Polyisocyanate mixture

Abstract

The present invention relates to a polyisocyanate mixture containing: at least one HDI polyisocyanate M) having a viscosity according to DIN EN ISO 3219:1994-10 at 23°C of 100 to 1600 mPas and comprising allophanate- and / or isocyanurate structures, and at least one PDI polyisocyanate N) in a weight ratio of 80 : 20 to 20 : 80. The invention further relates to the use of the polyisocyanate mixture and to a composition containing the polyisocyanate mixture, to a method for producing a coating on a substrate and to the coated substrate.

Description

[0001] Polyisocyanate mixture

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

[0003] Two-component polyurethane coatings (2K-PUR) have gained importance in a wide variety of applications due to their outstanding technological properties. Polyisocyanates based on linear aliphatic or cycloaliphatic diisocyanates are typically used as crosslinking components for light-resistant, non-yellowing 2K-PUR coatings and paints.

[0004] 2K-PUR coatings, which are crosslinked with aliphatic polyisocyanates, in particular derivatives of hexamethylene diisocyanate (HDI), optionally in combination with polyisocyanates based on cycloaliphatic isophorone diisocyanate (IPDI), provide coatings with high mechanical and chemical resistance and very good appearance.

[0005] Despite the high quality level already achieved by 2K PUR coatings, there is a constant interest in the market for coating systems with ever-improving properties, particularly improved scratch resistance.

[0006] The trend toward more sustainable products has led to increasing demand for bio-based raw materials in recent years, including in the polyurethane sector. This prompted the development of polyisocyanate crosslinkers based on 1,5-diisocyanatopentane (hereinafter also referred to as pentamethylene diisocyanate or PDI), which is accessible from biomass (see, for example, EP-A 3 271 432 and WO 2016 / 169810). PUR coatings and adhesives produced using bio-based PDI polyisocyanates exhibit a similar level of properties to those crosslinked with comparable petrochemical-based HDI polyisocyanates, and are even superior in some applications.

[0007] A serious disadvantage of PDI polyisocyanates, however, is the fact that they exhibit higher viscosities than corresponding HDI derivatives with a comparable oligomer distribution (M. Widemann et al., ACS Sustainable Chem. Eng. 2018, 6, 9753-9759; DOI: http: / / dx.doi.org / 10.1021 / acssuschemeng.8b00758), and their processing generally requires larger amounts of organic solvents. However, the lowest possible content of volatile organic components is desirable, especially in sustainable coating and adhesive systems.

[0008] Especially for applications such as automotive refinishing, there was a need for sustainable polyisocyanate mixtures with sufficiently low viscosities to enable them to be processed in low-solvent or solvent-free form.

[0009] The object of the present invention was therefore to provide sustainable polyisocyanate mixtures which have sufficiently low viscosities to enable them to be processed in low-solvent or solvent-free form and which lead to coatings with improved properties, in particular improved scratch resistance.

[0010] This object is achieved according to the invention by a polyisocyanate mixture, at least one HDI polyisocyanate M) having allophanate and / or isocyanurate structures and having a viscosity at 23°C of 100 to 1600 mPas, determined according to DIN EN ISO 3219:1994-10 at a shear rate of 250 s-1, and at least one PDI polyisocyanate N) in a weight ratio of M) to N) of 80:20 to 20:80.

[0011] According to the invention, the terms "comprising" and "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 as desired, unless the context clearly indicates otherwise.

[0012] "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 polyisocyanate" therefore means, for example, that only one type of polyisocyanate or several different types of polyisocyanates may be present, without specifying the amount of the individual components.

[0013] Numerical values ​​stated without decimal places refer to the full specified value with one decimal place. For example, "99%" stands for "99.0%."

[0014] 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.

[0015] For the purposes of this document, the term "aliphatic" is defined as non-aromatic hydrocarbon groups that are saturated or unsaturated.

[0016] Here, the term "araliphatic" is defined as aliphatic hydrocarbon radicals that are saturated or unsaturated and have at least one aromatic substituent.

[0017] For the purposes of this document, the term "alicyclic" or "cycloaliphatic" is defined as optionally substituted, carbocyclic, or heterocyclic compounds or moieties that are not aromatic (such as cycloalkanes, cycloalkenes, or oxa-, thia-, aza-, or thiazacycloalkanes). Specific examples include cyclohexyl groups, cyclopentyl groups, and their N- or O-heterocyclic derivatives, such as pyrimidine, pyrazine, tetrahydropyran, or tetrahydrofuran.

[0018] In the event that the groups or compounds are disclosed as "optionally substituted" or "substituted," suitable substituents are -F, -Cl, -Br, -I, -OH, -OCH3, OCH2CH3, -O-isopropyl or -on-propyl, -OCF3, -CF3, -S-C1-6-alkyl, and / or (optionally via an attached heteroatom) a linear or branched, aliphatic and / or alicyclic structural unit having 1 to 12 carbon atoms, each acting as a replacement for a carbon-bonded hydrogen atom of the molecule in question. Preferred substituents are halogen (especially -F, -Cl), C1-6-alkoxy (especially methoxy and ethoxy), hydroxy, trifluoromethyl, and trifluoromethoxy, each acting as a replacement for a carbon-bonded hydrogen atom of the molecule in question.

