with an OH number of 240 mg / kg KOH, an acid number of 0.8 and a viscosity of 3000 mPa*s at 25°C POLYOL 6: Polyetherdiol (Covestro) with an OH number of 35 mg / kg KOH and a viscosity of 860 mPa*s at 25°C, prepared with glycerol as starter and ethylene oxide and propylene oxide in a ratio of 13 to 87 parts by weight, with the ethylene oxide being added as a second block. Diethylene glycol: Diethylene glycol (Aldrich) Triethyl phosphate: flame retardant (Lanxess) Disflamol DPK: Flame retardant (Lanxess) Tegostab B8443: foam stabilizer (Evonik) DABCO LK443: Foam stabilizer (Evonik) Desmorapid 1792: potassium acetate catalyst (Covestro) Desmorapid DB: Benzyldimethylamine catalyst (Covestro) Desmorapid VP. PU1221 VN: Catalyst (Covestro) Desmorapid 1118: Catalyst (Covestro) Tetramethylguanidine: 1,1,3,3-tetramethylguanidine (Aldrich) n-pentane: n-pentane as a blowing agent (Aldrich) Cyclopentane: Cyclopentane as a blowing agent (Aldrich) Isopentane: Isopentane as a flatulent (Aldrich) ADHESIVE AGENT: 2K adhesion promoter (Covestro) TCPP: Fyrol PCF flame retardant (ICL) Tegostab B8421: Foam stabilizer (Evonik) Desmorapid PV: Pentamethyldiethyleneamine catalyst (Covestro) Kosmos 75 MEG: Potassium octoate catalyst (Biesterfeld) POLYOL MIXTURE 1: a mixture consisting of the following components: Example 1: Preparation of ISOCYANATE 1 (according to the invention) 99.80 parts by weight of MDI200 are placed under a blanket of dry nitrogen and heated to Heated to 60 °C. 0.17 parts by weight of tris(dimethylaminomethyl)phenol are added. The reaction temperature is kept constant at 60 + / - 2 °C. When the target viscosity of 700 mPas at 25 °C is reached, 0.03 parts by weight of benzoyl chloride are added and the mixture is heated for 20 minutes at 60 °C. Stirred. Viscosity, NCO content, and isocyanurate group content of ISOCYANATE 1: 678 mPas at 25°C; NCO content: 29.92% NCO; 10.0 wt.% isocyanurate groups. The GPC of ISOCYANATE 1 is shown in Figure 1, Table 1 shows the comparison of the peak areas and the number average molecular weights obtained from the gel permeation chromatograms of ISOCYANATE 1 and ISOCYANATE 2. Figure 1: RI signal of the gel permeation chromatogram of ISOCYANATE 1 with labeled peaks The area belonging to Peak G is 5.0%. The number average molecular weight Mn is 356 g / mol. Example 2a*: Preparation of ISOCYANATE 2 (comparison redilution, not according to the invention) 99.80 parts by weight of MDI200 are initially charged under a blanket of dry nitrogen and heated to 60 °C. 0.17 parts by weight of tris(dimethylaminomethyl)phenol are added. The reaction temperature is kept constant at 60 + / - 2 °C. When the target viscosity of 3000 mPas at 25 °C is reached, 0.03 parts by weight of benzoyl chloride are added and the mixture is stirred at 60 °C for 20 minutes. Viscosity of the intermediate product: 3360 mPas at 25 °C; NCO content of the intermediate product: 28.52% NCO. After the trimerization reaction has been terminated, 94.97 parts by weight of MDI200 are added to achieve the same viscosity and trimer content as in ISOCYANATE 1. The ISOCYANATE 2 obtained after mixing has a viscosity of 705 mPas at 25°C, a NCO content of 29.91%NCO and 10.0 wt.% isocyanurate groups. The area belonging to Peak G is 4.4%. The number average molecular weight Mn is 346 g / mol. Example 2b*: Preparation of ISOCYANATE 3 (comparison lower viscosity, to DE 691 16 583 T2, not according to the invention) 99.80 parts by weight of MDI100 are initially charged under a blanket of dry nitrogen and heated to 60°C. 0.17 parts by weight of tris(dimethylaminomethyl)phenol are added. The reaction temperature is kept constant at 60 + / - 2°C. With an NCO drop of approximately 1.5% NCO (corresponding to approximately 10% by weight of isocyanurate groups), 0.03 parts by weight of benzoyl chloride are added and the mixture is stirred at 60°C for 20 minutes. Viscosity, NCO content, and isocyanurate group content of ISOCYANATE 3: 355 mPas at 25°C; NCO content: 29.98% NCO; 11.4% by weight of isocyanurate groups. Example 2c* : Preparation of ISOCYANATE 4 (Comparison with iminourea as catalyst, to DE 691 16 583 T2, not according to the invention) 99.80 parts by weight of MDI200 are initially charged under a blanket of dry nitrogen and heated to 60 °C. 0.17 parts by weight of tetramethylguanidine are added. The reaction temperature is kept constant at 60 + / - 2 °C. With an NCO drop of approximately 1.5% (corresponding to approximately 10% by weight of isocyanurate groups), 0.03 parts