Polyisocyanate mixture

Abstract

The present invention relates to a polyisocyanate mixture containing at least one polyisocyanurate polyisocyanate and at least one polyallophanate polyisocyanate, wherein the polyisocyanate mixture has an amount of monomer diisocyanate of < 0.10 wt.%, determined in accordance with DIN EN ISO 10283:2007-11 by gas chromatography using an internal standard, a isocyanurate group portion of ≥ 40 mol% to ≤ 85 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture, and an allophanate group portion of ≥ 15 mol% to ≤ 60 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture.

Description

[0001] Polyisocyanate mixture

[0002] The invention relates to a polyisocyanate mixture and its use. Further subjects of the invention are a coating composition containing the polyisocyanate mixture, a process for producing a coating on a substrate, the coating obtainable by this process, and the coated substrate.

[0003] For high-quality, lightfast coatings, coatings made from aliphatic polyisocyanates and polyols, such as polyacrylate polyols, polyester polyols, or polycarbonate polyols, are particularly popular. Derivatives of 1,6-hexamethylene diisocyanate (HDI) are particularly used as polyisocyanates for these high-quality coatings.

[0004] Particularly with increasing demands on the durability of a coating system, e.g., in terms of weather and chemical resistance, coupled with high abrasion resistance, gloss retention, and lightfastness, systems with high OH group content are becoming increasingly necessary on the binder side. Due to their chemical composition, such systems have a higher polarity than standard binders.

[0005] EP 0 277 353 A1 describes polyisocyanates with a biuret structure, which are said to be highly compatible. However, monomer stability can be reduced in biuret-containing polyisocyanates.

[0006] Polyisocyanurates are also preferred as crosslinking agents in these applications, as their lower viscosity enables the formulation of high-solids, VOC-compliant (“volatile organic compounds”) coating systems. Such polyisocyanurates are described in DE-A2 839 133. However, they often exhibit lower compatibility in coating systems compared to biuret-containing polyisocyanates.

[0007] As an alternative to pure polyisocyanurates, WO 2019 / 061019 A1 describes polyisocyanate crosslinkers with high allophanate group content, which are produced by the presence of alcohols during catalytic trimerization. However, these have the disadvantage of high viscosity.

[0008] There was therefore still a need to provide a polyisocyanate mixture that, while offering high chemical resistance, has a long processing time and good incorporation properties, as well as good appearance of the resulting coatings.

[0009] Therefore, the object of the present invention was to provide a polyisocyanate mixture that, while offering high chemical resistance, has a long processing time and good incorporation properties, as well as good appearance of the resulting coatings. This object is achieved according to the invention by a polyisocyanate mixture containing at least one polyisocyanurate polyisocyanate and at least one polyallophanate polyisocyanate, wherein the polyisocyanate mixture has a monomeric diisocyanate content of <0.10 wt.-%, determined according to DIN EN ISO 10283:2007-11 by gas chromatography with an internal standard, an isocyanurate group content of > 40 mol-% to < 85 mol-%, determined by NMR spectroscopic analysis and 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 spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate mixture.

[0010] According to the invention, the terms "comprising" or "containing" preferably mean "consisting essentially of," and particularly preferably "consisting of." The further embodiments mentioned in the claims and in the description can be combined in any desired way, unless the context clearly indicates otherwise.

[0011] The polyisocyanate mixture according to the invention represents a physical mixture and thus differs from a purely chemically produced polyisocyanate, for example, with regard to the oligomer distribution, since in the polyisocyanate mixture according to the invention there is no statistical distribution of the allophanate and isocyanurate groups over the entirety of polyisocyanate oligomers.

[0012] The at least one polyisocyanurate polyisocyanate may contain other structural units, such as uretdione structures but also allophanate structures, if at all only in minor amounts, with isocyanurate structures in any case making up the main proportion, preferably more than 80 mol% and particularly preferably more than 90 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups, allophanate groups and optionally further oligomerization structures of the polyisocyanurate polyisocyanate.According to the invention, isocyanurate-iminooxadiazinedione polyisocyanates can also be used as polyisocyanurate polyisocyanates, which have a proportion of 5 to 20 mol% of iminooxadiazinedione structures (also referred to as asymmetric trimers) and an isocyanurate content of at least 50 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups, iminooxadiazinedione groups, allophanate groups, and optionally other oligomerization structures of the polyisocyanurate polyisocyanate. Such isocyanurate-iminooxadiazinedione polyisocyanates are also referred to herein as polyisocyanurate polyisocyanates.

[0013] The at least one polyallophanate polyisocyanate may contain other structural units, such as uretdione structures, iminoxadiazinedione structures (so-called asymmetric trimers), but also isocyanurate structures—if at all, only in minor amounts, with the allophanate structures always constituting the majority. However, according to the invention, allophanate-isocyanurate mixed products can also be used that contain an allophanate content of at least 50 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups, iminooxadiazinedione groups, allophanate groups, and optionally further oligomerization structures of the polyallophanate polyisocyanate. Such allophanate-isocyanurate mixed products are also referred to herein as polyallophanate polyisocyanates.

[0014] The contents (mol-%) of the isocyanurate and allophanate structures present in the polyisocyanate mixture according to the invention or in the individual polyisocyanates used for the mixture are preferably determined from the integrals of proton-decoupled 13C-NMR spectra were calculated and refer to the sum of the isocyanurate and allophanate structures present. A Bruker AV III HD 600 NMR spectrometer with probe head Z150361 001 (CP BBO 600SS3 BB-H&F-05 ZE T) was used for 512 scans. With a repetition time (Dl) of 4 s and a measurement time (AQ) of 1.57 s, experience shows that very similar carbonyl carbon atoms are comparable via integration. In the case of hexamethylene diisocyanate-based polyisocyanates dissolved in CDCl3, the individual structural elements exhibit the following chemical shifts (in ppm): isocyanurate: 148.4; iminooxadiazinedione: 147.8, 144.3, and 135.3; Allophanate: 155.7 and 153.8. Chemical shifts (in ppm) of any structural elements present for polyisocyanates based on hexamethylene diisocyanate dissolved in CDCl3 are as follows: Uretdione: 157.1; biuret: 155.5; urethane: 156.3; oxadiazinetrione: 147.8 and 143.9; uretonimine: 158.7 and 144.6.

[0015] The weight-average molecular weight of both the polyisocyanate mixture and the individual polyisocyanates used for the mixture is determined in the present invention by gel permeation chromatography according to DIN EN ISO 13885-1:2021-1 using polystyrene as standard.

[0016] The content of monomeric diisocyanates is determined according to DIN EN ISO 10283:2007-11 using gas chromatography with an internal standard.

[0017] In the context of the invention, the pot life (hereinafter also referred to as “potlife”) is defined as the time in which the coating composition has doubled its viscosity (indirectly determined by doubling the flow time in the DIN cup, 4 mm).

[0018] An “organic compound” or “organic residue” contains at least one unit comprising a covalent carbon-hydrogen bond.

[0019] For the purposes of this document, the term "aliphatic" is defined as non-aromatic hydrocarbon groups that are saturated or unsaturated. For the purposes of this document, the term "araliphatic" is defined as hydrocarbon radicals that consist of both an aromatic and a saturated or unsaturated hydrocarbon group directly bonded to the aromatic radical.

[0020] As used herein, the term "alicyclic" or "cycloaliphatic" is defined as optionally substituted, carbocyclic or heterocyclic compounds or moieties that are not aromatic.

[0021] "At least one," as used herein, refers to 1 or more, for example, 2, 3, 4, 5, 6, 7, 8, 9, or more. In the context of components of the compounds described herein, this statement does not refer to the absolute amount of molecules, but rather to the type of component. "At least one polyallophanate polyisocyanate," therefore, means, for example, that only one type of compound or several different types of compounds of this type may be present, without specifying the amount of the individual compounds.

[0022] Numerical ranges specified in the format "in / from x to y" include the specified values. If multiple preferred numerical ranges are specified in this format, it is understood that all ranges resulting from the combination of the different endpoints are also included.

[0023] 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% and particularly preferably > 53 mol% to < 72 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture, and / or an allophanate group content of > 20 mol% to < 55 mol%, preferably > 25 mol% to < 50 mol% and particularly preferably > 28 mol% to < 47 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture. This results in the advantage that a further extended pot life is achieved with at least consistently good compatibility in the paint system.

[0024] In a further preferred embodiment, the polyisocyanate mixture according to the invention has a weight-average molecular weight of > 1000 g / mol to < 3000, preferably > 1300 g / mol to < 2700 g / mol, and particularly preferably > 1500 g / mol to < 2500 g / mol, determined according to EN ISO 13885-1:2021-11. This results in the further advantage of achieving a further improved pot life with good chemical resistance.