[0019] The general term "polyurethanes" is used hereinafter as a synonym for the multitude of different polymers with, for example, urethane, urea, and / or thiourethane structures that can be produced from polyisocyanates and H-acidic compounds, such as polyols, polyamines, and / or polythiols. The polyisocyanate mixture according to the invention represents a physical blend and thus differs from a polyisocyanate produced purely chemically by direct means, for example, with regard to the oligomer distribution, which can be determined by gel permeation chromatography according to DIN EN ISO 13885-1:2021-11.

[0020] In a first preferred embodiment of the polyisocyanate mixture according to the invention, the polyisocyanates M) and N) are present in a weight ratio of M) to N) of 60:40 to 20:80, preferably of 55:45 to 25:75.

[0021] In a further preferred embodiment, the polyisocyanate mixture according to the invention, in each case based on the solvent-free solid resin, has color numbers of less than 100 APHA, preferably of less than 80 APHA, particularly preferably of less than 60 APHA, and / or an NCO content of 12.0 to 25.7% by weight, preferably 12.0 to 25.0% by weight, particularly preferably 13.0 to 24.5% by weight, and / or a residual monomer content measured by gas chromatography with an internal standard according to DIN EN ISO 10283:2007-11 of less than 0.14% by weight, preferably less than 0.12% by weight and particularly preferably less than 0.10% by weight.

[0022] In a further preferred embodiment, the polyisocyanate mixture according to the invention has a shear strength according to DIN EN ISO 3219:1994-10 at a shear rate of 250 s -1 measured viscosity at 23°C of less than 6000 mPas, preferably less than 5000 mPas and particularly preferably less than 4000 mPas.

[0023] The weight-average molecular weight of the polyisocyanate mixture according to the invention as well as of the individual polyisocyanates M) and N) used for the mixture is determined in the context of the present invention by means of gel permeation chromatography according to DIN EN ISO 13885-1:2021-11 using polystyrene as standard.

[0024] The at least one polyisocyanate M) is mixed with the at least one polyisocyanate N) such that the polyisocyanate mixture according to the invention is obtained and the polyisocyanates M) and N) are present in the above-mentioned weight ratio to one another. By suitable choice of mixing ratios within the stated limits, properties such as viscosity, NCO content and functionality of the process products according to the invention can be specifically adjusted. Mixing is carried out by any desired method and in any desired sequence, at a temperature of 0 to 60°C, preferably 10 to 50°C, particularly preferably 20 to 40°C, optionally under an inert gas atmosphere, preferably with exclusion of moisture.

[0025] The process according to the invention can be carried out solvent-free. However, suitable solvents that are inert toward the reactive groups of the starting polyisocyanates M) and N) can also be used if desired. Suitable solvents for this purpose include those produced using fossil raw materials or from renewable raw materials, in particular the conventional paint solvents known per se, such as, for example,Ethyl acetate, butyl acetate, ethylene glycol monomethyl or ethyl ether acetate, 1-methoxypropyl-2-acetate, 3-methoxy-n-butyl acetate, ethyl(-)-L-lactate, acetone, 2-butanone, 4-methyl-2-pentanone, cyclohexanone, dihydrolevoglucosenone, toluene, xylene, chlorobenzene, white spirit, higher substituted aromatics, such as those sold under the names Solventnaphtha, Solvesso®, Isopar®, Nappar®, Varsol® (ExxonMobil Chemical Central Europe, Cologne, DE) and Shellsol® (Shell Deutschland Oil GmbH, Hamburg, DE), but also solvents such as dimethylfuran, 2-methyltetrahydrofuran, dimethylisosorbide (DMI), γ-valerolactone, propylene glycol diacetate, diethylene glycol dimethyl ether, Dipropylene glycol dimethyl ether, diethylene glycol ethyl and butyl ether acetate, N-methylpyrrolidone and N-methylcaprolactam, or any mixtures of such solvents.

[0026] In a preferred embodiment of the process according to the invention, 30 to 50 parts by weight of the polyisocyanate M) and 50 to 70 parts by weight of the polyisocyanate N) are mixed. When one or more solvents are used, these can be present either in the at least one polyisocyanate M) and / or in the at least one polyisocyanate N), preferably in the at least one polyisocyanate N) before mixing begins. However, in the process according to the invention, they can also be added after completion or at any time during the actual mixing process.

[0027] If at all, solvents are used in the process according to the invention in an amount of up to 50 wt.%, preferably up to 40 wt.%, particularly preferably up to 30 wt.%, based on the sum of polyisocyanate M), polyisocyanate N) and solvent.

[0028] The polyisocyanates M) and N) are further described below and preferred embodiments are mentioned.

[0029] Polyisocyanate M)

[0030] Suitable polyisocyanates M) for the process according to the invention are polyisocyanates based on HDI containing at least allophanate and / or at least isocyanurate structures, which have a viscosity measured according to DIN EN ISO 3219:1994-10 at 23°C of 100 to 1600 mPas.

[0031] Such polyisocyanates are known. Their preparation is described, for example, in Laas et al., J. Prakt. Chem. 336, 1994, 185-200, as well as in EP-A 0 330 966, EP-A 0 339 396, EP-A 0 377 177, EP-A 0 798 299, EP-A 0 000 016, EP-A 0 000 194, EP-A 0 303 150, EP-A 0 496 208, EP-A 0 524 500, EP-A 0 524 501, EP-A 0 682 012, EP-A 1 445 271, EP-A 1 939 232 and EP-A 2 358 778 described by way of example.

[0032] In addition to allophanate and / or isocyanurate structures, the polyisocyanates M) may optionally also contain, in minor amounts, structures of other isocyanate derivatives, such as uretdione, iminooxadiazinedione, urethane, biuret and / or oxadiazinetrione groups.

