Polyisocyanate mixtures

Abstract

The invention relates to a polyisocyanate mixture containing at least one polyisocyanurate-polyisocyanate and at least one polyallophanate-polyisocyanate, the monomeric diisocyanate content of the polyisocyanate mixture, determined according to DIN EN ISO 10283: 2007-11 by gas chromatography using an internal standard, being lt, and the monomeric diisocyanate content of the polyisocyanate mixture, determined according to DIN EN ISO 10283: 2007-11 by gas chromatography using an internal standard. The present invention relates to a polyisocyanate mixture comprising, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, 0.10% by weight, an isocyanurate group content of > = 40 mol% to < = 85 mol%, determined by NMR spectroscopy, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, and an allophanate group content of > = 15 mol% to < = 60 mol%, determined by NMR spectroscopy, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture.

Description

[0001] The invention relates to polyisocyanate mixtures and their use. Further subjects of the invention are coating compositions comprising the polyisocyanate mixtures, a process for producing a coating on a substrate, a coating obtainable by this process and a coated substrate.

[0002] High-quality light-resistant coatings are made in particular of coatings composed of aliphatic polyisocyanates and polyols, such as polyacrylate polyols, polyester polyols or polycarbonate polyols. The polyisocyanates used in these high-quality coatings include in particular derivatives made from hexamethylene 1,6-diisocyanate (HDI).

[0003] In particular, with the increasing demands on the resistance of coating systems, such as weathering and chemical resistance as well as high abrasion resistance, gloss retention and light fastness, systems with a relatively high OH group content are required in adhesives. Due to their chemical composition, such systems have an increased polarity compared to standard adhesives.

[0004] EP 0 277 353 A1 describes polyisocyanates having a biuret structure which are said to have good compatibility. However, the monomer stability of biuret-containing polyisocyanates may be reduced.

[0005] In these applications, polyisocyanurates are preferably used as crosslinkers, since, due to their lower viscosity, high-solids, VOC-compliant coating systems can be formulated. Such polyisocyanurates are described in DE-A 28 39 133. However, their compatibility in coating systems is generally lower than that of biuret-containing polyisocyanurates.

[0006] As an alternative to pure polyisocyanurates, WO 2019 / 061019 A1 describes polyisocyanate crosslinkers with a high allophanate group content, which are prepared in the presence of alcohols during a catalytic trimerization process. However, a disadvantage of these crosslinkers is their high viscosity.

[0007] Therefore, there is still a need to provide a polyisocyanate mixture which exhibits high chemical resistance as well as long processing times and good incorporation properties and good appearance of the resulting coating.

[0008] It was therefore an object of the present invention to provide polyisocyanate mixtures which exhibit high chemical resistance as well as long processing times and good incorporation properties and good appearance of the resulting coatings.

[0009] According to the invention, this object is achieved by a polyisocyanate mixture containing at least one polyisocyanurate-polyisocyanate and at least one polyalophanate-polyisocyanate, wherein the polyisocyanate mixture

[0010] The monomeric diisocyanate content, determined by gas chromatography using an internal standard according to DIN EN ISO 10283:2007-11, is <0.10% by weight.

[0011] an isocyanurate group content of ≥40 mol % to ≤85 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, determined by NMR spectroscopy, and

[0012] The allophanate group content determined by NMR spectroscopy is ≧15 mol % to ≦60 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture.

[0013] According to the invention, the term "comprising" or "containing" is preferably understood as "consisting essentially of", particularly preferably "consisting of. . . . The further embodiments described in the claims and the description can be combined arbitrarily, as long as the context does not clearly indicate otherwise.

[0014] The polyisocyanate mixtures according to the invention are physical mixtures and therefore differ from purely chemically prepared polyisocyanates, for example, with regard to their oligomer distribution, since the polyisocyanate mixtures according to the invention do not have a random distribution of the allophanate and isocyanurate groups throughout the polyisocyanate oligomers.

[0015] The at least one polyisocyanurate-polyisocyanate may contain other structural units, if any, only in minor amounts, such as uretdione structures and allophanate structures, wherein the isocyanurate structures constitute in each case the majority, preferably more than 80 mol %, particularly preferably more than 90 mol %, determined by NMR spectroscopy, based on the total amount of isocyanurate groups, allophanate groups and optionally other oligomeric structures of the polyisocyanurate-polyisocyanate. Also useful according to the invention as polyisocyanurate-polyisocyanates are isocyanurate-iminooxadiazinedione polyisocyanates, whose content of iminooxadiazinedione structures (so-called asymmetric trimers) is from 5 to 20 mol % and whose isocyanurate content is at least 50 mol %, determined by NMR spectroscopy, based on the total amount of isocyanurate groups, iminooxadiazinedione groups, allophanate groups and optionally other oligomeric structures of the polyisocyanurate-polyisocyanate. Such isocyanurate-iminooxadiazinedione polyisocyanates are also referred to in the present case as polyisocyanurate-polyisocyanates.

[0016] The at least one polyalophanate-polyisocyanate may also contain other structural units (if any, only in minor amounts), for example uretdione structures, iminooxadiazinedione structures (so-called asymmetric trimers) and isocyanurate structures, with the allophanate structures being in the majority in each case. However, according to the invention, it is also possible to use allophanate-isocyanurate mixed products whose allophanate content is at least 50 mol %, determined by NMR spectroscopy and based on the total amount of isocyanurate groups, iminooxadiazinedione groups, allophanate groups and optionally other oligomeric structures of the polyalophanate-polyisocyanate. Such allophanate-isocyanurate mixed products are also referred to in the present case as polyalophanate-polyisocyanates.

[0017] The content (mol %) of isocyanurate and allophanate structures present in the polyisocyanate mixture according to the invention or in the individual polyisocyanates used in the mixture is preferably determined by proton decoupling. 13 The integral of the C-NMR spectra was calculated and in each case based on the sum of the isocyanurate and allophanate structures present. This was done using a Bruker AV III HD600 NMR spectrometer with a Z150361_001 (CP BBO 600SS3 BB-H&F-05ZE T) sample head at 512 scans. With a repetition time (D1) of 4 s and a measurement time (AQ) of 1.57 s, it is assumed according to the invention that very similar carbonyl carbon atoms can be compared by integration. For polyisocyanates based on hexamethylene diisocyanate dissolved in CDCl3, the individual structural units have the following chemical shifts (in ppm): isocyanurate: 148.4; iminooxadiazinedione: 147.8, 144.3 and 135.3; allophanate: 155.7 and 153.8. For polyisocyanates based on hexamethylene diisocyanate dissolved in CDCl3, the chemical shifts (in ppm) of the structural units optionally present in minor amounts are as follows: uretdione: 157.1; biuret: 155.5; carbamate: 156.3; oxadiazinetrione: 147.8 and 143.9; uretonimine: 158.7 and 144.6.

[0018] In the context of the present invention, the weight-average molecular weight of the polyisocyanate mixture and of the individual polyisocyanates used in the mixture is determined by gel permeation chromatography in accordance with DIN EN ISO 13885-1:2021-11 using polystyrene standards.

[0019] The content of monomeric diisocyanates was determined in accordance with DIN EN ISO 10283:2007-11 by gas chromatography using an internal standard.

[0020] In the context of the present invention, pot life (hereinafter also referred to as "pot life") is defined as the time required for the viscosity of the coating composition to double (determined indirectly by doubling of the flow time in a 4 mm DIN cup).

[0021] An "organic compound" or "organic group" contains at least one unit comprising a covalent carbon-hydrogen bond.

[0022] The term "aliphatic" is defined herein as a saturated or unsaturated non-aromatic hydrocarbon group.

[0023] The term "araliphatic" is defined herein as a hydrocarbon group consisting of an aromatic hydrocarbon group and a saturated or unsaturated hydrocarbon group directly bonded to the aromatic group.

[0024] The term "cycloaliphatic" or "alicyclic" is defined herein as non-aromatic optionally substituted carbocyclic or heterocyclic compounds or units.

[0025] As used herein, "at least one" refers to one or more, for example 2, 3, 4, 5, 6, 7, 8, 9 or more. For the composition of the compounds described herein, the data do not refer to the absolute number of molecules, but to the type of composition. Therefore, "at least one polyalophanate-polyisocyanate" should be understood, for example, to include only one type of compound or a plurality of different types of such compounds, rather than giving the number of the various compounds.

[0026] Numerical ranges given in the format "from x to y" include the values ​​stated. If multiple preferred numerical ranges are given in this format, of course all ranges resulting from combinations of the various endpoints are also contemplated.

[0027] In a first preferred embodiment, the polyisocyanate mixture according to the invention has an isocyanurate group content of ≥45 mol % to ≤80 mol %, preferably ≥50 mol % to ≤75 mol %, particularly preferably ≥53 mol % to ≤72 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, as determined by NMR spectroscopy, and / or an allophanate group content of ≥20 mol % to ≤55 mol %, preferably ≥25 mol % to ≤50 mol %, particularly preferably ≥28 mol % to ≤47 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, as determined by NMR spectroscopy. This leads to the advantage of achieving a further extended pot life and at least unchanged good compatibility in coating systems.

[0028] In another preferred embodiment, the weight average molecular weight of the polyisocyanate mixture according to the invention, determined according to EN ISO 13885-1:2021-11, is ≥1000 g / mol to ≤3000 g / mol, preferably ≥1300 g / mol to ≤2700 g / mol, particularly preferably ≥1500 g / mol to ≤2500 g / mol. This leads to the further advantage of achieving good chemical resistance and further improved pot life.