[0025] In a further preferred embodiment, the polyisocyanate mixture according to the invention has a polydispersity of > 1.5 to < 2.5, preferably > 1.7 to < 2.2, determined according to DIN 55672-1:2016-03. This also results in the further advantage that a further improved potlife is achieved with good chemical resistance, and can be increased even further in combination with the two aforementioned preferred embodiments. Suitable starting compounds for the preparation of polyisocyanurate polyisocyanates and polyallophanate polyisocyanates suitable for preparing the polyisocyanate mixture according to the invention are any monomeric diisocyanates with aliphatically, cycloaliphatically, araliphatically and / or aromatically bound isocyanate groups, which can be prepared by any process, e.g. by phosgenation or by a phosgene-free route, for example by urethane cleavage.

[0026] Suitable monomeric diisocyanates, hereinafter also referred to as starting diisocyanates, are, for example, those in the molecular weight range 168 to 400 g / mol, such as 1,6-diisocyanatohexane (HDI), l,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-l,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,9-diisocyanatononane, 1,10-diisocyanatodecane, 1,3- and

[0027] 1,4-Diisocyanatocyclohexane, l,4-Diisocyanato-3,3,5-trimethylcyclohexane, l,3-Diisocyanato-2-methylcyclohexane, 1,3-Diisocyanato-4-methylcyclohexane, 1-Isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (Isophorone diisocyanate; IPDI), 1-Isocyanato-l-methyl-4(3)-isocyanatomethylcyclohexane, 2,4'- and 4,4'-Diisocyanatodicyclohexylmethane (Hn-MDI), 1,3- and

[0028] 1,4-Bis(isocyanatomethyl)cyclohexane, 4,4'-Diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-Diisocyanato-3,3',5,5'-tetramethyldicyclohexylmethane, 4,4'-Diisocyanato-l,l'-bi(cyclohexyl), 4,4'-Diisocyanato-3 ,3'-dimethyl-1,1'-bi(cyclohexyl), 4,4'-diisocyanato-2,2',5,5'-tetra-methyl-1,1'-bi(cyclohexyl), 1,8-diisocyanato-p-menthane, 1,3-diisocyanatoadamantane, l,3-dimethyl-5,7-diisocyanatoadamantane, 1,3- and l,4-bis-(isocyanatomethyl)benzene (XDI), 1,3- and 1,4-Bis(l-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-tolylene diisocyanate, and any mixtures of these isomers, diphenylmethane 2,4'- and / or 4,4'-diisocyanate, and naphthylene 1,5-diisocyanate, as well as any mixtures of such diisocyanates. Other suitable diisocyanates can also be found, for example, in Justus Liebig's Annalen der Chemie, 562, 1949, 75-136.

[0029] Particularly preferred starting diisocyanates are linear or branched, aliphatic or cycloaliphatic diisocyanates of the type mentioned. Very particularly preferred starting diisocyanates are 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 desired mixtures of these diisocyanates. 1,6-diisocyanatohexane (HDI) is particularly suitable.

[0030] The starting diisocyanates can be converted to polyisocyanurate polyisocyanates and / or polyallophanate polyisocyanates using various known modification processes. These polyisocyanurate polyisocyanates and polyallophanate polyisocyanates are blended to obtain the polyisocyanate mixture according to the invention. Any desired mixing ratios can be used, which the skilled person can select without great effort based on the individual polyisocyanate characteristics, such as the molar content of isocyanurate or allophanate groups by NMR spectroscopic analysis or, if preferred, determination of the weight-average molecular weight according to the aforementioned DIN EN ISO 13885-1:2021-11 using polystyrene as the standard.

[0031] In a further preferred embodiment, the at least one polyisocyanurate polyisocyanate comprises one or more isocyanurate groups which are each chemically bonded to one another via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of > 56 to < 316 g / mol, preferably in each case via a 1,4-butyl or 1,6-hexyl group and particularly preferably in each case via a 1,6-hexyl group.

[0032] In this context, a 1,4-butyl or 1,6-hexyl group is understood to mean that a hydrogen atom is missing at positions 1 and 4, or 1 and 6, respectively, and the group is chemically bonded via these atoms. The "1,4-butyl or 1,6-hexyl group" can also be referred to as a "1,4-butanediyl" or "1,6-hexanediyl group" in this context.

[0033] A preferred modification reaction for the preparation of polyisocyanurate polyisocyanates for the polyisocyanate mixture according to the invention is, for example, the catalytic trimerization of starting diisocyanates. In principle, any compounds that accelerate the trimerization of isocyanate groups to isocyanurate structures can be used as catalysts.

[0034] Suitable catalysts for the production of polyisocyanurate polyisocyanates include, 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. Other suitable catalysts are the tertiary hydroxyalkylamines described in GB 2 221 465, such as triethanolamine, N-methyldiethanolamine, dimethylethanolamine, N-isopropyldiethanolamine, and l-(2-hydroxyethyl)pyrrolidine, or the catalyst systems known from GB 2 222 161, consisting of mixtures of tertiary bicyclic amines, such as DBU, with simple low-molecular-weight aliphatic alcohols.

[0035] A variety of different metal compounds are also suitable as trimerization catalysts. Suitable catalysts include, for example, the octoates and naphthenates of manganese, iron, cobalt, nickel, copper, zinc, zirconium, cerium or lead or mixtures thereof with acetates of lithium, sodium, potassium, calcium or barium, described as catalysts in DE-A 3 240 613, the sodium and potassium salts of linear or branched alkanecarboxylic acids with up to 10 C atoms, such as propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid and undecylic acid, known from DE-A 3 219 608, the alkali or alkaline earth metal salts of aliphatic, cycloaliphatic or aromatic mono- and polycarboxylic acids with 2 to 20 C atoms, such as sodium or potassium benzoate, known from GB 1 391 066 A and GB 1 386 399 A known alkali phenolates, such asSodium or potassium phenolate, the alkali and alkaline earth oxides, hydroxides, carbonates, alcoholates and phenolates known from GB 809 809, alkali metal salts of enolizable compounds and metal salts of weak aliphatic or cycloaliphatic carboxylic acids, such as sodium methoxide, sodium acetate, potassium acetate, sodium acetoacetic ester, lead 2-ethylhexanoate and lead naphthenate, the basic alkali metal compounds complexed with crown ethers or polyether alcohols known from EP-A 0 056 158 and EP-A 0 056 159, such as complexed sodium or potassium carboxylates, the pyrrolidinone potassium salt known from EP-A 0 033 581, the mono- or polynuclear complex compounds of titanium, zirconium and / or hafnium known from EP-A 2 883 895, such as Zirconium tetra-n-butylate, zirconium tetra-2-ethylhexanoate and zirconium tetra-2-ethylhexylate, as well as tin compounds of the type described in European Polymer Journal, 16, 1979, 147-148, such asDibutylzinndichlorid, Diphenylzinndichlorid, Triphenylstannanol, Tributylzinnacetat, Tributylzinnoxid, Zinnoctoat, Dibutyl(dimethoxy)stannan und Tributylzinnimidazolat.