[0033] The contents (mol-%) of the allophanate and / or isocyanurate structures and optionally uretdione, iminooxadiazinedione, urethane, biuret and / or oxadiazinetrione structures present in the polyisocyanates M) were determined from the integrals of proton-decoupled 13 C-NMR spectra (recorded on a Bruker DPX-400) were calculated. For HDI polyisocyanates dissolved in CDCh, the individual structural elements exhibit the following chemical shifts (in ppm): allophanate: 155.7 and 153.8; isocyanurate: 148.4; uretdione: 157.1; iminooxadiazinedione: 147.8, 144.3, and 135.3; urethane: 156.3; biuret: 155.5; oxadiazinetrione: 147.8 and 143.9.

[0034] The polyisocyanates M) having allophanate and / or isocyanurate structures have contents of monomeric HDI, measured by gas chromatography according to DIN EN ISO 10283:2007-11 with internal standard, of less than 0.14 wt.%, preferably less than 0.12 wt.% and particularly preferably less than 0.10 wt.%, based on the total weight of the polyisocyanate.

[0035] The polyisocyanates M) are preferably HDI polyisocyanates with allophanate and isocyanurate structures, which particularly preferably have a viscosity of 200 to 1,500 mPas, preferably of 300 to 1,400 mPas, at 23°C, and an isocyanate group content of 16 to 24.5% by weight, preferably of 19 to 24% by weight.

[0036] In these preferred polyisocyanates M) containing allophanate and isocyanurate structures, the proportion of allophanate structures is generally from 20 mol% to 70 mol%, preferably from 30 mol% to 65 mol% and particularly preferably from 40 mol% to 60 mol%, and the proportion of isocyanurate structures is generally from 30 mol% to 80 mol%, preferably from 35 mol% to 70 mol% and particularly preferably from 40 mol% to 60 mol%, in each case determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the HDI polyisocyanate M).

[0037] Polyisocyanate N)

[0038] Suitable polyisocyanates N) for the process according to the invention are any oligomeric polyisocyanates obtainable by modifying 1,5-diisocyanatopentane (pentamethylene diisocyanate, PDI) with uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetrione structure or any mixtures of such PDI polyisocyanates. These polyisocyanates N) are prepared by conventional isocyanate oligomerization methods, as described, for example, in J. Prakt. Chem. 336 (1994) 185-200 and EP-A 0 798 299, by reacting some of the isocyanate groups of the PDI to form polyisocyanate molecules consisting of at least two diisocyanate molecules, followed, as a rule, by distillative or extractive removal of the unreacted monomeric PDI.Concrete examples of such oligomeric PDI polyisocyanates can be found, for example, in EP-A 2 418 198, EP-A 2 684 867, JP 2010-121011, JP 2010-254764, JP 2010-265364, JP 2011-201863, JP 2012-152202, JP 2013-060542.

[0039] The PDI used to produce the polyisocyanates N) is obtainable in various ways, for example by phosgenation in the liquid or gas phase or by a phosgene-free route, such as by thermal urethane cleavage, starting from 1,5-diaminopentane, preferably obtained biotechnologically by decarboxylation of the naturally occurring amino acid lysine. In a preferred embodiment, the PDI polyisocyanate N) is a polyisocyanate obtainable by modifying pentamethylene diisocyanate and having a uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione, and / or oxadiazinetrione structure, preferably having an isocyanurate and / or allophanate structure.

[0040] If necessary, other diisocyanates and triisocyanates other than PDI can also be used in minor amounts when modifying PDI to polyisocyanates N). Suitable diisocyanates and triisocyanates for this purpose are any diisocyanates and triisocyanates obtainable in various ways, for example by phosgenation of the corresponding diamines or triamines, which can be produced using fossil raw materials or renewable raw materials, optionally with a mass balance, in the liquid or gas phase or by a phosgene-free route, such as by thermal urethane cleavage, preferably those in the molecular weight range 140 to 400 with aliphatically, cycloaliphatically, araliphatically and / or aromatically bound isocyanate groups, such as 1,4-diisocyanatobutane.