by weight of benzoyl chloride are added and the mixture is stirred at 60 °C for 20 minutes. The reaction did not stop after the addition of benzoyl chloride. The reaction mass was then cooled to room temperature. Again, the reaction did not stop but continued, resulting in a solid after 24 hours. Table 1: Comparison of peak areas and number average molecular weights obtained from gel permeation chromatograms of ISOCYANATE 1 and ISOCYANATE 2*. Examples 3 - 6: Production of PUR / PIR foams The resulting compositions ISOCYANATE 1 and 2, containing isocyanate and isocyanurate groups, are used to produce rigid PUR / PIR foams and compared with a standard polyisocyanate composition of similar viscosity that contains isocyanurate groups. In Table 2 below, inventive example 5 with the composition ISOCYANATE 1 containing isocyanate and isocyanurate groups is foamed with the same polyol formulation. Comparative examples Example 3* and Example 4* are foamed with the composition MDI700 containing only isocyanate groups. Comparative example Example 6* is foamed with the composition ISOCYANATE 2 containing isocyanate and isocyanurate groups. For better comparability, the isocyanate composition was exchanged in equal parts by weight, resulting in slight variations in the index. Table 2: Laboratory foaming The experiments show that the use of the composition ISOCYANAT 1 according to the invention containing isocyanate and isocyanurate groups enables the production of PUR / PIR rigid foams by replacing the conventional pMDI by weight (ie without adjusting the index), When comparing physical / mechanical properties and processing characteristics, the PUR / PIR rigid foams are not inferior to those produced from conventional pMDI and are significantly superior in terms of indentation depth after 2.5 minutes and 5 minutes (Example 5). Non-inventive Example 6* shows that dilution from a very high-viscosity trimerized pMDI (viscosity greater than 2000 mPas at 25 °C before dilution, see preparation of ISOCYANATE 2) to a composition containing isocyanate and isocyanurate groups of approximately 700 mPas (ISOCYANATE 2) offers the same advantages in terms of indentation depth after 2.5 minutes and 5 minutes, but the PUR / PIR rigid foam does not exhibit such good properties in the fire test. Examples 7 - 9: Production of composite elements with steel facing on double belt Industrial-scale tests were conducted with the isocyanate components ISOCYANATE 1, ISOCYANATE 2, and MDI700 on a double conveyor belt with a steel cover layer (so-called metal panel; Table 3). The test conditions, feedstocks, and results are summarized in Table 3. The results show that the use of the inventive composition ISOCYANATE 1, containing isocyanate and isocyanurate groups, enables the production of composite elements with PUR / PIR rigid foams by replacing the conventional pMDI by weight (i.e., without adjusting the index), with comparable physical / mechanical properties and processing characteristics (Example 8). Non-inventive Example 9* shows that the use of a dilution of a very high-viscosity trimerized pMDI (viscosity greater than 2000 mPas at 25 °C before dilution, see preparation of ISOCYANATE 2) to a composition containing isocyanate and isocyanurate groups of approximately 700 mPas (ISOCYANATE 2) results in the same mechanical properties, but leads to undesirable defects on the underside of the sheet and does not perform as well in the fire test. Table 3 : Composite elements with steel cover layer on the double band - TI - The industrial-scale tests on a double conveyor belt with an aluminum cover layer (so-called insulation boards; Table 4) show that the use of the inventive composition ISOCYANAT 1 containing isocyanate and isocyanurate groups enables the production of composite elements with PUR / PIR rigid foams by replacing the conventional pMDI by weight (i.e. without adjusting the index), with comparable physical / mechanical properties and processing properties (Example 11). Non-inventive Example 12* shows that when using a rediluted, but before rediluting very highly viscous trimerized pMDI (viscosity greater than 2000 mPas at 25 °C before dilution, see Preparation of ISOCYANAT 2), a composition containing isocyanate and isocyanurate groups of approx.700 mPas (ISOCYANATE 2) leads to the same mechanical properties, but to undesirable defects in the cover layer and the compression strength in Example 11 according to the invention is superior to both Comparative Example 10* with