[0036] Further trimerization catalysts suitable for the preparation of polyisocyanurate polyisocyanates are, for example, the quaternary ammonium hydroxides known from DE-A 1 667 309, EP-A 0 013 880 and EP-A 0 047 452, such as tetraethylammonium hydroxide, trimethylbenzylammonium hydroxide, N,N-dimethyl-N-dodecyl-N-(2-hydroxyethyl)ammonium hydroxide, N-(2-hydroxyethyl)-N,N-dimethylN-(2,2'-dihydroxymethylbutyl)ammonium hydroxide and l-(2-hydroxyethyl)-l,4-diazabicyclo-[2.2.2]octane hydroxide (monoadduct of ethylene oxide and water with l,4-diazabicyclo-[2.2.2]octane), the quaternary ammonium hydroxides known from EP-A 37 65 or EP-A 10 589 Hydroxyalkylammonium hydroxides, such as N,N,N-trimethyl-N-(2-hydroxyethyl)-ammonium hydroxide, the trialkylhydroxylalkylammonium carboxylates known from DE-A 2631733, EP-A 0 671 426, EP-A 1 599 526 and US 4,789,705, such as N,N,N-trimethyl-N-2-hydroxypropylammonium-p-tert.-butylbenzoate and N,N,N-trimethyl-N-2-hydroxypropylammonium 2-ethylhexanoate, the quaternary benzylammonium carboxylates known from EP-A 1 229 016, such as 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-tributyl-N-(4-methoxybenzyl)ammonium pivalate, the tetrasubstituted ammonium a-hydroxycarboxylates known from WO 2005 / 087828, such as tetramethylammonium lactate, those known from EP-A 0 339 396, EP-A 0 379 914 and EP-A 0 443 167 known quaternary ammonium or phosphonium fluorides, such asN-methyl-N,N,N-trialkylammonium fluorides with Cs-Cio-alkyl radicals, N,N,N,N-tetra-n-butylammonium fluoride, N,N,N-trimethyl-N-benzylammonium fluoride, tetramethylphosphonium fluoride, tetraethylphosphonium fluoride or tetra-n-butylphosphonium fluoride, the quaternary ammonium and phosphonium polyfluorides known from EP-A 0 798 299, EP-A 0 896 009 and EP-A 0 962 455, such as benzyltrimethylammonium hydrogen polyfluoride, the tetraalkylammonium alkyl carbonates known from EP-A 0 668 271, which are obtainable by reacting tertiary amines with dialkyl carbonates, or betaine-structured quaternary ammonioalkyl carbonates, the quaternary Ammonium hydrogen carbonates, such as choline bicarbonate, the quaternary ammonium salts known from EP 0 102 482, obtainable from tertiary amines and alkylating esters of phosphorus acids, such asReaction products of triethylamine, DABCO or N-methylmorpholine with methanephosphonic acid dimethyl ester, or the tetrasubstituted ammonium salts of lactams known from WO 2013 / 167404, such as trioctylammonium caprolactamate or dodecyltrimethylammonium caprolactamate.

[0037] These catalysts can be used individually or in the form of any desired mixtures. Preferred catalysts are ammonium and phosphohonium salts of the type mentioned above, in particular trialkylhydroxyalkylammonium carboxylates, benzylammonium carboxylates, quaternary ammonium hydroxides,

[0038] Hydroxyalkylammonium hydroxides, ammonium or phosphonium fluorides, and ammonium and phosphonium polyfluorides of the type mentioned. Particularly preferred trimerization catalysts are the quaternary ammonium hydroxides and ammonium and phosphonium polyfluorides of the type mentioned.

[0039] In the preparation of polyisocyanurate polyisocyanates for the polyisocyanate mixture according to the invention, the trimerization catalyst is generally used in a concentration of 0.0005 to 5.0 wt. %, preferably 0.0010 to 2.0 wt. %, and particularly preferably 0.0015 to 1.0 wt. %, based on the amount of starting diisocyanates used.

[0040] The trimerization catalysts are preferably added to the starting diisocyanates in bulk. However, if necessary, the trimerization catalysts mentioned can also be used dissolved in a suitable organic solvent to improve their compatibility. The degree of dilution of the catalyst solutions can be freely selected within a very wide range. Such catalyst solutions are typically catalytically effective at a concentration of 0.01 wt.% or higher.

[0041] Suitable catalyst solvents are, for example, solvents inert towards 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-methoxypropyl-2-acetate, 3-methoxy-n-butyl acetate, propylene glycol diacetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, lactones such as ß-propiolactone, γ-butyrolactone, s-caprolactone and s-methylcaprolactone, but also solvents such as N-methylpyrrolidone and N-methylcaprolactam, 1,2-propylene carbonate, methylene chloride, Dimethyl sulfoxide, triethyl phosphate or any mixtures of such solvents.

[0042] If catalyst solvents are used in the production of suitable polyisocyanurate polyisocyanates, catalyst solvents that carry isocyanate-reactive groups and can be incorporated into the polyisocyanurate polyisocyanate are preferred. Examples of such solvents are mono- or polyhydric simple alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, the isomeric butanediols, 2-ethyl-1,3-hexanediol, or glycerol. Ether alcohols, such as l-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 higher molecular weight polyethylene glycols, polypropylene glycols, mixed

[0043] Polyethylene / polypropylene glycols and their monoalkyl ethers; ester alcohols such as ethylene glycol monoacetate, propylene glycol monolaurate, glycerol mono- and diacetate, glycerol monobutyrate or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate; unsaturated alcohols such as allyl alcohol, 1,1-dimethylallyl alcohol or olein alcohol; araliphatic alcohols such as benzyl alcohol; N-monosubstituted amides such as N-methylformamide, N-methylacetamide, cyanoacetamide or 2-pyrrolidinone or any mixtures of such solvents. In the case of optional use of such catalyst solvents carrying groups reactive towards isocyanates, any allophanate groups formed thereby are counted towards the molar proportion of allophanate groups according to the invention and towards the total amount of isocyanurate and allophanate groups in the polyisocyanate mixture according to the invention.

[0044] According to the invention, isocyanurate-iminooxadiazinedione polyisocyanates containing an isocyanurate content of at least 50 mol% can also be used as polyisocyanurate polyisocyanates; these are also referred to herein as polyisocyanurate polyisocyanates within the scope of the invention. Such iminooxadiazinedione groups (also called asymmetric trimers) can be prepared by processes described, for example, in EP-A 0 798 299, EP-A 0 962 454, WO2015 / 124504, or WO 2017 / 029266.

[0045] The preparation of polyisocyanurate polyisocyanates for the polyisocyanate mixture according to the invention is carried out by processes known per se, as described, for example, in the publications mentioned above in the list of suitable trimerization catalysts.

[0046] As a rule, the starting diisocyanates are admixed with a suitable trimerization catalyst in the above-mentioned amount at a temperature between 0 and 150°C, preferably 20 to 130°C, particularly preferably 40 to 120°C, optionally under an inert gas such as nitrogen, and optionally in the presence of solvents, for example those listed above as possible catalyst solvents inert toward isocyanate groups, whereupon the trimerization reaction begins with the formation of isocyanurate structures. As with all preparation processes for polyisocyanates for use according to the invention, the course of the reaction can be monitored, for example, by titrimetric determination of the NCO content according to DIN EN ISO 11909:2007-05.

[0047] Once the desired degree of oligomerization is reached, the trimerization reaction is terminated. The "degree of oligomerization" is defined as the percentage of the isocyanate groups originally present in the reaction mixture that are consumed during the production process, preferentially forming isocyanurate structures. Depending on the type of starting diisocyanate or mixture of starting diisocyanates used, the minimum desired degree of oligomerization can vary.

[0048] The reaction can be terminated at the desired degree of oligomerization, for example, by cooling the reaction mixture to room temperature. However, the reaction is preferably terminated by adding a catalyst poison and, if appropriate, by briefly heating the reaction mixture, for example, to a temperature above 80°C.

[0049] Suitable catalyst poisons are, for example, inorganic acids such as hydrochloric acid, phosphorous acid or phosphoric acid, acid chlorides such as acetyl chloride, benzoyl chloride or isophthaloyl dichloride, sulfonic acids and sulfonic acid esters such as methanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, dodecylbenzenesulfonic acid, p-toluenesulfonic acid methyl ester and ethyl ester, mono- and dialkyl phosphates such as monotridecyl phosphate, dibutyl phosphate and dioctyl phosphate but also silylated acids such as methanesulfonic acid trimethylsilyl ester, trifluoromethanesulfonic acid trimethylsilyl ester,

[0050] Phosphoric acid tris-(trimethylsilyl ester) and phosphoric acid diethyl ester trimethylsilyl ester.

[0051] The amount of catalyst poison required to terminate the reaction depends on the amount of trimerization catalyst used; generally, an equivalent amount of catalyst poison is used, based on the amount of catalyst initially used. However, if possible catalyst losses during the reaction are taken into account, 20 to 80 equivalent percent of catalyst poison, based on the amount of catalyst originally used, may be sufficient to terminate the reaction.

[0052] The catalyst poisons mentioned can be used either as such or dissolved in a suitable solvent. Suitable solvents include those already described above as possible catalyst solvents, or mixtures thereof. The degree of dilution can be freely selected within a very wide range; for example, solutions with a concentration of 1 wt.% or higher are suitable.

[0053] In addition to the solvents mentioned, the above-mentioned starting diisocyanates can also serve as solvents for the catalyst poisons, provided they are sufficiently inert toward isocyanate groups so that storage-stable solutions can be prepared. After the reaction has ended, the reaction mixture is preferably freed from volatile constituents (such as excess starting diisocyanates and any solvents used) by thin-film distillation in a vacuum, for example at a pressure of less than 1.0 mbar, preferably less than 0.5 mbar, particularly preferably less than 0.2 mbar, under the mildest possible conditions, for example at a temperature of 100 to 200°C, preferably 120 to 180°C.

[0054] It is also possible to separate the above-mentioned volatile components from the polyisocyanate by extraction with suitable solvents that are inert towards isocyanate groups, for example aliphatic or cycloaliphatic hydrocarbons such as pentane, hexane, heptane, cyclopentane or cyclohexane.