[0029] In another preferred embodiment, the polydispersity of the polyisocyanate mixture according to the invention, determined according to DIN 55672-1:2016-03, is ≥1.5 to ≤2.5, preferably ≥1.7 to ≤2.2. This also leads to the further advantage of achieving good chemical resistance and a further improved pot life, which can be further increased when the two aforementioned preferred embodiments are combined.

[0030] Suitable starting compounds for the preparation of polyisocyanurate-polyisocyanates and polyalophanate-polyisocyanates suitable for producing the polyisocyanate mixtures according to the invention include any monomeric diisocyanates with aliphatic, cycloaliphatic, araliphatic and / or aromatically bound isocyanate groups, which can be prepared by any process, for example by phosgenation or by a phosgene-free route, for example by urethane cleavage.

[0031] Suitable monomeric diisocyanates (hereinafter also referred to as starting diisocyanates) include, for example, those having a molecular weight range of 168 to 400 g / mol, such as 1,6-diisocyanatohexane (HDI), 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,9-diisocyanatononane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatodecane. Isocyanatocyclohexane, 1,4-diisocyanato-3,3,5-trimethylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, 1,3-diisocyanato-4-methylcyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; IPDI), 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4'- and 4,4'-diisocyanatodicyclohexylmethane (H 12-MDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-3,3',5,5'-tetramethyldicyclohexylmethane, 4,4'-diisocyanato-1,1'-bis(cyclohexyl), 4,4'-diisocyanato-3,3'-dimethyl-1,1'-bis(cyclohexyl), 4,4'-diisocyanato-2,2',5,5'-tetramethyl-1,1'-bis(cyclohexyl)ester, 1,8-diisocyanato-p-menthane, 1,3-diisocyanato Suitable diisocyanates include 1,3-dimethyl-5,7-diisocyanatoadamantane, 1,3- and 1,4-bis(isocyanatomethyl)benzene (XDI), 1,3- and 1,4-bis(1-isocyanato-1-methylethyl)benzene (TMXDI), bis(4-(1-isocyanato-1-methylethyl)phenyl) carbonate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-toluene diisocyanate and any mixtures of these isomers, diphenylmethane 2,4′- and / or 4,4′-diisocyanate and naphthalene-1,5-diisocyanate and any mixtures of these diisocyanates. Other diisocyanates that are also suitable can be found, for example, in Justus Liebigs Annalen der Chemie, 562, 1949, 75-136.

[0032] Particularly preferred starting diisocyanates include linear or branched, aliphatic or alicyclic diisocyanates of the above-mentioned type. Very particularly preferred starting diisocyanates include 1,6-diisocyanatohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 2,4'- and / or 4,4'-diisocyanatodicyclohexylmethane, 1,3- and 1,4-bis-(isocyanatomethyl)benzene or any mixtures of these diisocyanates. 1,6-diisocyanatohexane (HDI) is particularly suitable.

[0033] The starting diisocyanate can be converted into polyisocyanurate-polyisocyanate and / or polyalophanate-polyisocyanate by various modification methods known per se. These polyisocyanurate-polyisocyanates and polyalophanate-polyisocyanates are mixed to obtain a polyisocyanate mixture according to the present invention. It can be adopted that those skilled in the art can refer to each polyisocyanate characteristic value, for example, the molar content of isocyanurate or allophanate groups determined by NMR spectroscopy, or if preferred, any mixing ratio selected effortlessly using polystyrene standards to measure weight-average molecular weight according to the above-mentioned DIN EN ISO 13885-1:2021-11.

[0034] In a further preferred embodiment, the at least one polyisocyanurate-polyisocyanate comprises one or more isocyanurate groups which are each chemically bonded together via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of ≥56 to ≤316 g / mol, preferably each via a 1,4-butyl or 1,6-hexyl group, particularly preferably each via a 1,6-hexyl group.

[0035] In the present invention, 1,4-butyl or 1,6-hexyl is understood to mean that the 1 and 4 positions or the 1 and 6 positions lack one hydrogen atom, respectively, and the group is chemically bonded through these atoms. "1,4-butyl or 1,6-hexyl" may also be referred to as "1,4-butanediyl" or "1,6-hexanediyl" in the present invention.

[0036] A preferred modification reaction of polyisocyanurate-polyisocyanates for preparing the polyisocyanate mixtures according to the invention is, for example, the catalytic trimerization of the starting diisocyanates. In principle, usable catalysts include all compounds which accelerate the trimerization of isocyanate groups to isocyanurate structures.

[0037] Suitable catalysts for preparing polyisocyanurate-polyisocyanates are, for example, simple tertiary amines, such as triethylamine, tributylamine, N,N-dimethylaniline, N-ethylpiperidine, N,N'-dimethylpiperazine, or tertiary phosphines, such as triethylphosphine, tributylphosphine or dimethylphenylphosphine. Suitable catalysts also include the tertiary hydroxyalkylamines described in GB 2221465, such as triethanolamine, N-methyldiethanolamine, dimethylethanolamine, N-isopropyldiethanolamine and 1-(2-hydroxyethyl)pyrrolidine, or the catalyst system known from GB 2222161, which consists of a mixture of a tertiary bicyclic amine (e.g. DBU) and a simple low molecular weight aliphatic alcohol.

[0038] A wide variety of metal compounds are likewise suitable as trimerization catalysts. Suitable examples include the octoates and naphthenates of manganese, iron, cobalt, nickel, copper, zinc, zirconium, cerium or lead described as catalysts in DE-A 3240613, or mixtures thereof with acetates of lithium, sodium, potassium, calcium or barium, the sodium and potassium salts of linear or branched alkanecarboxylic acids having up to 10 carbon atoms, for example the sodium and potassium salts of propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid and undecanoic acid, disclosed in DE-A 3219608, the alkali metal or alkaline earth metal salts of aliphatic, alicyclic or aromatic mono- and polycarboxylic acids having 2 to 20 carbon atoms, for example sodium or potassium benzoate, disclosed in EP-A 0100129, the alkali metal phenates, for example sodium or potassium phenate, disclosed in GB 1391066 A and GB 1386399 A, GB 809809 disclosed in the United States Patent No. 809809, alkali metal salts of enolate compounds, and metal salts of weak aliphatic or alicyclic carboxylic acids, such as sodium methoxide, sodium acetate, sodium acetate, sodium acetoacetate, lead 2-ethylhexanoate and lead naphthenate, basic alkali metal compounds complexed with crown ethers or polyether alcohols, such as complexed sodium or potassium carboxylates, as disclosed in EP-A 0056158 and EP-A 0056159, potassium pyrrolidone as disclosed in EP-A 0033581, mononuclear or polynuclear complexes of titanium, zirconium and / or hafnium, such as zirconium tetra-n-butoxide, zirconium tetra-2-ethylhexanoate and zirconium tetra-2-ethylhexoxide, as disclosed in EP-A 2883895, and European Tin compounds of the type described in Polymer Journal, 16, 1979, 147-148, for example, dibutyltin dichloride, diphenyltin dichloride, triphenyltin alcohol, tributyltin acetate, tributyltin oxide, tin octoate, dibutyl(dimethoxy)stannane and tributyltin imidazolate.

[0039] Other trimerization catalysts suitable for preparing polyisocyanurate-polyisocyanates are, for example, the quaternary ammonium hydroxides disclosed in DE-A 1667309, EP-A 0013880 and EP-A 0047452, for example tetraethylammonium hydroxide, trimethylbenzylammonium hydroxide, N,N-dimethyl-N-dodecyl-N-(2-hydroxyethyl)ammonium hydroxide, N-(2-hydroxyethyl)-N,N-dimethyl-N-(2,2'-dihydroxymethylbutyl)ammonium hydroxide and 1-(2-hydroxyethyl)-1,4-diazabicyclo[2.2.2]octane hydroxide (monoadduct of ethylene oxide and water on 1,4-diazabicyclo[2.2.2]octane), the quaternary hydroxyalkylammonium hydroxides disclosed in EP-A 3765 or EP-A 10589, for example N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium hydroxide; 4,789,705, for example N,N,N-trimethyl-N-2-hydroxypropylammonium p-tert-butylbenzoate and N,N,N-trimethyl-N-2-hydroxypropylammonium 2-ethylhexanoate; quaternary benzylammonium carboxylates disclosed in EP-A 1 229 016, for example N-benzyl-N,N-dimethyl-N-ethylammonium pivalate, N-benzyl-N,N-dimethyl-N-ethylammonium 2-ethylhexanoate, N-benzyl-N,N,N-tributylammonium 2-ethylhexanoate, N,N-dimethyl-N-ethyl-N-(4-methoxybenzyl)ammonium 2-ethylhexanoate or N,N,N-tributylammonium pivalate, WO 2631 733, EP-A 0 671 426, EP-A 1 599 526 and U.S. Pat. No. 4,789,705; quaternary benzylammonium carboxylates disclosed in EP-A 1 229 016, for example N-benzyl-N,N-dimethyl-N-ethylammonium pivalate, N-benzyl-N,N-dimethyl-N-ethylammonium 2-ethylhexanoate, N-benzyl-N,N,N-tributylammonium 2-ethylhexanoate, N,N-dimethyl-N-ethyl-N-(4-methoxybenzyl)ammonium 2-ethylhexanoate or N,N,N-tributylammonium (4-methoxybenzyl)ammonium pivalate, WO 2631 733, EP-A 0 671 426, EP-A 1 599 526 and U.S. Pat. The tetrasubstituted α-hydroxyammonium carboxylates disclosed in 2005 / 087828, such as tetramethylammonium lactate, the quaternary ammonium or phosphonium fluorides disclosed in EP-A 0339396, EP-A 0379914 and EP-A 0443167, such as C8-C 10alkyl N-methyl-N,N,N-trialkylammonium fluorides, N,N,N,N-tetra-n-butylammonium fluoride, N,N,N-trimethyl-N-benzylammonium fluoride, tetramethylphosphonium fluoride, tetraethylphosphonium fluoride or tetra-n-butylphosphonium fluoride, quaternary ammonium and phosphonium polyfluorides disclosed in EP-A 0798299, EP-A 0896009 and EP-A 0962455, for example benzyltrimethylammonium hydrogen polyfluoride, tetraalkylammonium alkyl carbonates disclosed in EP-A 0668271, which can be obtained by reaction of tertiary amines with dialkyl carbonates, or quaternary ammonium alkyl carbonates of betaine structure, quaternary ammonium hydrogen carbonates disclosed in WO 1999 / 023128, for example choline hydrogen carbonate, EP-A 0798299, EP-A 0896009 and EP-A 0962455, for example benzyltrimethylammonium hydrogen polyfluoride, Quaternary ammonium salts obtainable from tertiary amines and alkylating esters of phosphoric acid disclosed in WO 20102482, for example, the reaction product of triethylamine, DABCO or N-methylmorpholine with dimethyl methanephosphonate, or tetrasubstituted ammonium salts of lactams disclosed in WO 2013 / 167404, for example, trioctylammonium caprolactam or dodecyltrimethylammonium caprolactam.

