MXPA97000787A - Polyisocianatos of low surface energy and its use in compositions of coating of one or two components - Google Patents

Abstract

The present invention relates to a mixture of polyisocyanates which i) has an NCO content of 5 to 35% by weight and is prepared from an organic diisocyanate, ii) contains up to 25% by weight of isocyanurate groups (calculated as N3, C3, O3, MW 126), iii) contains allophanate groups in an amount such that there are more equivalents of allophanate groups than of urethane and urea groups and such that the mixture of polyisocyanates remains stable and homogeneous in storage for 3 months to 25 minutes. §C and iv) contains siloxane groups (calculated as SiO, PM 44) in an amount of 0.002 to 50% by weight, where the above percentages are based on the solids content of the polyisocyanate mixture, excluding any unreacted organic diisocyanate , and where the siloxane groups are incorporated by reaction of an isocyanate group with a compound containing two or more isocyanate-reactive groups directly attached to carbon atoms and one or more siloxa groups

Description

POLYISOCIANATES OF LOW SURFACE ENERGY AND ITS USE IN COATING COMPOSITIONS OF ONE OR TWO COMPONENTS BACKGROUND OF THE INVENTION Field of the Invention The present invention is directed to low surface energy polyisocyanates containing allophanate groups, siloxane groups and, optionally, isocyanurate groups, to a process for their preparation by allophanatization of the isocyanate groups of organic diisocyanates in the presence of isocyanate-reactive compounds containing siloxane groups and their use in one- and two-component coating compositions. Description of the Prior Art Polyurethane coating compositions containing a polyisocyanate component, either in blocked or unblocked form, and an isocyanate-reactive component, generally a high molecular weight polyol, are well known. Although the coatings prepared from these compositions possess many valuable properties, one property, in particular, that needs to be improved is the surface quality. It can be difficult to formulate coating compositions to obtain a coating having a smooth surface, as opposed to one containing surface defects such as craters, etc. It is believed that these difficulties are related to the high surface tension of the two component coating compositions. Another problem caused by high surface tension is the difficulty in cleaning the coatings. Regardless of its potential application area, there is a high probability that the coatings are subject to stains, graffiti, etc. Accordingly, it is an object of the present invention to provide coating compositions that have a lower surface tension and, therefore, are suitable for coating production with lower surface energies and better surfaces. It is a further object of the present invention to provide coating co-locations having a better cleaning ability. It is a final object of the present invention to provide coating compositions that meet these requirements without substantially affecting a. the other valuable properties of the known polyurethane coatings, in particular their clarity. Surprisingly, these objects can be achieved by formulating coating compositions with the polyisocyanates according to the present invention, which contain allophanate groups, siloxane groups and, optionally, isocyanurate groups, which are described below. • US Patent No. 4,590,224 is directed to the production of fully reacted polymers, primarily in the form of molded articles or foams, which are prepared by reacting a polyisocyanate with a polysiloxane polyal in the presence of a trimerization catalyst. In addition to the oligomerization of the polyisocyanate to form isocyanurate groups, a portion of the isocyanate groups react with the polyally to form urethane and urea groups depending on the type of polyals. This patent does not suggest the incorporation of allophanate groups to the polyisocyanate component and certainly does not recognize the importance of the incorporation of allophanate groups to maintain the clarity of the polyurethane coatings. The incorporation of fluorine into polyisocyanates containing allophanate groups and isocyanurate groups or polyisocyanates containing allophanate groups to reduce the surface tension of the polyisocyanates and the surface energy of the resultant polyurethane coatings is not disclosed in the co-pending applications, US Pat. Serial Nos. 08 / 306,553 and 08 / 359,777, respectively. Similarly, the incorporation of siloxane groups through allophanate groups using monoalcohols to reduce the surface tension of the polyisocyanates and the surface energy of the resulting polyurethane coatings is described in the co-pending application, USA Serial No. 08 / 536,556. COMPENDIUM OF THE INVENTION The present invention is directed to a mixture of polyisocyanates that i) has an NCO content of 5 to 35% by weight and is prepared from an organic diisocyanate, ii) contains up to 25% by weight of groups isocyanurate (calculated as N3, C3.03, MW 126), iii) contains allophanate groups in an amount such that there are more equivalents of allophanate groups than of urethane and urea groups and such that the mixture of polyisocyanates remains stable and homogeneous in storage during 3 months at 25 ° C and iv) contains siloxane groups (calculated as SiO, MW 44) in an amount of 0.002 to 50% by weight, where the above percentages are based on the solids content of the polyisocyanate mixture, excluding any unreacted organic diisocyanate, and where the siloxane groups are incorporated by reaction of an isocyanate group with a compound containing two or more isocyanate-reactive groups directly attached to the carbon atoms; arbono and one or more siloxane groups.