[0041] 1 .6-Diisocyanatohexan (HDI), 2-Methyl-1 ,5-diisocyanatopentan, 1 ,5-Diisocyanato-2,2- dimethylpentan, 2,2,4- bzw. 2,4,4-Trimethyl-1 ,6-diisocyanatohexan, 1 ,8-Diisocyanatooctan, 1 ,9- Diisocyanatononan 1 ,10-Diisocyanatodecan, 1 ,3- und 1 ,4-Diisocyanatocyclohexan, 1 ,3- und 1 ,4-Bis- (isocyanatomethyl)-cyclohexan, 1-lsocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexan (Isophorondiisocyanat, IPDI), 2,4’- und 4,4'-Diiso-cyanatodicyclohexylmethan (H12-MDI), 4,4'- Diisocyanato-3,3'-dimethyldicyclohexylmethan, 4,4'-Diisocyanato-3,3',5,5'- tetramethyldicyclo-'hexylmethan, 4,4'-Diisocyanato-1 ,1 '-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-menthan, 1 ,3-Diisocyanatoadamantan, 1 ,3-Dimethyl-5,7-diisocyanatoadamantan, 1- lsocyanato-1-methyl-4(3)isocyanato-methylcyclohexan, Bis-(isocyanatomethyl)-norbornan (NBDI), 4-lsocyanatomethyl-1 ,8-octandiisocyanat (Triisocyanatononan;TIN), 1,3- and 1,4-bis(isocyanatomethyl)benzene (xylylene diisocyanate, XDI), 1,3- and 1,4-bis-(2-isocyanatoprop-2-yl)-benzene (TMXDI), 1,3-bis(isocyanatomethyl)-4-methylbenzene, 1,3-bis(isocyanatomethyl)-4-ethylbenzene, 1,3-bis(isocyanatomethyl)-5-methylbenzene, 1,3-bis(isocyanatomethyl)-4,5-dimethylbenzene, 1,4-bis(isocyanatomethyl)-2,5-dimethylbenzene, 1,4-bis(isocyanatomethyl)-2,3,5,6-tetramethylbenzene, 1,3-bis(isocyanatomethyl)-5-tert.-butylbenzene, 1 ,3-Bis(isocyanatomethyl)-4-chlorobenzene, 1,3-Bis(isocyanatomethyl)-4,5-dichlorobenzene, 1,3-Bis(isocyanatomethyl)-2, 4,5,6-tetrachlorobenzene, 1,4-Bis(isocyanatomethyl)-2,3,5,6-tetrachlorobenzene, 1 ,4-Bis(isocyanatomethyl)-;

[0042] 2,3,5,6-tetrabromobenzene, 1,4-bis(2-isocyanatoethyl)benzene and 1,4-

[0043] Bis(isocyanatomethyl)naphthalene, 1,2-, 1,3- and 1,4-diisocyanatobenzene (phenylene diisocyanate), 2,4- and 2,6-diisocyanatotoluene (TDI), 2,3,5,6-tetramethyl-1,4-diisocyanatobenzene, the isomeric diethylphenylene diisocyanates, diisopropylphenylene diisocyanates, diisododecylphenylene diisocyanates and biphenyl diisocyanates, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, 2,2'-, 2,4'- and 4,4'-diisocyanatodiphenylmethane (MDI), 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diisocyanatodiphenylethane, 1,5-diisocyanatonaphthalene (naphthylene diisocyanate, NDI), diphenyl ether diisocyanate, Ethylene glycol diphenyl ether diisocyanate,

[0044] Diethylene glycol diphenyl ether diisocyanate, 1,3-propylene glycol diphenyl ether diisocyanate,

[0045] Benzophenone diisocyanate, triisocyanatobenzene, 2,4,6-triisocyanatotoluene,

[0046] Trimethylbenzene triisocyanate, diphenylmethane-2,4,4'-triisocyanate, 3-methyldiphenylmethane-4,6,4'-triisocyanate, the isomeric naphthalene triisocyanates and methylnaphthalene diisocyanates, triphenylmethane triisocyanate, 2,4-diisocyanato-1-[(5-isocyanato-2-methylphenyl)methyl]benzene or mixtures of at least two such diisocyanates and triisocyanates.

[0047] In addition, monoisocyanates, in particular those in the molecular weight range 99 to 300, such as n-butyl isocyanate, n-amyl isocyanate, n-hexyl isocyanate, n-heptyl isocyanate, n-octyl isocyanate, undecyl isocyanate, dodecyl isocyanate, tetradecyl isocyanate, cetyl isocyanate, stearyl isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, 3- or 4-methylcyclohexyl isocyanate, benzyl isocyanate, phenyl isocyanate or naphthyl isocyanate, can be used in minor amounts in the modification of the PDI to polyisocyanates N).

[0048] If at all, diisocyanates, triisocyanates and / or monoisocyanates other than PDI are used in the modification of PDI to polyisocyanates N) in amounts of up to 30% by weight, preferably up to 20% by weight, particularly preferably up to 10% by weight, based on the total amount of PDI, mono-, di- and triisocyanates.

[0049] The polyisocyanates N) for the process according to the invention preferably have an average isocyanate functionality of 1.8 to 8.0, preferably of 2.0 to 7.0 and particularly preferably of 2.3 to 6.0 and / or a content of isocyanate groups of 6.0 to 26.0 wt.%, preferably 8.0 to 25.0 wt.% and particularly preferably of 10.0 to 24.0 wt.%.

[0050] Particularly preferred polyisocyanate components N) are PDI polyisocyanates containing at least isocyanurate structures and having an average NCO functionality of 2.3 to 5.0 and / or a content of isocyanate groups of 11.0 to 26.0 wt.%.

[0051] Very particularly preferred polyisocyanates N) are polyisocyanates containing isocyanurate structures which have been prepared using PDI as the sole diisocyanate and have an average NCO functionality of 2.3 to 5.0, preferably 2.5 to 4.5, a content of isocyanate groups of 11.0 to 26.0% by weight, preferably 13.0 to 25.0% by weight and a content of monomeric PDI, measured by gas chromatography according to DIN EN ISO 10283:2007-11 with internal standard, of less than 0.14% by weight, preferably less than 0.12% by weight and particularly preferably less than 0.10% by weight, based on the total weight of the polyisocyanate.

[0052] In a further preferred embodiment, the PDI polyisocyanate N) has a viscosity according to DIN EN ISO 3219:1994-10 at 23 °C of 2000 to 36000 mPas, preferably of 4000 to 24000 mPas and particularly preferably of 6000 to 12000 mPas.

[0053] Polyisocyanate chemical and other objects of the invention:

[0054] The polyisocyanate mixtures according to the invention are completely stable to crystallization and remain completely clear and free of turbidity even at 5°C and after four weeks of storage.