[0040] These catalysts can be used alone or in any mixture with one another. Preferred catalysts are ammonium salts and phosphonium salts of the above-mentioned type, in particular trialkylhydroxyalkylammonium carboxylates, benzylammonium carboxylates, quaternary ammonium hydroxides, hydroxyalkylammonium hydroxides, ammonium or phosphonium fluorides and ammonium and phosphonium polyfluorides of the above-mentioned type. Particularly preferred trimerization catalysts are quaternary ammonium hydroxides and ammonium and phosphonium polyfluorides of the above-mentioned type.

[0041] In the preparation of the polyisocyanurate-polyisocyanates of the polyisocyanate mixtures according to the invention, trimerization catalysts are generally used in concentrations of 0.0005 to 5.0% by weight, preferably 0.0010 to 2.0% by weight, particularly preferably 0.0015 to 1.0% by weight, based on the amount of starting diisocyanate used.

[0042] The trimerization catalyst is preferably added to the starting diisocyanate in pure form. However, in order to improve its compatibility, the trimerization catalyst can also be used optionally in the form of a solution dissolved in a suitable organic solvent. The dilution of the catalyst solution can be freely selected within a wide range. Such catalyst solutions are usually catalytically active at a concentration of 0.01% by weight or more.

[0043] Suitable catalyst solvents are, for example, solvents which are inert toward isocyanate groups, such as hexane, toluene, xylene, chlorobenzene, ethyl acetate, butyl acetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, propylene glycol monomethyl ether acetate, 1-methoxy-2-propyl acetate, 3-methoxy-n-butyl acetate, propylene glycol diacetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, lactones such as β-propiolactone, γ-butyrolactone, ε-caprolactone and ε-methylcaprolactone, and solvents such as N-methylpyrrolidone and N-methylcaprolactam, 1,2-propylene carbonate, dichloromethane, dimethyl sulfoxide, triethyl phosphate or any mixtures of these solvents.

[0044] If a catalyst solvent is used in the preparation of a suitable polyisocyanurate-polyisocyanate, it is preferred to use a catalyst solvent which carries isocyanate-reactive groups and can be incorporated into the polyisocyanurate-polyisocyanate. Examples of such solvents include monohydric or polyhydric simple alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, isobutylene glycols, 2-ethylhexane-1,3-diol or glycerol; ether alcohols, such as 1-methoxy-2-propanol, 3-ethyl-3-hydroxymethyloxetane, tetrahydrofurfuryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol, dipropylene glycol or liquid high Molecular weight polyethylene glycols, polypropylene glycols, mixed polyethylene glycols / polypropylene glycols and their monoalkyl ethers; ester alcohols, for example ethylene glycol monoacetate, propylene glycol monolaurate, glycerol mono- and diacetates, glycerol monobutyrate or 2,2,4-trimethylpentane-1,3-diol monoisobutyrate; unsaturated alcohols, for example allyl alcohol, 1,1-dimethylallyl alcohol or oleyl alcohol; araliphatic alcohols, for example benzyl alcohol; N-monosubstituted amides, for example N-methylformamide, N-methylacetamide, cyanoacetamide or 2-pyrrolidone, or any mixtures of these solvents. In the case of the optional co-use of these catalytic solvents bearing isocyanate-reactive groups, the allophanate groups that may be formed thereby are also included in the molar content of allophanate groups according to the invention and in the total amount of isocyanurate and allophanate groups in the polyisocyanate mixture according to the invention.

[0045] According to the invention, the polyisocyanurate-polyisocyanate used can also be an isocyanurate-iminooxadiazinedione-polyisocyanate with an isocyanurate content of at least 50 mol %, which is also referred to as polyisocyanurate-polyisocyanate in the context of the present invention. Such iminooxadiazinedione groups (also referred to as asymmetric trimers) can be prepared, for example, by the methods described in EP-A 0798299, EP-A 0962454, WO 2015 / 124504 or WO 2017 / 029266.

[0046] The preparation of the polyisocyanurate-polyisocyanates used for the polyisocyanate mixtures according to the invention is carried out by methods known per se, for example those described in the publications mentioned above in the enumeration of suitable trimerization catalysts.

[0047] Typically, the abovementioned amounts of a suitable trimerization catalyst are added to the starting diisocyanate, optionally under an inert gas (e.g. nitrogen) and optionally in the presence of a solvent (e.g. the abovementioned possible catalyst solvents inert toward isocyanate groups) at a temperature of 0° C. to 150° C., preferably 20° C. to 130° C., particularly preferably 40° C. to 120° C., to initiate a trimerization reaction to form an isocyanurate structure.

[0048] As with all processes for the preparation of polyisocyanates for use according to the invention, the progress of the reaction can be monitored, for example, by titrimetric determination of the NCO content in accordance with DIN EN ISO 11909:2007-05.

[0049] The trimerization reaction is terminated after the desired degree of oligomerization has been reached, wherein the "degree of oligomerization" is understood to be the percentage of isocyanate groups originally present in the reaction mixture which are consumed during the preparation process to preferably form isocyanurate structures. Depending on the type of starting diisocyanate or starting diisocyanate mixture used, at least the desired degree of oligomerization may vary.

[0050] For example, the reaction can be terminated at the desired degree of oligomerization by cooling the reaction mixture to room temperature.However, the reaction is terminated by adding a catalyst poison and optionally subsequently briefly heating the reaction mixture to a temperature of, for example, above 80°C.

[0051] Such catalyst poisons include, for example, inorganic acids such as hydrochloric acid, phosphorous acid or phosphoric acid, acid chlorides such as acetyl chloride, benzoyl chloride or isophthaloyl chloride, sulfonic acids and sulfonic esters such as methanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, dodecylbenzenesulfonic acid, methyl and ethyl p-toluenesulfonate, monoalkyl and dialkyl phosphates such as monotridecyl phosphate, dibutyl phosphate and dioctyl phosphate, and silylated acids such as trimethylsilyl methanesulfonate, trimethylsilyl trifluoromethanesulfonate, tris(trimethylsilyl) phosphate and diethyl trimethylsilyl phosphate.

[0052] The amount of catalyst poison required to terminate the reaction depends on the amount of trimerization catalyst used. Generally, one equivalent of catalyst poison is used based on the catalyst initially used. However, if the catalyst loss that may occur during the reaction is taken into account, 20-80 equivalent % of catalyst poison based on the amount of catalyst initially used is sufficient to terminate the reaction.

[0053] The above-mentioned catalyst poison can be used in pure substance form or in the form of being dissolved in a suitable solvent. Suitable solvents include, for example, the solvents or mixtures thereof already described above as possible catalyst solvents. The dilution can be freely selected within a wide range, for example, solutions with a concentration of 1% or more are suitable.

[0054] In addition to the abovementioned solvents, it is also possible to use the abovementioned starting diisocyanates as solvents for the catalyst poison, provided that the latter are sufficiently inert toward isocyanate groups to allow the preparation of storage-stable solutions.

[0055] After completion of the reaction, the volatile components of the reaction mixture (e.g. excess starting diisocyanate and any co-used solvent) are removed, preferably under vacuum, by thin-film distillation, for example at a pressure of less than 1.0 mbar, preferably less than 0.5 mbar, particularly preferably less than 0.2 mbar and under conditions that are as mild as possible, for example at a temperature of 100° C. to 200° C., preferably 120° C. to 180° C.

[0056] The volatile constituents can likewise be separated off from the polyisocyanates by extraction with suitable solvents which are inert toward isocyanate groups, for example aliphatic or cycloaliphatic hydrocarbons, such as pentane, hexane, heptane, cyclopentane or cyclohexane.