[0055] The residual content of monomeric diisocyanate after distillation or extraction is preferably <0.50 wt.%, particularly preferably <0.3 wt.%, and particularly preferably <0.10 wt.%. The proportion of monomeric diisocyanate in the at least one polyisocyanurate polyisocyanate may be greater than 0.10 wt.%, as long as it is less than 0.10 wt.% in the polyisocyanate mixture according to the invention.

[0056] In addition to the at least one polyisocyanurate polyisocyanate, the polyisocyanate mixture according to the invention also contains at least one polyallophanate polyisocyanate, which is obtained, for example, by reacting the above-mentioned starting diisocyanates with hydroxy-functional compounds.

[0057] In a further preferred embodiment, the at least one polyallophanate polyisocyanate comprises one or more allophanate groups which are each chemically bonded to one another via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of > 56 to < 316 g / mol, preferably in each case via a 1,4-butyl or 1,6-hexyl group and particularly preferably in each case via a 1,6-hexyl group.

[0058] In this context, a 1,4-butyl or 1,6-hexyl group is understood to mean that a hydrogen atom is missing at positions 1 and 4, or 1 and 6, respectively, and the group is chemically bonded via these atoms. The "1,4-butyl or 1,6-hexyl group" can also be referred to as a "1,4-butanediyl" or "1,6-hexanediyl group" in this context.

[0059] In the event that mixtures of different starting diisocyanates are used, it is very particularly preferred that < 30 wt.%, preferably < 10 wt.% and particularly preferably > 0 to < 5 wt.% of the total starting diisocyanates used are cycloaliphatic diisocyanates and the remainder are aliphatic diisocyanates.

[0060] Suitable hydroxy-functional compounds for preparing the polyallophanate polyisocyanates for the polyisocyanate mixture according to the invention are, for example, any mono- or polyhydric alcohols having up to 14 carbon atoms, preferably 2 to 6 carbon atoms, such as the mono- or polyhydric alcohols mentioned above as suitable hydroxy-functional catalyst solvents, as well as tetrahydrofurfuryl alcohol, the isomeric pentanediols, hexanediols, heptanediols and octanediols, 1,10-decanediol, 1,2- and 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4,4'-(1-methylethylidene)-biscyclohexanol, 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 but also simple ester alcohols such as hydroxypivalic acid neopentyl glycol ester.

[0061] Suitable hydroxy-functional compounds for the preparation of polyallophanate polyisocyanates are also the known higher molecular weight polyhydroxyl compounds of the polyester, polycarbonate, polyester carbonate or polyether type, in particular those in the molecular weight range 200 to 2000 g / mol.

[0062] Polyester polyols suitable as hydroxy-functional compounds are, for example, those having an average molecular weight, calculable from functionality and hydroxyl number, of 200 to 4000 g / mol, preferably of 250 to 2500 g / mol, with a hydroxyl group content of 1 to 21% by weight, preferably 2 to 18% by weight, as can be prepared in a manner known per se by reacting polyhydric alcohols, for example those mentioned above having 2 to 14 carbon atoms, with sub-stoichiometric amounts of polybasic carboxylic acids, corresponding carboxylic anhydrides, corresponding polycarboxylic acid esters of lower alcohols or lactones.

[0063] The acids or acid derivatives used to produce the polyester polyols can be aliphatic, cycloaliphatic, and / or aromatic in nature and can optionally be substituted, e.g., by halogen atoms, and / or unsaturated. Examples of suitable acids include polybasic carboxylic acids with a molecular weight range of 118 to 300 g / mol or their derivatives, such as succinic acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic acid, maleic acid, maleic anhydride, dimeric and trimeric fatty acids, dimethyl terephthalate, and terephthalic acid bisglycol ester.

[0064] Any mixtures of these starting compounds mentioned as examples can also be used to produce the polyester polyols.

[0065] A type of polyester polyol that can be used alternatively as a hydroxy-functional compound are those that can be prepared in a conventional manner from lactones and simple polyhydric alcohols, such as those mentioned above as examples, as starter molecules by ring opening. Suitable lactones for the preparation of these polyester polyols are, for example, β-propiolactone, γ-butyrolactone, δ- and δ-valcrolactone, ε-caprolactone, 3,5,5- and 3,3,5-trimethylcaprolactone or any mixtures of such lactones. Polyhydroxyl compounds of the polycarbonate type that are suitable as hydroxy-functional compounds are, in particular, the known polycarbonate diols that can be prepared, for example, by reacting dihydric alcohols, for example those mentioned above as examples in the list of polyhydric alcohols with a molecular weight range of 62 to 400 g / mol, with diaryl carbonates, such as, for example, diphenyl carbonate, dialkyl carbonates, such as, for example,Dimethyl carbonate or phosgene can be produced.

[0066] Polyhydroxyl compounds of the polyester carbonate type suitable as hydroxyfunctional compounds are in particular the diols containing ester groups and carbonate groups known per se, as can be obtained, for example, according to the teaching of DE-A 1 770 245 or WO 03 / 002630 by reacting dihydric alcohols with lactones of the type mentioned above by way of example, in particular s-caprolactone, and subsequently reacting the resulting polyester diols with diphenyl carbonate or dimethyl carbonate.

[0067] Polyether polyols suitable as hydroxyfunctional compounds are, in particular, those with an average molecular weight, calculated from functionality and hydroxyl number, of 200 to 2000 g / mol, preferably 250 to 1000 g / mol, and a hydroxyl group content of 1.6 to 25 wt. %, preferably 3.6 to 20 wt. %, as are accessible in a conventional manner by alkoxylation of suitable starter molecules. To prepare these polyether polyols, any polyhydric alcohols, such as the simple polyhydric alcohols having 2 to 14 carbon atoms described above, can be used as starter molecules. Alkylene oxides suitable for the alkoxylation reaction are, in particular, ethylene oxide and propylene oxide, which can be used in any order or as a mixture in the alkoxylation reaction.

[0068] Suitable polyether polyols also include the known polyoxytetramethylene glycols, such as those obtained, for example, by polymerizing tetrahydrofuran according to H. Meerwein et al., Angew. Chem. 72, 1960, 927-934. However, the use of polyether polyols is not preferred.

[0069] Preferred hydroxyfunctional compounds are the above-mentioned simple polyhydric alcohols, ester or ether alcohols, with a molecular weight range of 62 to 400 g / mol. Particular preference is given to the diols and / or triols with 2 to 6 carbon atoms mentioned above in the list of simple polyhydric alcohols. Very particularly preferred hydroxyfunctional compounds are 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and / or 1,1,1-trimethylolpropane. The use of 1,1,1-trimethylpropane is particularly preferred.

[0070] In a further preferred embodiment, the polyallophanate 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 > 2 and < 6 in the presence of a catalyst.

[0071] The hydroxy-functional compound preferably 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 such alcohols can also be used.

[0072] Alternatively, the at least one polyallophanate polyisocyanate is preferably obtained by oligomerizing 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 such alcohols can also be used.

[0073] Preferably, the at least one polyallophanate polyisocyanate is obtained by oligomerizing at least one aliphatic diisocyanate having a molecular weight of > 140 to < 400 g / mol, preferably 1,6-diisocyanatohexane (HDI), and 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 such alcohols can also be used.

[0074] The starting diisocyanates and hydroxy-functional compounds are preferably reacted in an equivalent ratio of isocyanate groups to hydroxyl groups of 4:1 to 200:1, preferably of 5:1 to 50:1 and particularly preferably 5:1 to 25:1, in the presence of at least one suitable catalyst of the type mentioned.

[0075] The reaction to produce the polyallophanate polyisocyanate can be carried out uncatalyzed as a thermally induced allophanatization. However, suitable catalysts are preferably used to accelerate the reaction. Suitable catalysts for the reaction include, for example, the catalysts listed in WO 2019 / 061019 A1 on page 11, line 13 to page 13, line 11. They are added either as such or dissolved in a suitable organic solvent to accelerate the formation of the allophanate groups. Preferred catalyst solvents are those that contain isocyanate-reactive groups and can be incorporated into the polymer accordingly. These are, for example, mono- or polyhydric alcohols such as methanol, ethanol, «-propanol, isopropanol, «-butanol, «-hexanol, 2-ethyl-l-hexanol, ethylene glycol, propylene glycol, isomers of butanediol, 2-ethyl-l,3-hexanediol, glycerol, ether alcohols such as l-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 glycols, polypropylene glycols, mixed polyethylene-polypropylene glycols and their monoalkyl ethers, ester alcohols such as ethylene glycol monoacetate, propylene glycol monolaurate, glycerol diacetate, glycerol monobutyrate or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, unsaturated alcohols such as allyl alcohol, 1,1-dimethylallyl alcohol or oleyl alcohol, araliphatic alcohols such as benzyl alcohol or monosubstituted amides such as N-methylformamide, N-methylacetamide, cyanoacetamide or 2-pyrrolidinone or mixtures such solvents.,

[0076] The reaction is preferably carried out under an inert gas atmosphere at a temperature in the range from 0 °C to 150 °C, preferably in the range between 40 °C and 130 °C and particularly preferably between 70 °C and 120 °C.