[0055] The polyisocyanate mixtures according to the invention represent valuable starting materials for the production of polyurethane plastics by the isocyanate polyaddition process. Therefore, a further subject of the invention is the use of the polyisocyanate mixture according to the invention or of the polyisocyanate mixture obtainable or produced, preferably directly produced, by the process according to the invention as a starting component in the production of polyurethane plastics, preferably for producing a coating on a substrate, wherein the substrate is preferably an optionally pretreated body, in particular of a vehicle, or parts thereof.

[0056] The polyisocyanate mixtures according to the invention are outstandingly suitable as curing agents for plastics. Therefore, a composition comprising either at least one polyisocyanate mixture according to the invention and at least one binder reactive toward isocyanate groups, or comprising at least one polyisocyanate mixture according to the invention, obtainable or prepared by the process according to the invention, and at least one binder reactive toward isocyanate groups, is a further subject of the present invention.

[0057] In a preferred embodiment, the composition according to the invention contains the at least one binder reactive toward isocyanate groups in a component 1) and the at least one polyisocyanate mixture according to the invention in a component 2) or the at least one polyisocyanate mixture obtainable or prepared by the process according to the invention in a component 2). Such a composition is also referred to below as a two-component system.

[0058] Here or alternatively, 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 polyester polyol, polyacrylate polyol or any mixtures of the aforementioned.

[0059] It is particularly preferred in the composition according to the invention 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.

[0060] In a further preferred embodiment, the composition according to the invention is a coating composition which optionally contains one or more auxiliaries and additives.

[0061] In a preferred embodiment, the inventive composition of components 1) and 2) is referred to below as a two-component system or as a coating composition or as a coating agent or as a two-component polyurethane varnish, in which the usual polyether polyols, polyester polyols, polycarbonate polyols and / or polyacrylate polyols are present as the hydroxy-functional component as reactants for the polyisocyanates. Preferred hydroxy-functional components are polyacrylate polyols, i.e., polymers or copolymers of (meth)acrylic acid alkyl esters, optionally with styrene or other copolymerizable olefinically unsaturated monomers.

[0062] Although the polyisocyanate mixtures according to the invention can be used solvent-free due to their low viscosity, they can also be diluted without clouding with conventional solvents, for example the aforementioned isocyanate-inert solvents that may optionally be used in the process according to the invention. In general, the coating compositions formulated with the polyisocyanate mixtures according to the invention, to which the auxiliaries and additives customary in the coatings sector, such as flow control agents, color pigments, fillers, or matting agents, may optionally be incorporated, possess good coating properties even when dried at room temperature. However, the compositions according to the invention can of course also be dried under forced conditions at elevated temperatures or by baking at temperatures up to 260°C.

[0063] 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.

[0064] The use of light stabilizers, in particular UV absorbers such as substituted benzotriazoles, S-phenyltriazines or oxalanilides as well as sterically hindered amines, in particular with 2,2,6,6-tetramethylpiperidyl structures - referred to as HALS - is described as an example in A. Valet, Lichtschutzmittel für Lacke, Vincentz Verlag, Hanover, 1996.

[0065] Stabilizers such as radical scavengers and other polymerization inhibitors such as sterically hindered phenols stabilize coating 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 2).

[0066] The composition according to the invention may further contain pigments, dyes and / or fillers. The pigments used for this purpose, including metallic or other effect pigments, dyes and / or fillers, are known to the person skilled in the art.

[0067] 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.

[0068] If fillers, matting agents or pigments are contained in the composition according to the invention, the addition of anti-settling agents may be useful to prevent separation of the components during storage.

[0069] 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 controlling the properties of the composition during application and during the flow phase on the substrate and are known, for example, from patents 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 layered silicates such as aluminum-magnesium silicates, sodium-magnesium and sodium-magnesium-fluoro-lithium layered 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.

[0070] The composition according to the invention can be used solvent-free, but preferably contains at least one solvent, e.g. in component 1) and / or component 2).

[0071] Suitable solvents should be used in a manner known to those skilled in the art, tailored to the composition used and the application method. Solvents should dissolve the components used, promote their mixing, and avoid incompatibilities. Furthermore, they should leave the coating during application and curing in a manner tailored to the ongoing crosslinking reaction, 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, e.g., from Exxon-Chemie; and mixtures of the aforementioned solvents.

[0072] To control the curing rate, suitable catalysts can be used in the formulation of the coating agents, for example the catalysts commonly used in isocyanate chemistry, such as tertiary amines such as triethylamine, pyridine, methylpyridine, benzyldimethylamine, N,N-endoethylenepiperazine, N-methylpiperidine, pentamethyldiethylenetriamine, N,N-dimethylaminocyclohexane, N,N'-dimethylpiperazine or metal salts such as iron(III) chloride, zinc chloride, zinc 2-ethylcaproate, tin(II) octanoate, tin(II) ethylcaproate, dibutyltin(IV) dilaurate, bismuth(III) 2-ethylhexanoate, bismuth(III) octoate or molybdenum glycolate.

[0073] The polyisocyanate mixtures according to the invention are also suitable as crosslinking components for binders or binder components containing isocyanate-reactive groups, particularly alcoholic hydroxyl groups, dissolved or dispersed in water in the production of aqueous two-component polyurethane systems. Due to their low viscosity, they can be used either as such, i.e., in hydrophobic form, or in hydrophilically modified form by known processes, e.g., according to EP-B 0 540 985, EP-B 0 959 087, or EP-B 1 287 052.