[0057] The residual content of monomeric diisocyanates after distillation or extraction is preferably ≤0.50% by weight, particularly preferably ≤0.3% by weight, particularly preferably <0.10% by weight. The content of monomeric diisocyanates in the at least one polyisocyanurate-polyisocyanate may be greater than 0.10% by weight, provided that it is less than 0.10% by weight in the polyisocyanate mixture according to the invention.

[0058] In addition to the at least one polyisocyanurate-polyisocyanate, the polyisocyanate mixture according to the invention also comprises at least one polyallophanate-polyisocyanate, which is obtained, for example, by reaction of the starting diisocyanate with a hydroxy-functional compound.

[0059] In another preferred embodiment, the at least one polyalphonate-polyisocyanate comprises one or more allophanate groups, each of which is chemically bonded together via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of ≥56 to ≤316 g / mol, preferably each via a 1,4-butyl or 1,6-hexyl group, particularly preferably each via a 1,6-hexyl group.

[0060] In the present invention, 1,4-butyl or 1,6-hexyl is understood to mean that the 1 and 4 positions or the 1 and 6 positions lack one hydrogen atom, respectively, and the group is chemically bonded through these atoms. "1,4-butyl or 1,6-hexyl" may also be referred to as "1,4-butanediyl" or "1,6-hexanediyl" in the present invention.

[0061] When mixtures of different starting diisocyanates are used, it is very particularly preferred that ≤30% by weight, preferably ≤10% by weight, particularly preferably ≥0% by weight to ≤5% by weight of the total starting diisocyanates used are cycloaliphatic diisocyanates and the remainder are aliphatic diisocyanates.

[0062] Suitable hydroxy-functional compounds for preparing the polyalophanate-polyisocyanates of the polyisocyanate mixtures according to the invention include, for example, any mono- or polyols having up to 14 carbon atoms, preferably 2 to 6 carbon atoms, such as the mono- or polyols mentioned above as suitable hydroxy-functional catalyst solvents and also tetrahydrofurfuryl alcohol, the isomeric pentanediols, hexanediols, heptanediols and octanediols, 1,10-decanediol, 1,2- and 1,4-cyclohexanediols, 1, 4-Cyclohexanedimethanol, 4,4'-(1-methylethylidene)bicyclohexanol, 1,1,1-trimethylolethane, 1,2,6-hexanetriol, 1,1,1-trimethylolpropane, 2,2-bis(hydroxymethyl)-1,3-propanediol, bis(2-hydroxyethyl)hydroquinone, 1,2,4- and 1,3,5-trihydroxycyclohexane or 1,3,5-tris(2-hydroxyethyl)isocyanurate, and also simple ester alcohols such as neopentyl glycol hydroxypivalate.

[0063] Suitable hydroxy-functional compounds for preparing the polyalophanate-polyisocyanates also include higher molecular weight polyhydroxy compounds of the polyester, polycarbonate, polyester carbonate or polyether type known per se, in particular those having a molecular weight range of 200 to 2000 g / mol.

[0064] Suitable polyester polyols as hydroxy-functional compounds include, for example, those having an average molecular weight, which can be calculated from the functionality and the hydroxyl number, of 200 g / mol to 4000 g / mol, preferably 250 g / mol to 2500 g / mol, and a hydroxyl content of 1% to 21% by weight, preferably 2% to 18% by weight, which can be prepared, for example, by reacting polyols (for example the abovementioned polyols having 2 to 14 carbon atoms) with a deficient amount of polycarboxylic acids, the corresponding carboxylic anhydrides, the corresponding lower alcohol polycarboxylic acid esters or lactones.

[0065] The acid or acid derivative used to prepare the polyester polyol can be aliphatic, alicyclic and / or aromatic, and can optionally be substituted, for example, by halogen atoms, and / or unsaturated. Examples of suitable acids include, for example, polycarboxylic acids or derivatives thereof having a molecular weight range of 118 to 300 g / mol, such as succinic acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic acid, maleic acid, maleic anhydride, dimerized and trimerized fatty acids, dimethyl terephthalate and diethylene glycol terephthalate.

[0066] For the preparation of the polyester polyols, it is also possible to employ, for example, any desired mixtures of the starting compounds mentioned.

[0067] Alternatively used as hydroxy-functional compounds are polyester polyols which can be prepared in a known manner from lactones and simple polyols, such as those mentioned above as starter molecules by ring opening. Examples of suitable lactones for preparing these polyester polyols are β-propiolactone, γ-butyrolactone, δ- and δ-valerolactone, ε-caprolactone, 3,5,5- and 3,3,5-trimethylcaprolactone or any mixtures of these lactones.

[0068] Polyhydroxy compounds of the polycarbonate type suitable as hydroxy-functional compounds include in particular the polycarbonate diols known per se, which can be prepared, for example, by reaction of diols (such as those mentioned by way of example in the above list of polyols with a molecular weight range of 62 to 400 g / mol) with diaryl carbonates (for example diphenyl carbonate), dialkyl carbonates (for example dimethyl carbonate) or phosgene.

[0069] Suitable polyhydroxy compounds of the polyester carbonate type as hydroxy-functional compounds include, in particular, the diols known per se containing ester groups and carbonate groups, which are obtainable, for example, according to the teaching of DE-A 1770245 or WO 03 / 002630 by reacting diols with lactones of the type mentioned above by way of example, in particular ε-caprolactone, and subsequently reacting the resulting polyester diols with diphenyl carbonate or dimethyl carbonate.

[0070] Suitable polyether polyols for use as hydroxy-functional compounds include in particular those having an average molecular weight, calculated from the functionality and the hydroxyl number, of 200 to 2000 g / mol, preferably 250 to 1000 g / mol, and a hydroxyl content of 1.6 to 25% by weight, preferably 3.6 to 20% by weight, which can be obtained in a manner known per se by alkoxylation of suitable starter molecules. For the preparation of these polyether polyols, any polyols (for example the above-mentioned simple polyols having 2 to 14 carbon atoms) can be used as starter molecules. Alkylene oxides suitable for the alkoxylation reaction include in particular ethylene oxide and propylene oxide, which can be used for the alkoxylation reaction in any order or in the form of a mixture.

[0071] Suitable polyether polyols also include the polyoxytetramethylene glycols known per se, which are obtainable, for example, by polymerization of tetrahydrofuran according to H. Meerwein et al., Angew. Chem. 72, 1960, 927-934. However, the use of polyether polyols is not preferred.

[0072] Preferred hydroxy-functional compounds are the abovementioned simple polyols, ester alcohols or ether alcohols having a molecular weight range of 62 to 400 g / mol. Particular preference is given to the diols and / or triols having 2 to 6 carbon atoms mentioned in the abovementioned list of simple polyols. Very particularly preferred hydroxy-functional compounds are ethane-1,2-diol, propane-1,2-diol, propane-1,3-diol, butane-1,3-diol, butane-1,4-diol, hexane-1,6-diol and / or 1,1,1-trimethylolpropane. Particular preference is given to using 1,1,1-trimethylpropane.

[0073] In another preferred embodiment, the polyalophanate-polyisocyanate is obtained by oligomerizing at least one aliphatic, cycloaliphatic or araliphatic monomeric diisocyanate having a molecular weight of ≥140 to ≤400 g / mol with at least one hydroxy-functional compound having an OH functionality of ≥2 and ≤6 in the presence of a catalyst.

[0074] Preferably, the hydroxy-functional compound has an OH functionality of ≥3 and ≤5 and / or a molecular weight of ≥85 to ≤2000 g / mol, particularly preferably an OH functionality of ≥3 and ≤4 and / or a molecular weight of ≥130 to ≤500 g / mol. Mixtures of these alcohols can also be used.

[0075] Alternatively, the at least one polyalophanate-polyisocyanate is preferably obtained by oligomerization of at least one aliphatic, cycloaliphatic or araliphatic monomeric diisocyanate having a molecular weight of ≥140 to ≤400 g / mol and at least one hydroxy-functional compound having an OH functionality of ≥3 and ≤6. Mixtures of these alcohols can also be used.

[0076] The at least one polyalophanate-polyisocyanate is preferably obtained by oligomerization of at least one aliphatic diisocyanate having a molecular weight of ≥140 to ≤400 g / mol, preferably 1,6-diisocyanatohexane (HDI), with at least one hydroxy-functional compound having an OH functionality of ≥3 and ≤5 and / or a molecular weight of ≥85 to ≤2000 g / mol, preferably an OH functionality of ≥3 and ≤4 and / or a molecular weight of ≥130 to ≤500 g / mol. Mixtures of these alcohols can also be used.

[0077] The starting diisocyanate and the hydroxy-functional compound are preferably reacted in an equivalent ratio of isocyanate groups to hydroxyl groups of 4:1 to 200:1, preferably 5:1 to 50:1, particularly preferably 5:1 to 25:1, in the presence of at least one suitable catalyst of the type mentioned.