[0077] Once the desired degree of conversion is reached, the reaction is stopped. This can be done, for example, by cooling the reaction mixture. Preferably, stopping is done by adding a catalyst poison and, optionally, subsequently heating the reaction mixture to a temperature above 80 °C.

[0078] Suitable catalyst poisons (stoppers) are known to the person skilled in the art. These include, for example, hydrochloric acid, phosphoric acid, phosphonic acid, carboxylic acid chlorides such as acetyl chloride, benzoyl chloride or isophthaloyl dichloride, sulfonic acids or sulfonic acid esters such as methanesulfonic acid esters, p-toluenesulfonic acid, trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, dodecylbenzenesulfonic acid, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, mono- or dialkyl phosphates such as tridecyl phosphate, dibutyl phosphate, dioctyl phosphate, or silylated acids such as trimethylsilyl methanesulfonate, trifluoromethanesulfonic acid trimethylsilyl ester,

[0079] Tris(trimethylsilyl) phosphate or diethyl(trimethylsily) phosphate.

[0080] The amount of catalyst poison required to stop the reaction depends largely on the amount of catalyst used. In principle, an equivalent amount of the inhibitor is required, but since part of the catalyst is usually deactivated by other means, a smaller amount of inhibitor may be sufficient.

[0081] The catalyst poison can also be added as such or in solution, with the catalyst solvents listed above being suitable solvents. In addition to these solvents, the starting isocyanates can also be used as solvents for the catalyst poisons.

[0082] After the reaction has ended, the starting diisocyanate is separated from the reaction product. This is preferably carried out by distillation, for example at a pressure below 5 mbar, preferably below 1 mbar and particularly preferably below 0.5 mbar and for example at a temperature in the range from 100 to 200 °C, preferably in the range from 120 to 180 °C. The residual content of monomeric diisocyanate after distillation is preferably <0.50 wt.%, particularly preferably <0.3 wt.% and particularly preferably <0.10 wt.%. The proportion of monomeric diisocyanate in the at least one polyallophanate polyisocyanate can be greater than 0.10 wt.%, as long as it is less than 0.10 wt.% in the polyisocyanate mixture according to the invention.

[0083] The polyallophanate polyisocyanate preferably has an average isocyanate functionality >4 and / or a weight-average molecular weight of >3000 g / mol, determined according to EN ISO 13885-1:2021-11.

[0084] In this case, the average isocyanate functionality of the polyisocyanurate polyisocyanates at least contained in the polyisocyanate is determined according to the following formula:

[0085] Mn(GPC)

[0086] F(GPC) = >

[0087] 100 x 42

[0088] %NCO(Titr.)

[0089] Wherein the isocyanate group content is given as wt.% and is determined titrimetrically according to DIN EN ISO 11909:2007-05 and the number average molecular weight is determined by GPC according to DIN EN ISO 13885-1:2021-11 using polystyrene as standard and tetrahydrofuran as eluent.

[0090] The present invention further provides a process for producing a polyisocyanate mixture according to the invention, characterized in that at least one polyisocyanurate polyisocyanate and at least one polyallophanate 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 polyallophanate polyisocyanate has a weight-average molecular weight of > 3000 g / mol, determined according to DIN EN ISO 13885-1:2021-11.

[0091] Mixing can be carried out by any method and in any sequence. If desired, a suitable solvent can be added to the process. Suitable solvents are those generally known to those skilled in the art as solvents in the coating field and are cited as examples in this text.

[0092] In a preferred embodiment of the process according to the invention, 30-70 parts by weight of the at least one polyisocyanurate polyisocyanate and 70-30 parts by weight of the at least one polyallophanate polyisocyanate are mixed. One and / or both polyisocyanates may contain one or more of the solvents mentioned in the present text, preferably at least butyl acetate, for the mixing. If one or more solvents are used, it is particularly preferred that the polyallophanate polyisocyanate be present in the solvent.

[0093] The present invention further provides a coating composition comprising either at least one polyisocyanate mixture according to the invention and at least one binder reactive towards isocyanate groups or comprising at least one polyisocyanate mixture obtainable or produced by a process according to claim 8 or 9 and at least one binder reactive towards isocyanate groups.

[0094] In a further preferred embodiment, the inventive

[0095] Coating composition comprising at least one binder reactive towards isocyanate groups in a component A) and at least one inventive

[0096] Polyisocyanate mixture in a component B) or the at least one polyisocyanate mixture, obtainable or prepared by a process according to claim 8 or 9, in a component B). Such a preferred embodiment is also referred to below as a two-component system.

[0097] All compounds known to the person skilled in the art which have an average OH or NH functionality of at least 1.5 can be used as "isocyanate-reactive binders." These can be, for example, low-molecular-weight diols (e.g., 1,2-ethanediol, 1,3- or 1,2-propanediol, 1,4-butanediol), triols (e.g., glycerol, trimethylolpropane), and tetraols (e.g., pentaerythritol), short-chain polyamines, but also polyhydroxy compounds such as polyether polyols, polyester polyols, polyurethane polyols, polysiloxane polyols, polycarbonate polyols, polyether polyamines, polybutadiene polyols, polyacrylate polyols, and / or polymethacrylate polyols, as well as copolymers thereof, hereinafter referred to as polyacrylate polyols.

[0098] Regardless of whether it is the coating composition according to the invention or the preferred two-component system according to the invention, it is further preferred that the at least one binder reactive towards isocyanate groups is a polyhydroxy compound, preferably a polyether polyol, polyester polyol, polyurethane polyol, polysiloxane polyol, polycarbonate polyol, polyether polyamine, polybutadiene polyol, polyacrylate polyol and / or polymethacrylate polyol and copolymers thereof and particularly preferably a polycarbonate polyol, polyester polyol, polyacrylate polyol or any mixtures of the aforementioned.

[0099] Regardless of whether it is the coating composition according to the invention or the preferred two-component system according to the invention, it is further preferred that the at least one binder reactive towards isocyanate groups comprises at least one hydroxy-functional compound having a hydroxyl group content of > 2.0 wt.%, preferably > 3.0 wt.% and particularly preferably > 3.5 wt.%, based on the solids content of the binder reactive towards isocyanate groups.

[0100] Preferably, the ratio of the polyisocyanate mixture according to the invention to compounds reactive toward isocyanate groups in the coating composition according to the invention or the two-component system according to the invention, based on the molar amounts of isocyanate groups to NCO-reactive groups, is from 0.8 to 1.0 to 2.0 to 1.0. A ratio of 1.0 to 1.0 to 1.5 to 1.0 is particularly preferred. A ratio of 1.05 to 1.0 to 1.25 to 1.0 is most preferred.

[0101] The polyhydroxy compounds preferably have mass-average molecular weights Mw > 500 Dalton, measured by gel permeation chromatography (GPC) against a polystyrene standard, particularly preferably between 800 and 100,000 Dalton, in particular between 1,000 and 50,000 Dalton.

[0102] The polyhydroxy compounds preferably have an OH number of 30 to 400 mg KOH / g, especially between 100 and 300 mg KOH / g. The hydroxyl number (OH number) indicates how many mg of potassium hydroxide are equivalent to the amount of acetic acid bound by 1 g of substance during acetylation. For the determination, the sample is boiled with acetic anhydride and pyridine, and the resulting acid is titrated with potassium hydroxide solution (DIN 53240-2).

[0103] The glass transition temperatures, measured by DSC measurements according to DIN-EN-ISO 1 1357-2, of the polyhydroxy compounds are preferably between -150 and 100 °C, particularly preferably between -120 °C and 80 °C.

[0104] Polyether polyols can be prepared in a conventional manner by alkoxylation of suitable starter molecules under base catalysis or using double metal cyanide compounds (DMC compounds). Suitable starter molecules for the production of polyether polyols include, for example, simple, low-molecular-weight polyols, water, organic polyamines with at least two NH bonds, or any mixtures of such starter molecules.