[0074] The polyisocyanate mixtures according to the invention can also be combined with polyamines, such as the polyaspartic acid derivatives known from EP-B 0 403 921, obtainable by reacting diamines with fumaric acid or maleic acid esters, or with polyamines whose amino groups are present in blocked form, such as polyketimines, polyaldimines, or oxazolanes. Under the influence of moisture, these blocked amino groups form free amino groups and, in the case of oxazolanes, also free hydroxyl groups, which react with the isocyanate groups of the polyisocyanate mixtures according to the invention to form crosslinking compounds. Furthermore, the polyisocyanate mixtures according to the invention can also be combined with compounds containing at least one thiol group.

[0075] These are, for example, the polythiols known from EP-A 3 872 108, such as simple alkanethiols, polythiols containing thioether groups, polyetherthiols, polyesterthiols, aromatic thio compounds and / or mercapto alcohols.

[0076] According to a preferred embodiment, the isocyanate groups of the polyisocyanate mixtures according to the invention can be partially or completely reacted with at least one blocking agent.

[0077] These blocking agents are, in particular, blocking agents known per se from polyurethane chemistry, such as, for example, malonic acid diethyl ester, acetoacetic ester, activated cyclic ketones, such as, for example, cyclopentanone-2-carboxymethyl ester and -carboxyethyl ester, acetone oxime, butanone oxime, e-caprolactam, 3,5-dimethylpyrazole, 1,2,4-triazole, dimethyl-1,2,4-triazole, imidazole, diisopropylamine, benzyl-tert-butylamine or any mixtures of these blocking agents.

[0078] In blocked form, the polyisocyanate mixtures according to the invention can also be used in combination with the above-mentioned paint binders or paint binder components in the sense of one-component PUR stoving systems.

[0079] In all coating combinations, the polyisocyanate mixtures according to the invention and the reactant are present in amounts such that 0.5 to 3, preferably 0.6 to 2.0, particularly preferably 0.8 to 1.6, optionally blocked, isocyanate-reactive groups are present for each optionally blocked isocyanate group. If desired, the allophanate polyisocyanates according to the invention can also be admixed in minor amounts to non-functional coating binders to achieve very specific properties, for example, as an additive to improve adhesion.

[0080] Any substrates can be considered as substrates for the coatings formulated with the aid of the polyisocyanate mixtures according to the invention, such as metal, wood, glass, stone, ceramic materials, concrete, hard and flexible plastics, textiles, leather and paper, which can optionally also be provided with conventional primers before coating.

[0081] The invention further provides a process for producing a coating on a substrate, comprising the following steps: a) providing an optionally pretreated substrate; b) applying at least one composition according to the invention; and c) curing the composition, optionally with the addition of heat.

[0082] The invention thus further provides coating compositions comprising the polyisocyanate mixtures according to the invention, and 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 of the materials selected from metal, plastic or mixtures thereof. Alternatively or additionally, the coated substrate is at least partially coated with a polyurethane, polyurea and / or polythiourethane according to the invention and / or at least one polyisocyanate mixture according to the invention and / or at least one coating composition according to the invention. The polyisocyanate mixtures or compositions according to the invention can also be used very well in direct coating applications and result in corresponding directly coated substrates.

[0083] The coating compositions according to the invention can be present, for example, as a two-component system comprising a crosslinker component containing at least one polyisocyanate mixture according to the invention and a binder component containing at least one paint binder or a paint binder component with groups reactive toward isocyanate groups, or as a one-component system containing at least one polyisocyanate mixture according to the invention in blocked form. Such systems are also the subject of the present invention.

[0084] In addition to the preferred use as crosslinker components for solvent-free, solvent-based or aqueous 2K-PUR coatings, the polyisocyanate mixtures according to the invention are outstandingly suitable as crosslinkers for solvent-free or solvent-based adhesive binders or aqueous dispersion adhesives, or also as build-up components for the production of lightfast compact or foamed polyurethane moldings.

[0085] Therefore, a further subject matter of the invention are polyurethanes, polyurea and / or polythiourethanes, obtainable or prepared by reacting at least one polyisocyanate mixture according to the invention with at least one hydroxy-, amino- and / or thiofunctional component.

[0086] The features identified as preferred for the process according to the invention or the polyisocyanate mixture according to the invention are also preferred for the further subject matters of the invention.

[0087] The following examples serve to illustrate the present invention, but should in no way be understood as a limitation of the scope of protection.

[0088] Examples:

[0089] Unless otherwise stated, all percentages are based on weight.

[0090] The NCO content was determined titrimetrically according to DIN EN ISO 11909:2007-05.

[0091] The residual monomer contents were measured according to DIN EN ISO 10283:2007-11 using gas chromatography with an internal standard.

[0092] 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.

[0093] The platinum-cobalt color number was measured spectrophotometrically according to DIN EN ISO 6271-2:2005-03 using a LICO 400 spectrophotometer from Lange, Germany.

[0094] The contents (mol-%) of the allophanate and / or isocyanurate structures and optionally uretdione, iminooxadiazinedione, urethane, biuret and / or oxadiazinetrione structures present in the polyisocyanates M) were determined from the integrals of proton-decoupled 13 C-NMR spectra (recorded on a Bruker DPX-400) were calculated. For HDI polyisocyanates dissolved in CDCh, the individual structural elements exhibit the following chemical shifts (in ppm): allophanate: 155.7 and 153.8; isocyanurate: 148.4; uretdione: 157.1; iminooxadiazinedione: 147.8, 144.3, and 135.3; urethane: 156.3; biuret: 155.5; oxadiazinetrione: 147.8 and 143.9.