[0078] The reaction of preparing polyalophanate-polyisocyanate can be carried out as heat-induced allophanation without catalysis. However, it is preferred to use a suitable catalyst to accelerate the reaction. Suitable catalysts for the reaction include, for example, WO 2019 / 061019 A1, page 11, line 13 to the catalyst described in line 11 of page 13. The catalyst is added in pure form or in a form dissolved in a suitable organic solvent to accelerate the formation of allophanate groups. Preferred catalyst solvents are solvents having isocyanate-reactive groups and capable of being incorporated into polymers accordingly. These include, for example, mono- or polyols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, butanediol isomers, 2-ethylhexane-1,3-diol, glycerol, ether alcohols such as 1-methoxy-2-propanol, 3-ethyl-3-hydroxymethyloxetane, tetrahydrofurfuryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol, dipropylene glycol , polyethylene glycol, polypropylene glycol, mixed polyethylene glycol / polypropylene glycol and their monoalkyl ethers, ester alcohols such as ethylene glycol monoacetate, propylene glycol monolaurate, glycerol diacetate, glycerol monobutyrate or 2,2,4-trimethylpentane-1,3-diol monoisobutyrate, unsaturated alcohols such as allyl alcohol, 1,1-dimethylallyl alcohol or oleyl alcohol, aromatic aliphatic alcohols such as benzyl alcohol or monosubstituted amides such as N-methylformamide, N-methylacetamide, cyanoacetamide or 2-pyrrolidone or mixtures of these solvents.

[0079] The reaction is preferably carried out under an inert gas atmosphere at a temperature of 0°C to 150°C, preferably 40°C to 130°C, particularly preferably 70°C to 120°C.

[0080] After the desired conversion has been achieved, the reaction is stopped. This can be achieved, for example, by cooling the reaction mixture. Stopping is preferably achieved by adding a catalyst poison and optionally subsequently heating the reaction mixture to a temperature above 80°C.

[0081] Suitable catalyst poisons (inhibitors) are known to the person skilled in the art. For example, the catalyst poison is hydrochloric acid, phosphoric acid, phosphonic acid, carboxylic acid chlorides, for example acetyl chloride, benzoyl chloride or isophthaloyl chloride, sulfonic acids or sulfonic esters, for example methanesulfonates, p-toluenesulfonic acid, trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, dodecylbenzenesulfonic acid, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, monoalkyl or dialkyl phosphates, for example tridecyl phosphate, dibutyl phosphate, dioctyl phosphate, or silylated acids, for example trimethylsilyl methanesulfonate, trimethylsilyl trifluoromethanesulfonate, tris(trimethylsilyl) phosphate or diethyl(trimethylsilyl) phosphate.

[0082] The amount of catalyst poison required to stop the reaction depends primarily on the amount of catalyst used. In principle, one equivalent of inhibitor is required; however, since some catalysts are often deactivated in other ways, smaller amounts of inhibitor may also be sufficient.

[0083] The catalyst poison can also be added in pure form or in the form of a solution, wherein, for example, the catalyst solvents listed above are suitable as solvents. In addition to these solvents, the starting isocyanate can also be used as a solvent for the catalyst poison.

[0084] After the reaction has terminated, the starting diisocyanate is separated from the reaction product. This is preferably done by distillation, for example at a pressure of less than 5 mbar, preferably less than 1 mbar, particularly preferably less than 0.5 mbar and for example at a temperature of 100° C. to 200° C., preferably 120° C. to 180° C. The residual content of monomeric diisocyanates after distillation is preferably ≤0.50% by weight, particularly preferably ≤0.3% by weight, particularly preferably <0.10% by weight. The content of monomeric diisocyanates in the at least one polyalophanate-polyisocyanate may be greater than 0.10% as long as it is less than 0.10% by weight in the polyisocyanate mixture according to the invention.

[0085] Preferably, the polyalophanate-polyisocyanate has an average isocyanate functionality of ≥4 and / or a weight average molecular weight determined according to EN ISO 13885-1:2021-11 of ≥3000 g / mol.

[0086] In the present case, the average isocyanate functionality in the polyisocyanurate-polyisocyanate comprising at least one polyisocyanate is determined by the following formula:

[0087]

[0088] Therein, the isocyanate content is indicated in % by weight and is determined titrimetrically in accordance with DIN EN ISO 11909:2007-05, and the number-average molecular weight is determined by GPC in accordance with DIN EN ISO 13885-1:2021-11 using polystyrene as standard and tetrahydrofuran as eluent.

[0089] Another subject matter of the present invention is also a method for preparing the polyisocyanate mixture according to the invention, characterized in that at least one polyisocyanurate-polyisocyanate and at least one polyalophanate-polyisocyanate are mixed, wherein the weight-average molecular weight of the at least one polyisocyanurate-polyisocyanate determined according to DIN EN ISO 13885-1:2021-11 is preferably ≤1000 g / mol and / or the weight-average molecular weight of the at least one polyalophanate-polyisocyanate determined according to DIN EN ISO 13885-1:2021-11 is ≥3000 g / mol.

[0090] Mixing can be carried out by any method and in any order. If necessary, a suitable solvent can be added to the method. Suitable solvents include coating field solvents commonly known to those skilled in the art and are mentioned in this article by way of example.

[0091] In a preferred embodiment of the inventive method, at least one polyisocyanurate polyisocyanate of 30-70 weight portion and at least one polyalophanate-polyisocyanate of 70-30 weight portion are mixed. Here, one or more solvents described herein may be included in one and / or two polyisocyanates for mixing, preferably at least butyl acetate. When one or more solvents are used together, it is particularly preferred that polyalophanate-polyisocyanate is present in a solvent.

[0092] The present invention further provides a coating composition comprising at least one polyisocyanate mixture according to the invention and at least one binder reactive toward isocyanate groups, or at least one polyisocyanate mixture obtainable or produced according to a process according to claim 8 or 9 and at least one binder reactive toward isocyanate groups.

[0093] In a further preferred embodiment, the coating composition according to the invention comprises in component A) the at least one binder reactive toward isocyanate groups and in component B) the at least one polyisocyanate mixture according to the invention or in component B) the at least one polyisocyanate mixture obtainable or prepared by the process according to claim 8 or 9. This preferred embodiment is also referred to hereinafter as a two-component system.

[0094] Useful "binders reactive toward isocyanate groups" include all compounds known to the person skilled in the art whose average OH or NH functionality is at least 1.5. These compounds may include, for example, low molecular weight diols (e.g. ethane-1,2-diol, propane-1,3- or -1,2-diol, butane-1,4-diol), triols (e.g. glycerol, trimethylolpropane) and tetraols (e.g. pentaerythritol), short-chain polyamines, and polyhydroxy compounds such as polyether polyols, polyester polyols, polyurethane polyols, polysiloxane polyols, polycarbonate polyols, polyether polyamines, polybutadiene polyols, polyacrylate polyols and / or polymethacrylate polyols and copolymers thereof, hereinafter referred to as polyacrylate polyols.

[0095] Whether it is the coating composition of the invention or the preferred two-component system of the invention, it is further preferred that the at least one binder reactive toward isocyanate groups is a polyol, preferably a polyether polyol, a polyester polyol, a polyurethane polyol, a polysiloxane polyol, a polycarbonate polyol, a polyether polyamine, a polybutadiene polyol, a polyacrylate polyol and / or a polymethacrylate polyol or a copolymer thereof, particularly preferably a polycarbonate polyol, a polyester polyol, a polyacrylate polyol or any mixture thereof.

[0096] Both for the coating composition of the invention and for the preferred two-component system of the invention, it is further preferred that the at least one binder reactive toward isocyanate groups comprises at least one hydroxyl-functional compound having a hydroxyl content of ≥2.0% by weight, preferably ≥3.0% by weight, particularly preferably ≥3.5% by weight, based on the solids content of the binder reactive toward isocyanate groups.

[0097] Preferably, the ratio of the polyisocyanate mixture of the invention to the compound reactive toward isocyanate groups in the coating composition of the invention or the two-component system of the invention (based on the molar amount of isocyanate groups and NCO-reactive groups) is from 0.8:1.0 to 2.0:1.0. Particularly preferred ratios are from 1.0:1.0 to 1.5:1.0. Very particularly preferred ratios are from 1.05:1.0 to 1.25:1.0.

[0098] The mass average molecular weight Mw of the polyols, measured by gel permeation chromatography (GPC) against polystyrene standards, is preferably >500 Daltons, more preferably 800 to 100,000 Daltons, in particular 1,000 to 50,000 Daltons.

[0099] The OH value of the polyol is preferably 30 to 400 mg KOH / g, in particular 100 to 300 mg KOH / g. The hydroxyl value (OH value) indicates how many mg of potassium hydroxide are equivalent to the amount of acetic acid bound per 1 g of substance during the acetylation process. When determining, the sample is boiled with acetic anhydride / pyridine and the acid formed is titrated with potassium hydroxide solution (DIN 53240-2).

[0100] The glass transition temperature of the polyhydroxy compounds, determined by means of DSC measurement in accordance with DIN EN ISO 11357-2, is preferably from -150 to 100°C, more preferably from -120°C to 80°C.

[0101] Polyether polyols can be obtained in a known manner by alkoxylating suitable starter molecules under base catalysis or using double metal cyanide compounds (DMC compounds). Examples of suitable starter molecules for preparing polyether polyols are simple low molecular weight polyols, water, organic polyamines having at least two NH bonds, or any mixtures of such starter molecules.

[0102] Preferred starter molecules for preparing polyether polyols by alkoxylation, in particular by the DMC process, are in particular simple polyols, for example ethylene glycol, propane-1,3-diol and butane-1,4-diol, hexane-1,6-diol, neopentyl glycol, 2-ethylhexane-1,3-diol, glycerol, trimethylolpropane, pentaerythritol, and low molecular weight hydroxyl-containing esters of these polyols with dicarboxylic acids of the type mentioned below by way of example, or low molecular weight ethoxylation or propoxylation products of these simple polyols, or any mixtures of these modified or unmodified alcohols. Alkylene oxides suitable for alkoxylation are in particular ethylene oxide and / or propylene oxide, which can be used for the alkoxylation in any order or in the form of a mixture.