The present invention is also directed to a process for the production of a mixture of polyisocyanates which i) has an NCO content of 5 to 35% by weight and is prepared from an organic diisocyanate, ii) contains up to 25% by weight weight of isocyanurate groups (calculated as N3, C3.03, MW 126), iii) contains allophanate groups in an amount such that there are more equivalents of allophanate groups than of urethane and urea groups and such that the mixture of polyisocyanates remains stable and homogeneous in storage for 3 months at 25 ° C and iv) contains siloxane groups (calculated as SiO, PM 44) in an amount of 0.002 to 5.0% by weight, where the above percentages are based on the solids content of the mixture of polyisocyanates, excluding any unreacted organic diisocyanate, by a) reaction of a portion of the isocyanate groups of an organic diisocyanate with 0.01 to 250 millimoles, per mole of organic diisocyanate, of a since it contains two or more isocyanate-reactive groups directly attached to carbon atoms and one or more siloxane groups and, optionally, a monofunctional or polyfunctional alcohol containing no siloxane to form urethane groups and, optionally, urea, provided that at least one of the isocyanate-reactive compounds contain hydroxy lo groups; b) addition of a allophanatization catalyst and, optionally, a trimerization catalyst before, during or after step a); c) conversion of a sufficient amount of the urethane groups formed in step a) into allophanate groups to satisfy the requirements of iii); d) completion of the allophanatization and trimerization reaction to the desired NCO content by adding a catalyst poison and / or thermally deactivating the catalyst, and e) eventual removal of the unreacted organic diisocyanate. The present invention also relates to the use of the mixture of polyisocyanates, optionally in blocked form, as an isocyanate component in one or two component coating compositions. DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the term "(cyclic) aliphatically bound isocyanate groups" means isocyanate groups attached aliphatically and / or cycloaliphatically. The term "monoalcohol" means a compound containing a hydroxyl group attached to aliphatic, cycloaliphatic, araliphatic or aromatically. The term "polyfunctional alcohol" means a compound that contains two or more aliphatic, cycloaliphatic, araliphatic and / or aromatically bound hydroxyio groups. In a preferred embodiment of the present invention, the polyisocyanate mixtures are prepared from organic diisocyanates represented by the formula R (NCO) 2 wherein R represents an organic group obtained by elimination of the isocyanate groups of an organic diisocyanate having aromatic or, preferably (cyclo) aliphatically bound isocyanate groups and a molecular weight of 140 to 400. Preferred diisocyanates for the process according to the invention are those represented by the above formula, wherein R represents a divalent aliphatic hydrocarbon group of 4 to 18 carbon atoms, a divalent cycloaliphatic hydrocarbon group of 5 to 15 carbon atoms, a divalent aromatic hydrocarbon group of 6 to 15 carbon atoms or a divalent araliphatic hydrocarbon group of 7 to 15 carbon atoms. Examples of organic diisocyanates that are particularly suitable