[0105] Preferred starter molecules for the preparation of polyether polyols by alkoxylation, particularly by the DMC process, are, in particular, simple polyols such as ethylene glycol, propylene glycol-1,3-butanediol and butane-1,4-diol, hexane-1,6-diol, neopentyl glycol, 2-ethylhexane-1,3-diol, glycerol, trimethylolpropane, pentaerythritol, as well as low-molecular-weight, hydroxyl-containing esters of such polyols with dicarboxylic acids of the type exemplified below, or low-molecular-weight ethoxylation or propoxylation products of such simple polyols, or any mixtures of such modified or unmodified alcohols. Alkylene oxides suitable for alkoxylation are, in particular, ethylene oxide and / or propylene oxide, which can be used in any order or as a mixture during the alkoxylation.

[0106] Suitable polyester polyols are described, for example, in EP-A-0 994 1 17 and EP-A-1 273 640. Polyester polyols can be prepared in a known manner by polycondensation of low molecular weight polycarboxylic acid derivatives, such as 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, dimer fatty acid, trimer fatty acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, citric acid or trimellitic acid, with low molecular weight polyols, such as ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol, trimethylolpropane, 1,4-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, butanetriol-1,2,4, 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 s-caprolactone. Furthermore, hydroxycarboxylic acid derivatives, such as lactic acid, cinnamic acid, or co-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 produced, for example, by complete ring opening of epoxidized triglycerides of an at least partially olefinically unsaturated fatty acid-containing fat mixture with one or more alcohols having 1 to 12 carbon atoms, followed by partial transesterification of the triglyceride derivatives to form alkyl ester polyols having 1 to 12 carbon atoms in the alkyl radical.

[0107] Polyurethane polyols are preferably prepared by reacting polyester polyol prepolymers with suitable di- or polyisocyanates and are described, for example, in EP-A-1 273 640. Suitable polysiloxane polyols are described, for example, in WO-A-01 / 09260, wherein the polysiloxane polyols listed therein can preferably be used in combination with other polyhydroxy compounds, in particular those with higher glass transition temperatures.

[0108] The polyacrylate polyols particularly preferred according to the invention are generally copolymers and preferably have mass-average molecular weights Mw between 1,000 and 20,000 Daltons, in particular between 1,500 and 10,000 Daltons, measured by gel permeation chromatography (GPC) against a polystyrene standard. The glass transition temperature of the copolymers is generally between -100 and 100 °C, in particular between -50 and 80 °C (measured by DSC measurements according to DIN EN ISO 11357-2).

[0109] The polyacrylate polyols preferably have an OH number of 60 to 250 mg KOH / g, in particular between 70 and 200 mg KOH / g, and an acid number between 0 and 30 mg KOH / g. The acid number indicates the number of mg of potassium hydroxide consumed to neutralize 1 g of the respective compound (DIN EN ISO 21 14).

[0110] The preparation of suitable polyacrylate polyols is known per se to the person skilled in the art. They are prepared by radical polymerization of olefinically unsaturated monomers containing hydroxyl groups or by radical copolymerization of olefinically unsaturated monomers containing hydroxyl groups with, if appropriate, other olefinically unsaturated monomers, such asEthyl 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, isobutyl acrylate, isobutyl methacrylate or in particular cyclohexyl acrylate and / or cyclohexyl methacrylate. Suitable olefinically unsaturated monomers containing hydroxyl groups are in particular 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-.

[0111] Hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 3-

[0112] Hydroxybutyl acrylate, 3-hydroxybutyl methacrylate and in particular 4-hydroxybutyl acrylate and / or 4-hydroxybutyl methacrylate.

[0113] Further monomer building blocks for the polyacrylate polyols that can be used are vinyl aromatic hydrocarbons, such as vinyltoluene, alpha-methylstyrene or in particular styrene, amides or nitriles of acrylic or methacrylic acid, vinyl esters or vinyl ethers, and in minor amounts, in particular acrylic and / or methacrylic acid.

[0114] 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 and particularly preferably 5 to 10% by weight, based on the total amount of polyacrylate polyol, of at least one polyester polyol.

[0115] Both the coating composition according to the invention and component A) and / or component B) of the two-component system according to the invention can further contain conventional auxiliaries and additives in effective amounts. Effective amounts for solvents are preferably up to 150% by weight, particularly preferably up to 100% by weight, and in particular up to 70% by weight, based in each case on the non-volatile constituents of the two-component system according to the invention or the coating composition according to the invention. Effective amounts of other additives are preferably up to 25% by weight, particularly preferably up to 10% by weight, and in particular up to 5% by weight, again based in each case on the non-volatile constituents.

[0116] Examples of suitable auxiliaries and additives are, in particular, light stabilizers such as UV absorbers and sterically hindered amines (HALS), furthermore stabilizers, fillers and anti-settling agents, defoamers, anti-crater and / or wetting agents, leveling agents, film-forming aids, reactive diluents, solvents, substances for rheology control, slip additives and / or components which prevent soiling and / or improve the cleanability of the cured coatings, furthermore matting agents.

[0117] The use of light stabilizers, particularly UV absorbers such as substituted benzotriazoles, S-phenyltriazines, or oxalanilides, as well as sterically hindered amines, particularly those with 2,2,6,6-tetramethylpiperidyl structures – referred to as HALS – is described as an example in A. Valet, Lichtschutzmittel für Lacke (Light Stabilizers for Paints), Vincentz Verlag, Hanover, 1996. Stabilizers such as radical scavengers and other polymerization inhibitors such as sterically hindered phenols stabilize paint components during storage and are intended to prevent discoloration during curing. Acidic stabilizers such as alkyl-substituted partial phosphoric acid esters can also be considered for component B).

[0118] The coating composition according to the invention or the two-component system according to the invention may further contain pigments, dyes and / or fillers. The pigments used therefor, including metallic or other effect pigments, dyes and / or fillers, are known to the person skilled in the art.

[0119] Preferred fillers are those compounds that do not negatively affect the appearance of the coating. Examples include nanoparticles based on silicon dioxide, aluminum oxide, or zirconium oxide. For further information, please refer to the Römpp Encyclopedia "Lacke und Druckfarben" (Lacke and Printing Inks), Georg Thieme Verlag, Stuttgart, 1998, pages 250 to 252.

[0120] 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, the addition of anti-settling agents may be useful to prevent separation of the components during storage.

[0121] Wetting and leveling agents improve the surface wetting and / or leveling of coatings. Examples include fluorosurfactants, silicone surfactants, and special polyacrylates. Rheology-controlling additives are important for maintaining the properties of the coating composition or the coating itself.of the two-component system during application and in the flow phase on the substrate and are known, for example, from patent specifications WO 94 / 22968, EP-A-0 276 501, EP-A-0 249 201 or WO 97 / 12945; crosslinked polymeric microparticles, as disclosed, for example, in EP-A-0 008 127; inorganic sheet silicates such as aluminum-magnesium silicates, sodium-magnesium and sodium-magnesium-fluoro-lithium sheet silicates of the montmorillonite type; silicas such as Aerosil®; or synthetic polymers with ionic and / or associative groups such as polyvinyl alcohol, poly(meth)acrylamide, poly(meth)acrylic acid, polyvinylpyrrolidone, styrene-maleic anhydride or ethylene-maleic anhydride copolymers and their derivatives or hydrophobically modified ethoxylated urethanes or polyacrylates.

[0122] The coating composition according to the invention or the two-component system according to the invention can be used solvent-free, but preferably contains at least one solvent in component A) and / or component B).

[0123] Suitable solvents should be used in a manner known to those skilled in the art, tailored to the coating composition or two-component system used and the application method. Solvents should dissolve the components used, promote their mixing and avoid incompatibilities. Furthermore, during application and curing, they should leave the coating tailored to the ongoing crosslinking reaction (TI) so that a solvent-free coating is created with the best possible appearance and without defects such as popping or pinholes. Solvents used in two-component technology are particularly suitable. 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, aromatics such as xylene or solvent naphtha such as from Exxon-Chemie, as well as mixtures of the solvents mentioned.

[0124] The coating composition according to the invention or the two-component system according to the invention can be used very well for coating a substrate.

[0125] A further subject of the present invention is therefore the use of a polyisocyanate mixture according to the invention or a 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 body, in particular of a vehicle, or parts thereof.