[0103] Suitable polyester polyols are described, for example, in EP-A-0994117 and EP-A-1273640. The polyester polyols can be prepared in a known manner from low molecular weight polycarboxylic acid derivatives, for example succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimerized fatty acids, trimerized fatty acids, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, citric acid or Trimellitic acid, prepared by polycondensation with low molecular weight polyols such as ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol, trimethylolpropane, 1,4-hydroxymethylcyclohexane, 2-methylpropane-1,3-diol, butane-1,2,4-triol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycol, or by ring-opening polymerization of cyclic carboxylic acid esters such as ε-caprolactone. In addition, hydroxycarboxylic acid derivatives such as lactic acid, cinnamic acid or ω-hydroxycaproic acid can also be polycondensed to form polyester polyols. However, polyester polyols of oleochemical origin can also be used. Such polyester polyols can be prepared, for example, by complete ring opening of epoxidized triglycerides of at least partially ethylenically unsaturated fatty acid-containing fat mixtures with one or more alcohols having 1 to 12 carbon atoms and by subsequent partial transesterification of the triglyceride derivatives into alkyl ester polyols having 1 to 12 carbon atoms in the alkyl group.

[0104] Polyurethane polyols are preferably prepared by reaction of polyester polyol prepolymers with suitable diisocyanates or polyisocyanates, as described, for example, in EP-A-1273640. Suitable polysiloxane polyols are described, for example, in WO-A-01 / 09260, wherein the polysiloxane polyols cited therein can preferably be used in combination with other polyhydroxy compounds, especially those having a higher glass transition temperature.

[0105] The polyacrylate polyols very particularly preferred according to the invention are generally copolymers and preferably have a mass average molecular weight Mw of 1000 to 20 000 daltons, in particular 1500 to 10 000 daltons, in each case measured by gel permeation chromatography (GPC) against polystyrene standards. The glass transition temperature of the copolymers is generally in the range of -100 to 100° C., in particular -50 to 80° C. (determined by DSC measurement in accordance with DIN EN ISO 11357-2).

[0106] The polyacrylate polyols preferably have an OH number of 60 to 250 mg KOH / g, in particular 70 to 200 KOH / g, and an acid number of 0 to 30 mg KOH / g. The acid number here indicates the mg of potassium hydroxide consumed to neutralize 1 g of the respective compound (DIN EN ISO 2114).

[0107] The preparation of suitable polyacrylate polyols is known per se to the person skilled in the art. They are obtainable by free-radical polymerization of ethylenically unsaturated monomers having hydroxyl groups or by free-radical copolymerization of ethylenically unsaturated monomers having hydroxyl groups with optional further ethylenically unsaturated monomers, such as ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, amyl acrylate, amyl methacrylate, hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, 3,3,5-trimethylhexyl acrylate, 3,3,5-trimethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate, lauryl acrylate or lauryl methacrylate, cycloalkyl acrylates and / or cycloalkyl methacrylates, such as cyclopentyl acrylate, cyclopentyl methacrylate, isobornyl acrylate, isobornyl methacrylate or in particular cyclohexyl acrylate and / or cyclohexyl methacrylate. Suitable ethylenically unsaturated monomers having hydroxyl groups are, in particular, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, in particular 4-hydroxybutyl acrylate and / or 4-hydroxybutyl methacrylate.

[0108] Further monomeric structural units for the polyacrylate polyols may be vinylaromatic hydrocarbons, for example vinyltoluene, α-methylstyrene or in particular styrene, amides or nitriles of acrylic or methacrylic acid, vinyl esters or vinyl ethers and also, in minor amounts, in particular acrylic acid and / or methacrylic acid.

[0109] Alternatively, it is preferred that the binder or component A) of the coating composition according to the invention contains a mixture of at least one polyacrylate polyol and up to 15% by weight, preferably 2 to 12% by weight, particularly preferably 5 to 10% by weight, based on the total amount of polyacrylate polyol, of at least one polyester polyol.

[0110] The coating composition according to the invention and also component A) and / or component B) of the two-component system according to the invention may also contain effective amounts of conventional auxiliaries and additives. The effective amount of solvents is preferably up to 150% by weight, particularly preferably up to 100% by weight, in particular up to 70% by weight, in each case based on the non-volatile components of the two-component system according to the invention or the coating composition according to the invention. The effective amount of further additives is preferably up to 25% by weight, particularly preferably up to 10% by weight, in particular up to 5% by weight, in each case again based on the non-volatile components.

[0111] Examples of suitable auxiliaries and additives are, in particular, light stabilizers, such as UV absorbers and sterically hindered amines (HALS), and also stabilizers, fillers and anti-settling agents, defoamers, anti-cratering agents and / or wetting agents, leveling agents, film-forming aids, reactive diluents, solvents, rheology control substances, slip additives and / or components which protect against contamination and / or improve the cleanability of the cured coating, and also matting agents.

[0112] The use of light stabilizers, especially UV absorbers such as substituted benzotriazoles, S-phenyltriazines or oxalanilides and sterically hindered amines, especially with a 2,2,6,6-tetramethylpiperidinyl structure, known as HALS, is described, for example, in A. Valet, Lichtschutzmittel für Lacke, Vincentz Verlag, Hannover, 1996.

[0113] Stabilizers, such as free radical scavengers and other polymerization inhibitors (eg hindered phenols) stabilize the coating components during storage and should prevent discoloration during curing. Acidic stabilizers (eg alkyl substituted partial phosphates) are also contemplated for component B).

[0114] The coating composition of the invention or the two-component system of the invention may also contain pigments, dyes and / or fillers. The pigments (including metal pigments or other effect pigments), dyes and / or fillers used are known to those skilled in the art.

[0115] Preferred fillers are those compounds which do not adversely affect the appearance of the coating. Examples are nanoparticles based on silica, alumina or zirconia; see also Lexikon "Lacke und Druckfarben" Georg Thieme Verlag, Stuttgart, 1998, pp. 250 to 252.

[0116] If fillers, matting agents or pigments are contained in the coating composition according to the invention or in the two-component system according to the invention, it may be advisable to add anti-settling agents in order to prevent separation of the components during storage.

[0117] Wetting agents and leveling agents improve the surface wettability and / or leveling of a coating. Examples include fluorosurfactants, silicone surfactants and certain polyacrylates. Rheology control additives are very important for controlling the properties of coating compositions or two-component systems during application and during the leveling phase on the substrate and are known, for example, from WO 94 / 22968, EP-A-0276501, EP-A-0249201 or WO 97 / 12945; crosslinked polymer microparticles, which are disclosed, for example, in EP-A-0008127; inorganic sheet silicates, for example aluminum magnesium silicates of the montmorillonite type, sodium magnesium and sodium magnesium fluorolithium sheet silicates; silicon dioxide, for example Or synthetic polymers with ionic and / or associative groups, for example polyvinyl alcohol, poly(meth)acrylamide, poly(meth)acrylic acid, polyvinylpyrrolidone, styrene-maleic anhydride or ethylene-maleic anhydride copolymers and derivatives thereof, or hydrophobically modified ethoxylated polyurethanes or polyacrylates.

[0118] The coating composition of the invention or the two-component system of the invention can be used solvent-free, but preferably comprises at least one solvent in component A) and / or component B).

[0119] Suitable solvents should be used in a manner known to those skilled in the art to match the coating composition used or the two-component system used and the application method. The solvents should dissolve the components used and promote their mixing, as well as avoid incompatibilities. In addition, during application and curing, they should match the coating to the ongoing crosslinking reaction so that a solvent-free coating with as good an appearance as possible and without defects such as cracks or pinholes is formed. Contemplated solvents include in particular the solvents used in two-component technology. Examples are ketones, such as acetone, methyl ethyl ketone or hexanone, esters, such as ethyl acetate, butyl acetate, methoxypropyl acetate, substituted glycols and other ethers, aromatic hydrocarbons, such as xylene or solvent naphtha (e.g. from Exxon-Chemie), and mixtures of the solvents described.

[0120] The coating composition according to the invention or the two-component system according to the invention can be used very well for coating substrates.

[0121] The present invention therefore further provides for the use of the polyisocyanate mixture according to the invention or of the coating composition according to the invention for producing a coating, preferably a repair coating, on a substrate, wherein the substrate is preferably an optionally pretreated vehicle body, in particular a vehicle body, or parts thereof.

[0122] In addition to such a use, another subject of the present invention is also a method for producing a coating, preferably a repair coating, on a substrate, comprising the following steps:

[0123] a) providing an optionally pretreated substrate;

[0124] b) applying at least one coating composition according to the invention;

[0125] c) Drying the coating composition at RT or by forced heating at a maximum of 60°C.

[0126] For use in step a) of the above-described method according to the invention, the substrate can be uncoated or coated. The coating can be, for example, the first coating of a vehicle, which is then used in the method according to the invention. Examples of primers, for example primers for automotive refinish coatings, include solvent-containing or water-based primers, primer surfacers or filler surfacers and basecoats familiar to the person skilled in the art, for example from A. Goldschmidt, H. Streitberger, "BASF Handbuch Lackiertechnik", Vincentz-Verlag, Hannover, D, 2002. Corresponding products are available, for example, from the company BASF Coatings GmbH, Münster, DE under the name "Glasurit" or from the company Axalta Coatings Systems Germany GmbH, Wuppertal, DE under the name "Spies Hecker Permasolid / Permahyd".