for the process include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (DIH), 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, diisocyanate. of 1, 12-dodecamethylene, 1,3- and 1,4-cyclohexane diisocyanate, l-isocyanato-2-isocyanate-tomethylcyclopentane, l-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane (isophorone diisocyanate or DIIF), 4,4'- and / or 2,4 '-diisocyanatodicyclohexylmethane, 1,3- and 1,4-bis (isocyanatomethyl) cyclohexane, bis (4-isocyanato-3-methylcyclohexyl) methane, xylylene diisocyanate, di, a, a, a ', a'-tetramethyl-1, 3- and / or -1, 4-xylylene, 1-isocyanate-1 -methyl-4 (3) -isocyanatomethylcyclohexane, 2,4- and / or 2,6-hexahydrotoluylene diisocyanate, 2,4- and / or 2,6-toluene d-isocyanate, 2,4- diisocyanate and / or 4, 4 '-diphenylmethane. Mixtures of these diisocyanates can also be used. Preferred diisocyanates are 1,6-hexamethylene diisocyanate, isophorone diisocyanate and bis (4-isocyanatocyclohexyl) methane.; the 1,6-hexamethylene-diisocyanate is especially preferred. It is also possible according to the present invention to use mixtures of the aforementioned diisocyanates with monoisocyanates or polyisocyanates having 3 or more isocyanate groups. Suitable methods for the preparation of polyisocyanates containing allophanate groups are known and are described in US Pat. 3,769,318, 4,160,080 and 4,177,342 and 4,738,991, the descriptions of which are hereby incorporated by reference. The allophanatization reaction can be carried out at a temperature of 50 to 250 ° C, preferably 60 to 150 ° C and, more preferably, 70 to 120 ° C. The reaction can be terminated by reducing the reaction temperature, removing the catalyst, for example by applying a vacuum, or by adding a catalyst poison. After the reaction is completed, unreacted monomeric diisocyanates can be removed, for example, by thin film evaporation. The allophanatization of the starting diisocyanate mixture can be carried out in the absence or in the presence of solvents inert to the isocyanate groups.

Depending on the area of application of the products according to the invention, medium boiling solvents or high boiling solvents can be used. Suitable solvents include esters such as ethyl acetate or butyl acetate, ketones such as acetone or butanone, aromatic compounds such as toluene or xylene, halogenated hydrocarbons such as methylene chloride and trichlorethylene, ethers such as diisopropyl ether and alkanes. such as cyclohexane, petroleum ether or ligroin. Instead of employing just catalysts that promote the formation of allophanate groups, it is also possible according to the present invention to also use catalysts that promote the formation of isocyanurate groups or use catalysts that promote the formation of allophanate groups and isocyanurate groups. Suitable methods and catalysts for the preparation of polyisocyanates containing isocyanurate groups and allophanate groups are known and described in US Pat. 5,124,427, . 208,334, 5,235,018 and 5,444,146, the descriptions of which are hereby incorporated by reference. The trimerization of the starting diisocyanate mixture can be carried out in the absence or in the presence of solvents which are inert to the isocyanate groups, such as those previously described.