[0095] The drying properties of the coating systems were determined according to DIN 53 150:2002-09.

[0096] The gloss of the resulting coatings was measured reflectometrically according to DIN EN ISO 2813:1999-06 at a 20° angle.

[0097] The determination of pendulum damping according to König was carried out according to DIN EN ISO 1522:2007-04 on glass plates.

[0098] 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 was placed over the opening to create a solvent-saturated atmosphere inside the test tubes. The test tubes were then placed with the cotton ball on the surface of the coatings applied to glass 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 carried out analogously using premium gasoline E10.

[0099] The wet scratch resistance of the coatings was tested using a laboratory washing system according to DIN EN ISO 20566:2010-08. The gloss loss is expressed in Gloss Units (GU) after scratching (10 cycles). The lower the gloss loss in GU, the more resistant the coating is to wet scratching. Polyisocyanate N1)

[0100] PDI polyisocyanate containing isocyanurate groups, prepared by catalytic trimerization of PDI according to the process described in WO 2016 / 146579 for polyisocyanate component A2). The reaction was deactivated at an NCO content of the crude mixture of 36.7% by adding an equimolar amount of dibutyl phosphate, based on the amount of catalyst used, and stirring for 30 minutes at 80°C. Unreacted PDI was then removed by thin-film distillation at a temperature of 140°C and a pressure of 0.5 mbar.

[0101] NCO content: 21.8% monomeric PDI: 0.09%

[0102] Viscosity (23 °C): 9850 mPas

[0103] Color number (Hazen): 34

[0104] Polyisocyanate N2)

[0105] 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.

[0106] NCO content: 21.7%

[0107] Monomeric HDI: 0.1%

[0108] Viscosity (23°C): 3080 mPas

[0109] Color number (Hazen): 18

[0110] Polyisocyanate N3)

[0111] HDI polyisocyanate containing isocyanurate groups, prepared by catalytic trimerization of HDI based on Example 11 of EP-A 330 966, with the modification 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 separated by thin-film distillation at a temperature of 130°C and a pressure of 0.2 mbar. The product had the following characteristics and composition:

[0112] NCO content: 22.9% monomeric HDI: 0.08%

[0113] Viscosity (23°C): 1210 mPas

[0114] Color number (Hazen): 10

[0115] Polyisocyanate M1)

[0116] HDI polyisocyanate containing allophanate and isocyanurate groups, prepared by catalytic trimerization of HDI in the presence of n-butanol according to Example 4 of EP-A 496 208, except that the reaction was stopped at an NCO content of the crude mixture of 36.2% 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.

[0117] The product had the following characteristics and composition:

[0118] NCO content: 20.0% monomeric HDI: 0.06%

[0119] Viscosity (23°C): 510 mPas

[0120] Color number (Hazen): 12

[0121] Composition: Allophanate: 51.0 mol-%

[0122] Isocyanurate: 47.3 mol%

[0123] Uretdione: 1.7 mol% 1)

[0124] 30 parts by weight of polyisocyanate M1) were homogeneously mixed with 70 parts by weight of polyisocyanate N1) at 50°C by stirring. After cooling to room temperature, a polyisocyanate mixture 1 according to the invention was obtained with the following characteristics:

[0125] NCO content: 21.3% monomeric HD I / PDI: 0.02 / 0.06%

[0126] Viscosity (23°C): 3420 mPas

[0127] Color number (Hazen): 17

[0128] Example 2 (Preparation of polyisocyanate mixture 2)

[0129] 50 parts by weight of polyisocyanate M1) were mixed homogeneously with 50 parts by weight of polyisocyanate N1) at 50°C by stirring. After cooling to room temperature, a polyisocyanate mixture 2 according to the invention was obtained with the following characteristics:

[0130] NCO content: 20.9% monomeric HD I / PDI: 0.03 / 0.05%

[0131] Viscosity (23°C): 1950 mPas

[0132] Color number (Hazen): 15 (Coating composition and coating according to the invention and

[0133] Comparison)

[0134] 166.9 parts by weight of the commercially available polyacrylate polyol Uralac CY240 EF-75 (Covestro AG, Leverkusen, Germany) with a solids content of 74 wt.% and an OH content (based on the solids) of 4.0%, corresponding to an equivalent weight of 425 g / eq OH, were mixed with 2.9 parts by weight of a 10% solution of a commercially available leveling additive (BYK 331; BYK-Chemie GmbH, Wesel, Germany) in butyl acetate, 5.8 parts by weight of a 1% solution of dibutyltin dilaurate (DBTL) in butyl acetate as catalyst, 1.9 parts by weight of a 50% solution of a commercially available light stabilizer (Tinuvin 123; BASF SE, Ludwigshafen, Germany), Tinuvin 384-2 (BASF SE, Ludwigshafen, DE) (used as a 50% solution in butyl acetate) and the commercially available surface additive BYK-358 N (BYK-Chemie GmbH, Wesel, DE; used as supplied) were mixed homogeneously by intensive stirring at room temperature. Subsequently, the mixture was homogenized by adding an equal weight of-parts of butyl acetate and xylene and further intensive stirring, a non-volatile content of 68 wt.% was achieved.