[0126] In addition to such a use, the invention further provides a process for producing a coating, preferably a refinishing coating, on a substrate, comprising the following steps: a) providing an optionally pretreated substrate; b) applying at least one coating composition according to the invention; c) drying the coating composition at RT or with forced heat supply at max. 60°C

[0127] For use in step a) of the above-mentioned processes according to the invention, the substrates can be uncoated or coated. Coatings can be, for example, original automotive finishes before they are used in the process according to the invention. Examples of primers as used in automotive refinishing are solvent-borne or water-based primers, primer fillers or sanding fillers, as well as basecoats known to the person skilled in the art, for example from A. Goldschmidt, H. Streitberger, "BASF Handbook of Painting Technology", Vincentz-Verlag, Hanover, Germany, 2002. Corresponding products are available, for example, from BASF Coatings GmbH, Münster, Germany under the name "Glasurit" or from Axalta Coatings Systems Germany GmbH, Wuppertal, Germany under the name "Spies Hecker Permasolid / Permahyd".

[0128] Suitable substrates include, for example, substrates comprising one or more materials, in particular so-called composite materials. A substrate composed of at least two materials is referred to as a composite material according to the invention. Suitable materials are preferably steel, aluminum, or galvanized surfaces. Within the scope of the invention, the term "plastic" also includes fiber-reinforced plastics, such as glass- or carbon-fiber-reinforced plastics, and plastic blends composed of at least two or more plastics.

[0129] Examples of plastics suitable for use in 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 7728T1). These can also be in the form of films or as glass- or carbon-fiber-reinforced plastics.

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

[0131] According to a further embodiment of the method according to the invention, the substrate comprises metal, in particular the substrate can consist of 80 wt.%, 70 wt.%, 60 wt.%, 50 wt.%, 25 wt.%, 10 wt.%, 5 wt.%, 1 wt.% of metal.

[0132] According to one embodiment of the invention, the substrate to be provided in step a) is a body or parts thereof comprising one or more of the aforementioned materials. Preferably, the body or parts thereof comprise one or more materials selected from metal, plastic, or mixtures thereof.

[0133] The coating composition according to the invention or the two-component system according to the invention in step b) of the process according to the invention can be applied from solution. Suitable application methods include, for example, printing, brushing, rolling, pouring, dipping, fluidized-bed processes, and / or spraying, such as compressed air spraying, airless spraying, high-speed rotation, or electrostatic spray application (ESTA), optionally combined with hot spray application, such as hot air spraying. Application by spraying, such as compressed air spraying, airless spraying, high-speed rotation, or electrostatic spray application (ESTA), optionally combined with hot spray application, such as hot air spraying, is particularly preferred.

[0134] The coating composition or two-component system to be applied in step b) can be applied after components A) and B) have been mixed or mixed immediately during application. In the first case, the mixed two-component system has a limited shelf life, the so-called pot life, since the crosslinking reaction progresses slowly after mixing. In the second case, the advantageous effect of the extended pot life is evident, for example, in an improved paint appearance, since the coating composition or two-component system according to the invention can form a uniform film on the substrate. It has proven particularly practical for the process according to the invention if curing in step c) takes place at a substrate temperature of room temperature up to a maximum of 60°C.

[0135] Drying in step c) of the process according to the invention is carried out in less than 60 minutes at 60°C, most preferably in less than 30 minutes. Alternatively, drying at room temperature can be carried out over several hours.

[0136] Drying, as used here, means that the coating systems have reached dust drying (TI). Tested according to DIN 53 150:2002-09

[0137] The process according to the invention therefore enables the joint 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 enable a processing time of more than 30 minutes in the painting process, exhibit good gloss retention of the coating of more than 75 units gloss at 20° after drying, and enable easy hand mixing by stirring in by hand with a stirring rod. The easy hand mixing (here also referred to as good incorporation properties) is a further advantage of the polyisocyanate mixture according to the invention. This results in its particularly preferred suitability in the field of craft applications, such as repair painting but also wood painting.

[0138] The invention further relates to a coating which has been produced or can be produced by the process according to the invention.

[0139] The invention further provides a coated substrate obtainable or produced by the process according to the invention, wherein the optionally pretreated substrate is preferably a body, in particular of a vehicle, or parts thereof and / or preferably comprises one or more materials selected from metal, plastic, 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.

[0140] According to a preferred embodiment of the invention, the substrate coated with the coating composition according to the invention is a body, in particular of a vehicle or parts thereof, or a piece of furniture or other materials made of wood. The vehicle can be constructed from one or more materials. Suitable materials include, for example, metal, plastic, or mixtures thereof. The vehicle can be any vehicle known to those skilled in the art. For example, the vehicle can be a motor vehicle, truck, motorcycle, scooter, bicycle, or the like. The vehicle is preferably a motor vehicle and / or truck, and is particularly preferably a motor vehicle.According to a further preferred embodiment of the invention, the substrate coated with the coating according to the invention is a body or parts thereof comprising one or more materials selected from metal, plastic, or mixtures thereof. The invention is explained in more detail below using examples, without being limited to them.

[0141] Examples:

[0142] Unless otherwise stated, all percentages are based on weight.

[0143] The NCO content was determined titrimetrically according to DIN EN ISO 11909:2007-05.

[0144] The residual monomer contents were measured according to DIN EN ISO 10283:2007-11 using gas chromatography with an internal standard.

[0145] 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.

[0146] Flow times were determined according to DIN EN ISO 2431:2012-03 using a flow cup with a 4 mm nozzle.

[0147] The drying properties of the coating systems were determined according to DIN 53 150:2002-09.

[0148] The gloss of the resulting coatings was measured reflectometrically according to DIN EN ISO 2813: 1999-06 at a 20° angle.

[0149] The determination of pendulum damping according to König was carried out according to DIN EN ISO 1522:2007-04 on glass plates.

[0150] 13C NMR spectra were recorded using a Bruker AV III HD 600 NMR spectrometer with probe head Z150361 001 (CP BBO 600SS3 BB-H&F-05 ZE T). 512 scans were performed with a repetition time (DI) of 4 s and an acquisition time (AQ) of 1.57 s.

[0151] Molecular weights were measured by gel permeation chromatography according to DIN EN ISO 13885-1:2021-11. Four columns (2x PSS SDV 50A, 5p, 2x PSS SDV 100A, 5p) were used.

[0152] To test the coatings for solvent resistance, small amounts of the solvents xylene, 1-methoxypropyl-2-acetate, ethyl acetate, and acetone were placed in test tubes and a cotton ball placed over the opening to create a solvent-saturated atmosphere inside the test tubes. The test tubes were then placed on the surface of the coatings applied to glass with the cotton ball and left there for 1 or 5 minutes. After wiping off the solvent, the film was tested for destruction / softening / loss of adhesion and rated (0 = no change, 5 = film completely dissolved). The ratings for the four solvents are given in the following order: xylene, 1-methoxypropyl-2-acetate, ethyl acetate, and acetone as four consecutive numbers. The gasoline resistance test was performed analogously using premium gasoline E10. Polyisocyanate 1 (biuret polyisocyanate)

[0153] Biuret group-containing HDI polyisocyanate, prepared by the process of EP-B 1158013 (Example 2b) by continuously reacting 667 parts of HDI with 27 parts of hexamethylenediamine (HDA) in the presence of one part by weight of dibutyl phosphate as catalyst at a temperature of 280°C. Following 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 characteristics.

[0154] NCO content: 16.4% monomeric HDI: 0.32%

[0155] Viscosity (23°C): 160 mPas

[0156] Allophanate group content: 0 mol%

[0157] Isocyanurate group content: < 5 mol-%

[0158] Biuret group content: > 95 mol%

[0159] Weight average molecular weight Mw: 1420 g / mol

[0160] Polyisocyanate 2 (polyisocyanurate polyisocyanate)

[0161] HDI polyisocyanate containing isocyanurate groups, prepared by catalytic trimerization of HDI based on Example 11 of EP-A 330 966, except that 2-ethylhexanol was used as the catalyst solvent instead of 2-ethyl-1,3-hexanediol, and the reaction was stopped at an NCO content of the crude mixture of 42.5% by adding dibutyl phosphate. Unreacted HDI was then removed by thin-film distillation at a temperature of 130 °C and a pressure of 0.2 mbar. The resulting polyisocyanurate polyisocyanate had the following characteristics.

[0162] NCO content: 23.0% monomeric HDI: 0.08%

[0163] Viscosity (23°C): 1210 mPas

[0164] Allophanate group content: 5 mol%

[0165] Isocyanurate group content: 95 mol-%

[0166] Weight average molecular weight Mw: 760 g / mol

[0167] Polyisocyanate 3 (polyisocyanurate polyisocyanate)

[0168] HDI polyisocyanate containing isocyanurate groups, prepared by catalytic trimerization of HDI based on Example 11 of EP-A 330 966, except that the reaction was stopped at an NCO content of the crude mixture of 40% by adding dibutyl phosphate. Unreacted HDI was then separated 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 wt.% and had the following characteristics.