According to the present invention, urethane and / or urea groups, preferably urethane groups, are incorporated into the polyisocyanates by the use of compounds containing two or more isocyanate-reactive groups directly attached to the carbon atoms, preferably hydroxyl groups, and one or more siloxane groups, preferably in the form of dimethylsiloxane groups, -Si (CH3) 20-. Examples of these compounds are those corresponding to the formula Y-Ra-X- [Si (R2) 20-] n- [Si (R2) 2-X] m -R1-Y wherein R1 represents a divalent hydrocarbon radical optionally substituted inert , preferably an alkylene radical (such as methylene, ethylene, propylene or butylene) or a polyoxyalkylene group (such as a polyethylene or polyoxypropylene group); R 2 represents hydrogen or a lower alkyl group, phenyl or benzyl optionally inert substituted, preferably ethyl or methyl, more preferably methyl; X represents a bond between a group R1 and an Si atom, for example a covalent bond, -O- or -COO ~; Y is an isocyanate reactive group, preferably a hydroxyl group or a primary or secondary aminb group, more preferably a hydroxyl group; m is 0 or 1, and n is an integer from 1 to 1,000, preferably 2 to 100 and, more preferably, 4 to 15. Inert substituents are those which do not interfere with the reaction of the siloxane compound with the polyisocyanate or allophanate and / or the reaction of the isocyanate groups. Examples include halogen atoms such as fluorine. An example of compounds in which R1 represents an oxyalkylene group are compounds corresponding to the formula Y- (CHR3-CH20-) or- (R4) m- [Si (R2) 20-] n- (CH2-CHR3-0- pC ^ 2-CHR3-Y where R2, Y, m and n are as defined above; R3 is hydrogen or an alkyl group of 1 to 12 carbon atoms, preferably hydrogen or methyl; R 4 represents an optionally inertly substituted divalent hydrocarbon radical, preferably an alkylene radical (such as ethylene, ethylene, propylene or butylene); or is an integer from 1 to 200, preferably 2 to 50 and, more preferably, 4 to 25, and p is an integer from 0 to 200, preferably 2 to 50 and, more preferably, 4 to 25. These siloxane compounds are prepared by reacting the appropriate siloxane with an amount of an alkylene oxide (preferably, ethylene or propylene oxide) sufficient to prepare a compound having the desired content of siloxane. The amino or alkyleneamino groups are introduced by aminating the resulting hydroxyl-terminated compound in a known manner. Other suitable groups containing siloxane can be linear, branched or cyclic and have a molecular weight (number average molecular weight determined by gel permeation chromatography using polystyrene as a standard) of up to 50,000, preferably up to 10,000, more preferably up to 6,000, and more preferably, up to 2,000. they have in general OH numbers of more than 5, preferably more than 25 and, more preferably, more than .35. Compounds of this type are described in "Silicon Compounds", 5th Edition, by Hüls America, Inc. To prepare the polyisocyanate mixtures according to the invention, the minimum ratio of compounds containing siloxane to diisocyanate is approximately 0.01 millimole, preferably about 0.1 millimole and, more preferably, about 1 millimole of siloxane-containing compounds per mole of diisocyanate. The maximum amount of compounds containing siloxane to diisocyanate is about 250 millimoles, preferably about 50 millimoles and, more preferably, about 20 millimoles of siloxane-containing compyesto per mole of diisocyanate. The amount of the siloxane is selected such that the resulting polyisocyanate mixture contains a minimum of 0.005% by weight, preferably 0.01% by weight and, more preferably, 0.1% by weight, of siloxane groups ( MW 44), based on the solids, and a maximum of 50% by weight, preferably 10% by weight, more preferably, 7% by weight and, more preferably, 3% by weight of siloxane groups (MW 44), based on solids. In addition to the previously described compounds containing siloxane groups, other monofunctional or polyfunctional alcohols, preferably monoalcohols, which do not contain siloxane groups, can also be used to adjust the properties of the final products. For example, monoalcohols containing no siloxane groups can be used to reduce the viscosity of the polyisocyanate mixtures. Suitable monoalcohols of this type have been described in US Pat. 5,124,427, 5,208,334, 5,235,018 and 5,444,146, whose descriptions have previously been incorporated as a reference. When the siloxane compounds do not contain sufficient hydroxyl groups to subsequently meet the required contents in allophanate groups, for example when amino-functional siloxanes