[0127] Suitable substrates are, for example, substrates comprising one or more materials, in particular so-called composite materials. According to the invention, substrates formed from at least two materials are referred to as composite materials. Suitable materials are preferably steel, aluminum or galvanized surfaces.

[0128] In the context of the present invention, the term plastics is also to be understood as meaning fiber-reinforced plastics, for example glass-fiber- or carbon-fiber-reinforced plastics, and plastic blends composed of at least two or more plastics.

[0129] Examples of suitable plastics according to the invention are ABS, AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, PA, PE, HDPE, LDPE, LLDPE, UHMWPE, PET, PMMA, PP, PS, SB, PUR, PVC, RF, SAN, PBT, PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM and UP (abbreviations according to DIN 7728 T1). These plastics can also be in the form of films or glass-fiber or carbon-fiber reinforced plastics.

[0130] In a preferred embodiment of the method according to the invention, the substrate has a surface which is made completely or partially of plastic and / or metal. Particularly preferably, the substrate consists at least partially of a composite material, in particular of a composite material comprising plastic and / or metal.

[0131] In another embodiment of the method according to the invention, the substrate comprises a metal; in particular, the substrate may consist of 80 wt.-%, 70 wt.-%, 60 wt.-%, 50 wt.-%, 25 wt.-%, 10 wt.-%, 5 wt.-%, 1 wt.-% metal.

[0132] In one embodiment of the present invention, the substrate provided in step a) is a vehicle body or a part thereof comprising one or more of the above materials. The vehicle body or a part thereof preferably comprises one or more materials selected from metal, plastic or a mixture thereof.

[0133] In step b) of the method of the invention, the application of the coating composition of the invention or the two-component system of the invention can be carried out by solution. Suitable application methods are, for example, printing, painting, rolling, casting, dipping, fluidized bed methods and / or spraying, for example compressed air spraying, airless spraying, high-speed rotation, electrostatic spraying (ESTA), optionally in combination with thermal spraying, for example hot gas thermal spraying. Particularly preferred here is application by spraying, for example compressed air spraying, airless spraying, high-speed rotation, electrostatic spraying (ESTA), optionally in combination with thermal spraying, for example hot gas thermal spraying.

[0134] The coating composition or two-component system applied in step b) can be applied after the components A) and B) have been mixed, or they can be mixed just before application. In the first case, the mixed two-component system has a limited shelf life, the so-called pot life, since the crosslinking reaction proceeds slowly after mixing. In the second case, the advantageous effect of the extended pot life is manifested, for example, in an improved coating appearance, since the coating composition or two-component system according to the invention can form a uniform film on the substrate.

[0135] It has been found to be particularly practical for the process according to the invention when the curing in step c) is carried out at a substrate temperature of from room temperature to at most 60° C.

[0136] The drying in step c) of the process according to the invention is carried out at 60° C. for less than 60 minutes, very particularly preferably for less than 30 minutes. Alternatively, drying at room temperature can be carried out for several hours.

[0137] Dry as used herein means that the coating system has reached a through-dry state (T1). The test is in accordance with DIN 53150:2002-09.

[0138] The process according to the invention thus enables the co-coating of pure metal substrates and thermoplastics or composite materials. A further advantage of the process according to the invention is that the selected polyisocyanates achieve a pot life of more than 30 minutes during the coating process, good gloss retention of more than 75 units of gloss 20° after the coating has dried, and simple manual mixing is possible by manual stirring with a stirring rod. Simple manual mixing (also referred to herein as good incorporation properties) is a further advantage of the polyisocyanate mixture according to the invention. This makes it particularly suitable for manual application areas, such as repair coating and wood coating.

[0139] The present invention also provides a coating produced or producible by the process according to the invention.

[0140] Another subject of the present invention is a coated substrate obtainable or produced by the process according to the invention, wherein the optionally pretreated substrate is preferably a vehicle body, in particular a vehicle body, or a part thereof, and / or preferably comprises one or more materials selected from metals, plastics or mixtures thereof. Due to the excellent properties of the polyisocyanate mixture according to the invention or the two-component system according to the invention, it is alternatively preferred that the optionally pretreated substrate is made of wood.

[0141] In a preferred embodiment of the present invention, the substrate coated with the coating composition of the present invention can be a vehicle body, in particular a vehicle body, or a part thereof, or furniture or other workpieces made of wood. The vehicle can be formed by one or more materials. Suitable materials are, for example, metal, plastic or a mixture thereof. The vehicle can be various vehicles known to those skilled in the art. For example, the vehicle can be a motor vehicle, a heavy goods vehicle, a motorcycle, a moped, a bicycle, etc. Preferably, the vehicle is a motor vehicle and / or a heavy goods vehicle, particularly preferably a motor vehicle.

[0142] In another preferred embodiment of the present invention, the substrate coated with the coating according to the invention is a vehicle body or a part thereof comprising one or more materials selected from metals, plastics or mixtures thereof.

[0143] The present invention will now be described in more detail using examples, but the present invention is not limited to these examples. Example:

[0144] Unless stated otherwise, all percentage data are based on weight.

[0145] The NCO content is determined by titration in accordance with DIN EN ISO 11909:2007-05.

[0146] The residual monomer content is measured by gas chromatography using an internal standard in accordance with DIN EN ISO 10283:2007-11.

[0147] All viscosity measurements were performed using a Physica MCR 51 rheometer from Anton Paar Germany GmbH (DE) according to DIN EN ISO 3219:1994-10 at a shear rate of 250 s -1 Next proceed.

[0148] The flow time is determined according to DIN EN ISO 2431:2012-03 using an ISO flow cup with a 4 mm nozzle.

[0149] The drying properties of the coating systems were determined according to DIN 53150:2002-09.

[0150] The gloss of the resulting coatings was measured by reflection at an angle of 20° in accordance with DIN EN ISO 2813:1999-06.

[0151] Determined on glass according to DIN EN ISO 1522:2007-04 Pendulum damping.

[0152] 13C-NMR spectra were recorded using a Bruker AVIIIHD 600NMR spectrometer equipped with a Z150361_001 (CP BBO 600SS3 BB-H&F-05ZE T) sample head. 512 scans were performed with a repetition time (D1) of 4 seconds and a measurement time (AQ) of 1.57 seconds.

[0153] The molecular weight is measured by gel permeation chromatography according to DIN EN ISO 13885-1:2021-11. Four columns are used (2x PSSSDV 50A, 5μ, 2x PSSSDV 100A, 5μ).

[0154] To test the solvent resistance of the coating, a small amount of the solvents xylene, 1-methoxy-2-propyl acetate, ethyl acetate and acetone were placed in a test tube, and a cotton pad was placed at the opening to form a solvent-saturated atmosphere in the test tube. The test tube was then placed on the surface of the coating applied to the glass through the cotton pad and left there for 1 or 5 minutes. After wiping off the solvent, the film was checked for damage / softening / loss of adhesion and rated (0 = no change, 5 = complete dissolution of the film). The ratings of the four solvents in each case are shown in the following order: xylene, 1-methoxy-2-propyl acetate, ethyl acetate and acetone, expressed in the form of four consecutive numbers. Gasoline resistance testing was similarly performed using E10 super gasoline.

[0155] Polyisocyanate 1 (Biuret polyisocyanate)

[0156] Biuret-containing HDI polyisocyanate was prepared according to EP-B 1158013 (Example 2b) by continuous reaction of 667 parts of HDI with 27 parts of hexamethylenediamine (HDA) at 280° C. in the presence of 1 part by weight of dibutyl phosphate as catalyst. After the reaction, unreacted HDI was removed by thin-film distillation at a temperature of 130° C. and a pressure of 0.1 mbar. The resulting polyisocyanate was diluted with butyl acetate to a polyisocyanate content of 75% by weight and had the following characteristic values.

[0157]

[0158] Polyisocyanate 2 (Polyisocyanurate-polyisocyanate)

[0159] HDI polyisocyanate containing isocyanurate groups, prepared by catalytic trimerization of HDI according to Example 11 of EP-A 330966, except that the catalyst solvent used was 2-ethylhexanol instead of 2-ethyl-1,3-hexanediol, and the reaction was stopped by adding dibutyl phosphate at an NCO content of 42.5% in the crude mixture. Subsequently, unreacted HDI was separated off by thin-film distillation at a temperature of 130° C. and a pressure of 0.2 mbar. The resulting polyisocyanurate-polyisocyanate had the following characteristic values.

[0160]

[0161] Polyisocyanate 3 (Polyisocyanurate-polyisocyanate)

[0162] HDI polyisocyanate containing isocyanurate groups, prepared by catalytic trimerization of HDI according to Example 11 of EP-A 330966, except that the reaction was stopped by adding dibutyl phosphate at an NCO content of 40% in the crude mixture. Subsequently, unreacted HDI was separated off by thin-film distillation at a temperature of 130° C. and a pressure of 0.2 mbar. The resulting polyisocyanate was diluted with butyl acetate to a polyisocyanate content of 90% by weight and had the following characteristic values.