[0169] NCO content: 19.6% monomeric HDI: 0.08%

[0170] Viscosity (23°C): 500 mPas

[0171] Allophanate group content: 8 mol%

[0172] Isocyanurate group content: 92 mol-%

[0173] Weight average molecular weight Mw: 1120 g / mol

[0174] Polyisocyanat 4 (Polyisocyanurat / Allophanatpolyisocyanat)

[0175] 100 parts of hexamethylene diisocyanate (HDI) were initially charged and heated to 105 °C. At this temperature, 10 parts of trimethylolpropane were added with stirring. After the urethanization reaction was complete, the reaction temperature was lowered to 95 °C. The trimerization and allophanatization reaction was then initiated by adding a 0.5% trimethylbenzylammonium hydroxide solution in 2-ethylhexanol. When an NCO value of 36% was reached, the reaction was terminated by adding a stopper solution (10% dibutyl phosphate in HDI) in a weight ratio of 100 parts of catalyst solution to 3 parts of stopper solution. The mixture was stirred for a further 30 minutes at 95 °C, after which the remaining monomeric HDI was removed in a short-path evaporator at 140 °C and 0.1 mbar. The resulting polyisocyanate was diluted with butyl acetate to 80 wt.% polyisocyanate content and had the following characteristics.

[0176] NCO content: 15.4% monomeric HDI: 0.07%

[0177] Viscosity (23°C): 500 mPas

[0178] Allophanate group content: 70 mol%

[0179] Isocyanurate group content: 30 mol-%

[0180] Weight average molecular weight Mw: 3140 g / mol

[0181] Polyisocyanate mixture 5 (according to the invention)

[0182] 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 characteristics:

[0183] NCO content: 17.6% monomeric HDI: 0.06%

[0184] Viscosity (23°C): 128 mPas Allophanate group content: 28 mol-%

[0185] Isocyanurate group content: 72 mol-%

[0186] Weight average molecular weight Mw: 1520 g / mol

[0187] Polyisocyanate mixture 6 (according to the invention)

[0188] 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 characteristics:

[0189] NCO content: 16.7% monomeric HDI: 0.07%

[0190] Viscosity (23°C): 267 mPas

[0191] Allophanate group content: 47 mol%

[0192] Isocyanurate group content: 53 mol-%

[0193] Weight average molecular weight Mw: 2305 g / mol

[0194] Examples 1, 2, 3, 4 and 5 (coating compositions and paint testing; according to the invention and comparison)

[0195] Varying parts by weight of a commercially available polyester polyol (Desmophen® XP 775; Covestro AG, Leverkusen, DE) with a solids content of 75% by weight and an OH content (based on delivery form) of 9.5%, corresponding to an equivalent weight of 180 g / eq OH, were mixed with 0.80 parts by weight of a 50% solution of a commercially available 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 (Byk 331, Byk-Chemie GmbH), 2.50 parts by weight of a 1% solution of Dibutyltin dilaurate (DBTL) is added to butyl acetate and mixed homogeneously by intensive stirring.

[0196] Different parts by weight of a solvent mixture consisting of equal parts by weight of butyl acetate, MPA and xylene are then homogeneously incorporated at room temperature by intensive stirring in order to obtain a non-volatile content of 56% by weight in the coatings to be processed.

[0197] Subsequently, varying parts by weight of the polyisocyanates 1, 3, 4 and the polyisocyanate mixtures 5 and 6 were also stirred into butyl acetate, corresponding to an equivalent ratio of isocyanate groups to hydroxyl groups of 1:1 as a crosslinking component, by hand using a stirrer. Coating compositions 1 to 5 were applied to glass plates using a film applicator in a wet film thickness of approximately 150 μm, cured within 30 minutes at 60°C, and aged for 16 hours at 60°C.

[0198] Table 1 below shows the compositions of the coating compositions 1 to 5 in parts by weight, Table 2 shows the results of the application tests of the obtained

[0199] Coatings in comparison.

[0200] Table 1: Comparative Examples 1, 2 and 3 and Examples 4 and 5 according to the invention -

[0201] Composition of the coating agents

[0202] Table 2: Comparative Examples 1, 2 and 3 and inventive Examples 4 and 5 -

[0203] Paint technical properties

[0204] 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 do not have a satisfactory processing time, as the viscosity increases significantly after just 30 minutes. Conversely, an isocyanurate-based system (Comparative Example 2) achieves a good processing time but only poor gloss.

[0205] Chemical resistance also does not quite reach the high level of the comparison systems, especially against acetone as a test substance.

[0206] Only the polyisocyanate mixtures according to the invention lead to high-solids coating systems (non-volatile content (NF) during processing of >56 wt.%), which have a long processing time and good appearance while being highly resistant to chemicals.

Claims

Polyisocyanate mixture containing at least one polyisocyanurate polyisocyanate and at least one polyallophanate polyisocyanate, wherein the polyisocyanate mixture has a content of monomeric diisocyanates of < 0.10 wt.%, determined according to DIN EN ISO 10283:2007-11 by gas chromatography with an internal standard, an isocyanurate group content of > 40 mol-% to < 85 mol-%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture, and an allophanate group content of > 15 mol-% to < 60 mol-%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture.Polyisocyanate mixture according to claim 1, characterized in that it has an isocyanurate group content of > 45 mol% to < 80 mol%, preferably > 50 mol% to < 75 mol% and particularly preferably > 53 mol% to < 72 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture, and / or an allophanate group content of > 20 mol% to < 55 mol%, preferably > 25 mol% to < 50 mol% and particularly preferably > 28 mol% to < 47 mol%, determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture. Polyisocyanate mixture according to claim 1 or 2, characterized in that it has a weight-average molecular weight of > 1000 g / mol to < 3000 g / mol, preferably from > 1300 g / mol to < 2700 g / mol and particularly preferably from > 1500 g / mol to < 2500 g / mol, determined according to DIN EN ISO 13885-1:2021-11.Polyisocyanate mixture according to one of claims 1 to 3, characterized in that it has a polydispersity of > 1.5 to < 2.5, preferably of > 1.7 to < 2.2, determined according to DIN 55672-1:2016-03. Polyisocyanate mixture according to one of claims 1 to 4, characterized in that the at least one polyallophanate 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. Polyisocyanate mixture according to 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 to one another via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of > 56 to < 316 g / mol, preferably in each case via a 1,4-butyl or 1,6-hexyl group and particularly preferably in each case via a 1,6-hexyl group.

7. Polyisocyanate mixture according to one of claims 1 to 6, characterized in that the at least one polyallophanate polyisocyanate contains one or more allophanate groups which are each chemically bonded to one another via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of > 56 to < 316 g / mol, preferably in each case via a 1,4-butyl or 1,6-hexyl group and particularly preferably in each case via a 1,6-hexyl group.

8. A process for producing a polyisocyanate mixture according to any one of claims 1 to 7, characterized in that at least one polyisocyanurate polyisocyanate and at least one polyallophanate 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 polyallophanate 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 polyallophanate polyisocyanate are mixed.

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

11. Coating composition according to claim 10, characterized in that it contains the at least one binder reactive towards isocyanate groups in a component A) and the at least one polyisocyanate mixture according to one of claims 1 to 7 in a component B) or the at least one polyisocyanate mixture, obtainable or produced according to a process according to claim 8 or 9, in a component B) and / or that the at least one binder reactive towards isocyanate groups is a polyhydroxy compound, preferably a polyether polyol, polyester polyol, polyurethane polyol, polysiloxane polyol, polycarbonate polyol, polyether polyamine, polybutadiene polyol, polyacrylate polyol and / or polymethacrylate polyol and also copolymers thereof and particularly preferably a polyester polyol, polyacrylate polyol or any mixtures of the aforementioned.

12. Coating composition according to one of claims 10 to 11, characterized in that the at least one binder reactive towards isocyanate groups comprises at least one hydroxy-functional compound having a hydroxyl group content of > 2.0 wt.%, preferably of > 3.0 wt.% and particularly preferably of > 3.5 wt.%, based on the solids content of the binder reactive towards isocyanate groups.

13. Use of a polyisocyanate mixture according to any one of claims 1 to 7 or of 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 of a vehicle, or parts thereof.

14. A process for producing a coating on a substrate, comprising the following Steps: a) providing an optionally pretreated substrate; b) applying at least one coating composition according to one of claims 10 to 12; c) curing the coating composition with the application of heat.

15. Coated substrate obtainable or produced by a process according to claim 14, wherein the optionally pretreated substrate is preferably a body, in particular of a vehicle, or parts thereof and / or preferably comprises one or more of the materials selected from metal, plastic or mixtures thereof.

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