are used, it is necessary to use these eventual alcohols which do not contain siloxane. These alcohols react with the polyisocyanate component to form urethane groups and subsequently the allophanate groups, which are essential for the present invention. Examples of suitable monoalcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, isobutanol, tert-butanol, n-petanol, 2-hydroxypentane, 3-hydroxypentane, methylbutanol alcohols. isomers, isomeric dimethylpropyl alcohols, neopentyl alcohol, n-hexanol, n-heptanol, n-octanol, n-nonanol, 2-ethylhexanol, trimethylhexanol, cyclohexanol, benzyl alcohol, phenol, cresols, xylene, trimethylphenols, decanol, dodecanol, tetradecanol, hexadecanol, octadecanol, 2,6,6-trimethylnone-nol, 2-t-butylcyclohexanol, 4-cyclohexyl-1-butanol, 2, 4,6-trimethylbenzyl alcohol, branched chain primary alcohols and mixtures thereof ( available from Henkel under the trademark Standamul) and mixtures of linear primary alcohols (available from Shell under the trademark Neodol). Preferred ether-containing monoalcohols include ethoxymethanol, methoxyethanol, ethoxyethanol, isomeric methoxy or ethoxypropanoles, propoxymethane and isomeric ethanols, isomeric methoxybutanols, isomeric butoxymethanols, furfuralcohol and other monoalcohols having a molecular weight of up to 2000 and are prepared from ethylene oxide, propylene oxide and / or butylene oxide. It is also possible according to the present invention to use mixtures of the monoalcohols previously described. When polyisocyanates containing allophanate groups andoptionally, isocyanurate groups according to the invention are prepared from monoalcohols containing ethylene oxide units, the polyisocyanates can be dispersed in water as described in US Pat. 5,200,489, the description of which is hereby incorporated by reference. The process according to the invention can take place batchwise or continuously, for example, as described above. The starting diisocyanate is introduced in the exclusion of moisture and, optionally, with an inert gas, into a suitable stirred vessel or tube and, optionally, mixed with a solvent which is inert to the isocyanate groups, such as toluene, butyl acetate, diisopropyl ether or cyclohexane. The above-described isocyanate-reactive siloxane compounds and optional alcohols can be introduced into the reaction vessel according to various embodiments. They can pre-react with the starting diisocyanate to form urethane groups and, optionally, urea before introducing the diisocyanate into the reaction vessel; they can be mixed with the diisocyanates and introduced into the reaction vessel; they can be added separately to the reaction vessel sooner or later, preferably afterwards, of adding the diisocyanates; or the catalyst can be dissolved in these compounds before introducing the solution into the reaction vessel. At a temperature of about 50 ° C and in the presence of the required catalyst or catalyst solution, the allophanatization reaction begins and is indicated by an exothermic reaction. When catalysts are present for the formation of allophanate groups and isocyanurate groups, it is possible to control the rate of formation of these two groups. As the temperature of the reaction increases, the rate of conversion of the urethane groups to allophanate groups increases faster than the formation of isocyanurate groups. Consequently, by varying the reaction temperature, it is possible to obtain different allophanate group ratios with respect to isocyanurate groups. The progress of the reaction is followed by determining the NCO content by a suitable method such as titration, refractive index or IR analysis. Thus, the reaction can be terminated to the desired degree of allophanatization. The completion of the allophanatization reaction can take place, for example, after the NCO content has fallen by 5 to 80% by weight, preferably 10 to 60% by weight and, more preferably, 20% by weight. 