[0163]

[0164] Polyisocyanate 4 (Polyisocyanurate / Allophanate Polyisocyanate)

[0165] 100 parts of hexamethylene diisocyanate (HDI) were pre-loaded and the temperature was adjusted to 105° C. At this temperature, 10 parts of trimethylolpropane were added under stirring. After the urethanization reaction was completed, the reaction temperature was reduced to 95° C. Then, the trimerization and allophanation reaction was started by adding a 0.5% solution of trimethylbenzylammonium hydroxide in 2-ethylhexanol. When an NCO value of 36% was reached, the reaction was terminated by adding an inhibitor solution (10% dibutyl phosphate in HDI), wherein the weight ratio of the inhibitor solution was 100 parts of catalyst solution to 3 parts of inhibitor solution. Stirring was continued at 95° C. for 30 minutes, and then the remaining monomeric HDI was separated off in a short-path evaporator at 140° C. and 0.1 mbar. The obtained polyisocyanate was diluted with butyl acetate to a polyisocyanate content of 80% by weight and had the following characteristic values.

[0166]

[0167] Polyisocyanate mixture 5 (The present invention)

[0168] 56 parts of polyisocyanate 2 were diluted with 24 parts of undiluted polyisocyanate 4 and 20 parts of butyl acetate. The resulting polyisocyanate mixture had the following characteristic values:

[0169]

[0170] Polyisocyanate mixture 6 (The present invention)

[0171] 32 parts of polyisocyanate 2 were diluted with 48 parts of undiluted polyisocyanate 4 and 20 parts of butyl acetate. The resulting polyisocyanate mixture had the following characteristic values:

[0172]

[0173] Examples 1, 2, 3, 4 and 5 (Coating composition and coating technology testing; Invention and Comparative Examples)

[0174] To different weight portions of commercially available polyester polyols ( 0.80 parts by weight of a 50% solution of a commercially available free radical scavenger (Tinuvin 292, BASF SE) in butyl acetate, 1.20 parts by weight of a 50% solution of a commercially available UV absorber (Tinuvin 384-2, BASF SE) in butyl acetate, 1.20 parts by weight of a 10% solution of a commercially available leveling agent (Byk331, Byk-Chemie GmbH), and 2.50 parts by weight of a 1% solution of dibutyltin dilaurate (DBTL) in butyl acetate were added to XP 775; Covestro AG, Leverkusen, DE) (solids content 75% and OH content (based on the delivery form) 9.5%, corresponding to an equivalent weight of 180 g / equivalent OH) and mixed uniformly by vigorous stirring.

[0175] Then, different weight portions of a solvent mixture consisting of equal weight portions of butyl acetate, MPA and xylene were uniformly incorporated at room temperature by vigorous stirring in order to obtain a nonvolatile proportion of 56 weight % in the coating to be processed.

[0176] Different weight portions of polyisocyanates 1, 3, 4 and polyisocyanate mixtures 5 and 6 (also in butyl acetate, corresponding to an equivalent ratio of isocyanate groups to hydroxyl groups of 1:1) were then mixed in manually using a stirring rod as crosslinker component.

[0177] Coating compositions 1 to 5 were applied to glass plates in each case with a wet film thickness of about 150 μm by means of a thin-film coating frame and cured at 60° C. for 30 minutes and aged at 60° C. for 16 hours.

[0178] Table 1 below shows the compositions (in parts by weight) of coating compositions 1 to 5, and Table 2 shows a comparison of the application technology test results of the resulting coatings.

[0179] Table 1: Comparative Examples 1, 2 and 3 and Inventive Examples 4 and 5 - Composition of the Coating Compositions

[0180]

[0181]

[0182] Table 2 : Comparative Examples 1, 2 and 3 and Examples 4 and 5 of the present invention - coating technical performance

[0183]

[0184] As can be seen from Table 2, the biuret-based and allophanate-based isocyanate systems (Comparative Examples 1 and 3) achieve high gloss and good solvent resistance, but unsatisfactory processing times due to a significant increase in viscosity after 30 minutes. In contrast, the isocyanurate-based system (Comparative Example 2) achieves good processing times, but only an inadequate gloss.

[0185] The chemical resistance also does not quite reach the high level of the comparative system, especially with respect to acetone as test substance.

[0186] Only the polyisocyanate mixtures according to the invention form high-solids coating systems (non-volatile fraction (nfA) during processing>56% by weight) which exhibit high chemical resistance as well as long processing times and good appearance.

Claims

1. A polyisocyanate mixture comprising at least one polyisocyanurate-polyisocyanate and at least one polyalophanate-polyisocyanate, wherein the polyisocyanate mixture The monomeric diisocyanate content, determined by gas chromatography using an internal standard according to DIN EN ISO 10283:2007-11, is <0.10% by weight. an isocyanurate group content of ≥40 mol % to ≤85 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, determined by NMR spectroscopy, and The allophanate group content determined by NMR spectroscopy is ≧15 mol % to ≦60 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture.

2. The polyisocyanate mixture according to claim 1, characterized in that The isocyanurate group content determined by NMR spectroscopy is ≥45 mol % to ≤80 mol %, preferably ≥50 mol % to ≤75 mol %, particularly preferably ≥53 mol % to ≤72 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture, and / or The allophanate group content determined by NMR spectroscopy is ≥20 mol % to ≤55 mol %, preferably ≥25 mol % to ≤50 mol %, particularly preferably ≥28 mol % to ≤47 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture.

3. The polyisocyanate mixture according to claim 1 or 2, characterized in that: The weight-average molecular weight determined according to DIN EN ISO 13885-1:2021-11 is ≥1000 g / mol to ≤3000 g / mol, preferably ≥1300 g / mol to ≤2700 g / mol, particularly preferably ≥1500 g / mol to ≤2500 g / mol.

4. The polyisocyanate mixture according to any one of claims 1 to 3, characterized in that The polydispersity determined in accordance with DIN 55672-1:2016-03 is ≥1.5 to ≤2.5, preferably ≥1.7 to ≤2.

2.

5. The polyisocyanate mixture according to any one of claims 1 to 4, characterized in that The at least one polyalophanate-polyisocyanate is obtained by oligomerization of at least one aliphatic, cycloaliphatic or araliphatic monomeric diisocyanate having a molecular weight of ≧140 to ≦400 g / mol and at least one hydroxy-functional compound having an OH functionality of ≧3 and ≦6.

6. The polyisocyanate mixture according to any one of claims 1 to 5, characterized in that The at least one polyisocyanurate-polyisocyanate contains one or more isocyanurate groups which are each chemically bonded together via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of ≥56 to ≤316 g / mol, preferably each via a 1,4-butyl or 1,6-hexyl group, particularly preferably each via a 1,6-hexyl group.

7. The polyisocyanate mixture according to any one of claims 1 to 6, characterized in that The at least one polyalophanate-polyisocyanate comprises one or more allophanate groups which are each chemically bonded together via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of ≥56 to ≤316 g / mol, preferably each via a 1,4-butyl or 1,6-hexyl group, particularly preferably each via a 1,6-hexyl group.

8. A method for preparing a polyisocyanate mixture according to any one of claims 1 to 7, characterized in that At least one polyisocyanurate-polyisocyanate and at least one polyalophanate-polyisocyanate are mixed, wherein preferably, the at least one polyisocyanurate-polyisocyanate has a weight-average molecular weight of ≤1000 g / mol determined according to DIN EN ISO 13885-1:2021-11 and / or the at least one polyalophanate-polyisocyanate has a weight-average molecular weight of ≥3000 g / mol determined according to DIN EN ISO 13885-1:2021-11.

9. The method according to claim 8, characterized in that 30-70 parts by weight of the at least one polyisocyanurate-polyisocyanate and 70-30 parts by weight of the at least one polyalophanate-polyisocyanate are mixed.

10. A coating composition comprising at least one polyisocyanate mixture according to any one of claims 1 to 7 and at least one binder reactive toward isocyanate groups, or at least one polyisocyanate mixture obtainable or produced by a process according to claim 8 or 9 and at least one binder reactive toward isocyanate groups.

11. The coating composition according to claim 10, characterized in that It comprises the at least one binder reactive toward isocyanate groups in component A) and the at least one polyisocyanate mixture in component B) according to any one of claims 1 to 7 or the at least one polyisocyanate mixture in component B) obtainable or prepared by the method according to claim 8 or 9, and / or the at least one binder reactive toward isocyanate groups is a polyhydroxy compound, preferably polyether polyols, polyester polyols, polyurethane polyols, polysiloxane polyols, polycarbonate polyols, polyether polyamines, polybutadiene polyols, polyacrylate polyols and / or polymethacrylate polyols and copolymers thereof, particularly preferably polyester polyols, polyacrylate polyols or any mixtures thereof.

12. The coating composition according to any one of claims 10 to 11, characterized in that The at least one isocyanate-reactive binder comprises at least one hydroxy-functional compound having a hydroxyl group content of ≥2.0% by weight, preferably ≥3.0% by weight, particularly preferably ≥3.5% by weight, based on the solids content of the isocyanate-reactive binder.

13. Use of a polyisocyanate mixture according to any one of claims 1 to 7 or a coating composition according to any one of claims 10 to 12 for producing a coating on a substrate, wherein the substrate is preferably an optionally pretreated body, in particular a body of a vehicle, or parts thereof.

14. A method for preparing a coating on a substrate, comprising the steps of: a) providing an optionally pretreated substrate; b) applying at least one coating composition according to any one of claims 10 to 12; c) curing the coating composition by applying heat.

15. A coated substrate obtainable or produced by the process according to claim 14, wherein the optionally pretreated substrate is preferably a vehicle body, in particular a vehicle body, or a part thereof, and / or preferably comprises one or more materials selected from metals, plastics or mixtures thereof.

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