conventional pMDI and Comparative Example 12*. The laboratory-scale tests (so-called insulation boards, Table 5) show that the use of the inventive composition ISOCYANATE 1, which contains isocyanate and isocyanurate groups, exhibits advantages in indentation depth after 3 minutes and 5 minutes as well as in water absorption (Example 13) compared to the non-inventive ISOCYANATE 3 (comparison with DE 691 16 583 T2, Example 14*). This is due to the high content of monomeric diphenylmethane diisocyanate. The MDI 100 used here is similar to the isocyanate used as a feedstock in DE 691 16 583 T2. In Comparative Example 14*, the use of MDI 100 results in the low functionality of the non-inventive ISOCYANATE 3. In summary, it can be stated that the use of the composition ISOCYANAT 1 according to the invention containing isocyanate and isocyanurate groups, compared to the conventional MDI700 and the non-inventive composition ISOCYANAT 2 containing isocyanurate groups, results in advantages with regard to the stackability of the foam sheets and the initial strength measured as indentation depth after 2.5 minutes and 5 minutes, with regard to the quality of the composite elements (in particular the surfaces) and in flame retardancy. Table 4: Foaming on the double conveyor belt with aluminum cover layers Table 5: Laboratory foaming

Claims

Process for the preparation of a composition A2 containing isocyanate and isocyanurate groups, comprising the steps: 1) Allowing a polyisocyanate Al to react in the presence of a trimerization catalyst and 2) stopping the reaction from step 1) using a suitable stopper to obtain composition A2; wherein the trimerization catalyst is not an iminourea, a derivative of an iminourea or a radical initiator and the concentration of the trimerization catalyst used is < 0.50 wt.% based on Al, and wherein the polyisocyanate Al used in step 1) is polymeric MDI with a monomeric diphenylmethane diisocyanate content of < 55 wt.% and a viscosity of 130 to 400 mPa*s, preferably 140 to 400 mPa*s at 25 °C (determined according to DIN 53019-1:2008-09, without solvent), and wherein step 2) is carried out when the reaction mixture from step 1) has 5 - <13 wt.% isocyanurate groups and its viscosity is < 2000 mPa*s at 25 °C (determined according to DIN 53019-1:2008-09, without solvent). Process according to claim 1, wherein the polyisocyanate used is Al < 50 wt.-% monomeric MDI and / or a viscosity of 140 to 300 mPa*s at 25 °C (determined according to DIN 53019-1:2008-09, without solvent). Process according to claim 1, wherein the stopper is a compound selected from acid chlorides or Bronsted acids, with the proviso that it is not sulfonic acid, sulfuric acid, or derivatives of these acids. Composition A2 containing isocyanate and isocyanurate groups, obtainable by a process according to one of claims 1 to 3. Composition A2 according to claim 4, characterized in that it has a seventh peak in GPC belonging to the traction with the seventh lowest molecular weight, the peak area of ​​which is > 4.6 area%. Composition A2 according to one of claims 4 or 5 which has a number-average molecular weight Mn of > 350 g / mol. Composition A2 according to one of claims 4 to 6, characterized in that it. a viscosity of < 1000 mPa*s at 25 °C (determined according to DIN 53019-1:2008-09, without solvent). An isocyanate component A comprising a composition A2 according to any one of claims 4 to 7. PUR / PIR system for producing a PUR / PIR rigid foam from an isocyanate component A according to claim 8 and a polyol formulation B in the presence of blowing agents C and optionally catalysts D as well as auxiliaries and additives E. PUR / PIR system according to claim 9, characterized in that the isocyanate number of the foam is > 250 to < 450, preferably > 320 to < 400. Process for producing a PUR / PIR rigid foam by reacting a PUR / PIR system according to claim 9 or 10. PUR / PIR rigid foam obtainable by a process according to claim 11. Use of a PUR / PIR rigid foam according to claim 12 as insulation foam in the production of composite elements.A composite element comprising a rigid foam layer containing a PUR / PIR rigid foam according to claim 12, and at least one cover layer. A composite element according to claim 14, wherein the material of the cover layer is aluminum, steel, bitumen, paper, a mineral nonwoven, a nonwoven comprising organic fibers, a plastic plate, a plastic film, and / or a wood plate.

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