50% by weight, based on the initial content of isocyanate groups of the diisocyanate starting material. In general, when the reaction is terminated at a high NCO content, ie, before the NCO content has been significantly reduced, the resulting mixture of polyisocyanates after removal of the unreacted starting diisocyanate will have a low viscosity. Conversely, if the reaction ends at a low NCO content, ie, after the NCO content has dropped significantly, then the resulting product will have a higher viscosity due to the formation of polyisocyanurates and other higher molecular weight byproducts. of the isocyanurates and allophanates that are initially formed. This is especially true with respect to the known aliphatic diisocyanate starting materials. The cyclic diisocyanates give rise to products or solids of extremely high viscosity after removal of the unreacted monomer irrespective of when the reaction is terminated. The termination of the allophanatization reactions and, optionally, of trimerization, can take place, for example, by the addition of a catalyst poison of the type mentioned by way of example in the literature references mentioned above. For example, when basic catalysts are used, the reaction is terminated by adding an amount, which is at least equivalent to the amount of the catalyst, of an acid chloride such as benzoyl chloride. When heat-labile catalysts are used, for example, certain quaternary ammonium hydroxides, the poisoning of the catalyst by addition of a catalyst poison can be dispensed with, since these catalysts decompose in the course of the reaction. It is also possible the use of suspended catalysts. These catalysts are removed after achieving the desired degree of trimerization by filtering the reaction mixture. The manipulation of the reaction mixture, optionally after a previous separation of the insoluble catalyst constituents, can take place in various ways depending on how the reaction was carried out and the area of application of the isocyanates. Any solvent used during the reaction and any unreacted monomer present in the polyisocyanate product can be separated by distillation in a known manner. The product obtained after the distillation generally contains a total of less than 2% by weight, preferably less than 1% by weight, based on the solids content of the mixture of polyisocyanates, free monomeric diisocyanates (unreacted). The products according to the invention vary from low viscosity liquids having a viscosity of 200 mPa.s to high viscosity liquids to solids. Low viscosity products are generally obtained from aliphatic diisocyanate starting materials. such as 1,6-hexamethylene diisocyanate and have a viscosity of less than 500 * 0, preferably less than 2000 and, more preferably, less than 1300 mPa.s. The high viscosity products can also be obtained from these diisocyanates, but the reaction is terminated at a significantly lower NCO content. The high viscosity products have a minimum viscosity of 5000, preferably 12,000, and more preferably, 15,000 to 70,000 mPa.s and a maximum viscosity of 100,000, preferably 90,000 and, more preferably, 70,000 mPa.s. The viscosities are determined at 25 ° C in samples having a solids content of 100% and containing less than 2% by weight of monomer or unreacted. In general, products of extremely high viscosity to solids are obtained from cyclic diisocyanates such as isophorone diisocyanate, bis (4-isocyanatocyclohexyl) methane or aromatic diisocyanates previously described. The polyisocyanate mixtures obtained according to the present invention have an average functionality of about 2 to 7, depending on whether a low or high viscosity product is desired. The low viscosity products prepared from aliphatic diisocyanate starting materials have an average functionality of 2 to 4, preferably 2.2 to 3.3, and an NCO content of 10 to 35%, preferably 10 to 25. % and, more preferably, from 12 to 22%. The high viscosity products prepared from aliphatic diisocyanate starting materials have an average functionality of 3 to 7, preferably 3.5 to 6.; an NCO content of 5 to 25%, preferably 10 to 17%, and an equivalent weight which is at least 30% higher, preferably 40% higher and, more preferably, 50% higher than the molecular weight of the monomeric isocyanate used to prepare the polyisocyanate mixture. Products of extremely high viscosity to solids prepared from cyclic diisocyanate starting materials have an average functionality of 2 to 6, preferably 2.2 to 5, and an NCO content of 10 to 40%, preferably 12%. to 25% by weight. The polyisocyanate mixtures according to the invention have a content of isocyanuraph groups (calculated as N3, C3.03, MW 126) of up to 25% in egp, preferably up to 20% by weight. When allophanatization / trimerization catalysts are used, the polyisocyanate mixtures will generally have an isocyanurate group content of at least 5%, preferably at least 10%, in pesb. Even when highly selective allophanatization catalysts are used, smaller amounts of isocyanurate groups are formed. The polyisocyanate mixtures have a content of allophanate groups (calculated as N2, C2, H, 03, PM 101) of at least 5%, preferably at least 10%, by weight. The upper limit for the content of allophanate groups is 35%, preferably 30% by weight. The polyisocyanate