[0135] The polyisocyanate mixtures according to the invention or comparative polyisocyanates (component B) were stirred into this base paint component (component A) and the solids content of the finished coating compositions was adjusted with butyl acetate / xylene (1 : 1) to a flow time of approx. 20 s in an ISO cup with a 4 mm nozzle.

[0136] Table 1 : Compositions of the individual formulations

[0137] To determine the pendulum damping according to König and to test solvent and gasoline resistance, the coating materials were applied to glass plates using a gravity-feed gun in a wet film thickness of 150 μm. After 10 minutes of flash-off at room temperature, they were cured within 30 minutes at 60°C. All glass plates were stored at room temperature for at least 48 hours prior to testing.

[0138] To determine scratch resistance, the coating materials were applied as clear coats using a gravity-feed gun (dry film thickness approx. 50 μm) to e-coated panels that had previously been coated with a commercially available 1-component OEM hydro-filler (dry film thickness approx. 35 μm) and a black 1-component OEM hydro-basecoat (dry film thickness approx. 15 μm). The clear coats were cured within 30 minutes at 60°C. All panels were stored at room temperature for at least 48 hours prior to testing. Table 2: Results of the application tests

[0139] The comparison of Examples 3 and 4 with Comparative Examples 5 and 6 shows that the use of the polyisocyanate mixtures 1 and 2 according to the invention, which contain high proportions of the bio-based PDI but have significantly lower viscosities than the PDI polyisocyanate N1), as crosslinkers for automotive refinish clearcoats leads to coatings with comparable coating properties to crosslinking with the standard HDI trimers N2) and N3).

Claims

Patent claims 1. Polyisocyanate mixture containing at least one HDI polyisocyanate M) having allophanate and / or isocyanurate structures and having a viscosity at 23°C of 100 to 1600 mPas, determined according to DIN EN ISO 3219:1994-10 at a shear rate of 250 s-1, and at least one PDI polyisocyanate N) in a weight ratio to one another of 80:20 to 20:

80.

2. Polyisocyanate mixture according to claim 1, characterized in that the weight ratio of the HDI polyisocyanate M) and the PDI polyisocyanate N) to one another is 60:40 to 20:80 and preferably 55:45 to 25:

75.

3. Polyisocyanate mixture according to claim 1 or 2, characterized in that it has an NCO content determined according to DIN EN ISO 11909:2007-05 of 12.0 to 25.7 wt.%, preferably 12.0 to 25.0 wt.%, particularly preferably 13.0 to 24.5 wt.%.

4. Polyisocyanate mixture according to one of claims 1 to 3, characterized in that the PDI polyisocyanate N) has a viscosity according to DIN EN ISO 3219:1994-10 at 23 °C of 2000 to 36000 mPas, preferably of 4000 to 24000 mPas and particularly preferably of 6000 to 12000 mPas.

5. Polyisocyanate mixture according to one of claims 1 to 4, characterized in that the PDI polyisocyanate N) is a polyisocyanate obtainable by modification of pentamethylene diisocyanate with uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and / or oxadiazinetrione structure, preferably with isocyanurate and / or allophanate structure.

6. Polyisocyanate mixture according to one of claims 1 to 5, characterized in that the PDI polyisocyanate N) has an average isocyanate functionality of 2.3 to 5.0 and / or a content of isocyanate groups of 11.0 to 26.0 wt.% and / or is a polyisocyanate containing isocyanurate structures which was prepared using pentamethylene diisocyanate as the sole diisocyanate.

7. Polyisocyanate mixture according to one of claims 1 to 6, characterized in that the HDI polyisocyanate M) has allophanate and isocyanurate structures.

8. Polyisocyanate mixture according to one of claims 1 to 7, characterized in that the HDI polyisocyanate M) has an allophanate group content of 20 mol% to 70 mol%, preferably 30 mol% to 65 mol% and particularly preferably 40 mol% to 60 mol%, and an isocyanurate group content of 30 mol% to 80 mol%, preferably 35 mol% to 70 mol% and particularly preferably 40 mol% to 60 mol%, in each case determined by NMR spectroscopic analysis and based on the total amount of isocyanurate groups and allophanate groups of the polyisocyanate mixture M).

9. A process for preparing a polyisocyanate mixture according to any one of claims 1 to 8, characterized in that at least one HDI polyisocyanate M) having allophanate and / or isocyanurate structures and at least one PDI polyisocyanate N) are mixed so that the polyisocyanates M) and N) are present in a weight ratio to one another of 80:20 to 20:80, preferably of 60:40 to 20:80, particularly preferably of 55:45 to 25:

75.

10. Composition comprising either at least one polyisocyanate mixture according to one of claims 1 to 8 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 9 and at least one binder reactive towards isocyanate groups.

11. Composition according to claim 10, characterized in that it contains the at least one binder reactive towards isocyanate groups in a component 1) and the at least one polyisocyanate mixture according to one of claims 1 to 8 in a component 2) or the at least one polyisocyanate mixture obtainable or produced according to a process according to claim 9, in a component 2) 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. Composition according to claim 10 or 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 one of claims 1 to 8 or of a composition according to 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. Polyurethane, polyurea and / or polythiourethane, obtainable or prepared by reacting at least one polyisocyanate mixture according to one of claims 1 to 8 with at least one hydroxy-, amino- and / or thiofunctional component.

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

16. Coated substrate obtainable or produced by a process according to claim 15, 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.

Images