mixtures, which are prepared from aliphatic, cycloaliphatic or araliphatic diisocyanate starting materials, especially the low viscosity products prepared from aliphatic diisocyanate starting materials, can be almost colorless, i.e. yellowness index measured on the APHA color scale of 10 to 200, preferably 10 to 150 and, more preferably, 10 to 100. In the low viscosity products prepared from < ie aliphatic diisocyanate starting materials using allophanatization / trimerization catalysts, the r, azone of monoisocyanurate groups to monoalo-fanate groups in the polyisocyanates according to the invention is from about 10: 1 to 1:10, preferably about 5 : 1 to 1: 7. These values can be determined by gel permeation chromatography (CPG) determining the areas under the peaks for monoisocyanurate and monoalphanate groups. According to the present invention, the term "monoisocyanurate" means a polyisocyanate containing an isocyanurate group and which is formed from three diisocyanate molecules and the term "polyisocyanurate" means a polyisocyanate containing more than one isocyanurate group. The term "monoalhopnate" means a polyisocyanate containing an allophanate group and which is formed from two molecules of diisocyanate and 1 monoalcohol molecule and the term "polyalphanate" means a polyisocyanate containing more than one allophanate group. The products according to the present invention are polyisocyanates containing allophanate groups, siloxane groups, preferably in the form of dimethylsiloxane groups and, optionally, isocyanurate groups. The products may also contain residual urethane groups which do not convert to allophanate groups depending on the temperature maintained during the reaction and the degree of consumption of isocyanate groups. Although it is preferred to convert at least 50%, preferably at least 70%, and more preferably at least 90% of the urethane groups formed from the hydroxyl compounds containing siloxane into allophanate groups, it is not necessary that the The number of equivalents of allophanate groups exceeds the number of equivalents of urethane groups and provided that the polyisocyanate mixture contains sufficient allophanate groups to ensure that the polyisocyanate mixture remains stable and homogeneous in storage for 3 months at 25 ° C. If the polyisocyanate mixture contains an insufficient number of allophanate groups, the mixture may be cloudy and a gradual deposition of insoluble constituents may occur during storage. For example, it may not be necessary to convert the urethane groups formed from the siloxane-containing hydroxyl compounds into allophanate groups when the polyisocyanate mixture contains allophanate groups formed from monoalcohols that do not contain siloxane, as discussed previously. The products according to the invention are valuable starting materials for the production of polyaddition products of polyethioacids by reaction with compounds containing at least two isocyanate-reactive groups. The products according to the invention can also be cured by moisture to form coatings. Preferred products are one or two component coating compositions, more preferably polyurethane coating compositions. When the polyisocyanates are not blocked, two-component compositions are obtained. On the contrary, when the polyisocyanates are blocked, one component compositions are obtained. Prior to their use in coating compositions, the polyisocyanate mixtures according to the invention can be mixed with other known polyisocyanates, for example polyisocyanate adducts containing biuret, isocyanurate, allophanate, urethane, urea, carbodiimide and / or uretdione groups. The amount of the polyisocyanate mixtures according to the invention to be mixed with these other polyisocyanates depends on the siloxane content of the polyisocyanates according to the invention, the intended application of the resulting coating compositions and the amount of low energy properties. surface that are desired for this application. To obtain low surface energy properties, the resulting polyisocyanate mixtures should contain a minimum of 0.002% by weight, preferably 0.02% by weight and, more preferably, 0.2% by weight, of siloxane groups (MW 44), based on solids, and a maximum of 10% by weight, preferably 7% by weight and, more preferably, 3% by weight of siloxane groups (PM 44), based on solids. Knowing the siloxane content of the polyisocyanate mixtures according to the invention and the desired siloxane content of the resulting mixtures of polyisocyanates, the relative amounts of the polyisocyanate mixtures and the other polyisocyanates can be easily determined. According to the present invention, any of the polyisocyanate mixtures according to the invention can be mixed with other polyisocyanates. However, the polyisocyanate mixtures to be mixed preferably have a minimum siloxane content of 5% by weight, preferably 10% by weight and, more preferably, 20% by weight, and a maximum siloxane content of 50% by weight. % by weight, preferably 45% by weight. These so-called "concentrates" can then be mixed with other polyisocyanates to form polyisocyanate mixtures that can be used to prepare coatings having low surface energy characteristics. Several advantages are obtained by preparing concentrates with high siloxane contents and subsequently mixing them with polyisocyanates that do not contain siloxane. Initially, it is possible to convert many products into low surface energy polyisocyanates, while only one concentrate is produced. By forming said low surface energy polyisocyanates by mixing commercial polyisocyanates with concentrates, it is not necessary to separately prepare each of the products either in a siloxane-containing form or in a form not containing siloxane. Secondly, it may not be necessary to remove the unreacted starting diisocyanate after the preparation of the concentrates. The commercial polyisocyanates should contain very low amounts of unreacted starting diisocyanate as described above. However, since only small amounts of concentrates with high siloxane contents need to be mixed with polyisocyanates that do not contain siloxane to obtain low surface energy polyisocyanates, the low required levels of unreacted starting diisocyanate can be achieved without having that eliminate these monomers in a costly distillation step. Preferred reaction partners for the products according to the invention are polyhydroxypolyesters, polyhydroxypolyesters, polyhydroxypolyacrylates, polyhydroxypolylactones, polyhydroxy polyurethanes, polyhydroxypoliepoxides and, optionally, low molecular weight polyhydric alcohols known from the technology of polyurethane coatings. The polyamines, particularly in blocked form, for example as polyketimine, oxazolidines or polyaldimines, are also suitable reaction partners for the products according to the invention. Also suitable are polyaspartic acid derivatives (succinates) containing secondary amino groups, which also function as reactive diluents.

To prepare the coating compositions, the amount of the polyisocyanate component and the isocyanate-reactive component is selected to obtain equivalent ratios of isocyanate groups (whether present in blocked form as unblocked) to isocyanate-reactive groups of about 0.8 to 3 -, preferably about 0, 9 to 1.5. To accelerate the hardening, the coating compositions may contain known polyurethane catalysts, for example tertiary amines such as triethylamine, pyridine, methylpyridine, benzyldi-methylamine, N, N-dimethylaminociclohexane, N-methylpiperidine, pentamethyldiethylenetriamine, 1,4-diazabicyclo [ 2, 2, 2] octane and N, N '-dimethylpiperazine, or metal salts such as iron (III) chloride, zinc chloride, zinc-2-ethyl caproate, tin (II) -ethyl caproate, dibutyltin (IV) and molybdenum glycolate. The products according to the invention are also valuable starting materials for one-component coating compositions, preferably polyurethane coating compositions, wherein the isocyanate groups are used in a blocked form by known blocking agents. The blocking reaction is carried out in a known manner by reaction of the isocyanate groups with suitable blocking agents, preferably at an elevated temperature (for example, about 40 to 160 ° C) and, optionally, in the presence of a suitable catalyst, for example the tertiary amines or metal salts previously described. Suitable blocking agents include monophenols such as phenol, cresols, trimethylphene and tert-butylphenols.; tertiary alcohols such as tert-butanol, tere-amyl alcohol and dimethylphenylcarbinol; compounds which readily form enols such as acetoacetic ester, acetylacetone and malonic acid derivatives, for example malonate, diethyl ester; secondary aromatic amines such as N-methylaniline, N-methyl toluidine, N-phenyl toluidine and N-phenylxidine; imides such as succinimide; lactams, such as e-caprolactam and d-valerolactam; pyrazoles such as 3,5-dimethylpyrazole; oximes such as butanone oxime, methyl-amyl ketoxime and cyclohexanone oxime; mercaptans such as methyl mercaptan, ethyl mercaptan, butyl mercaptan, 2-mercaptobenzthiazole, α-naphthyl mercaptan and dodecyl mercaptan, and triazoles such as 1H-1,2,4-triazole. The polyisocyanate mixtures according to the invention can also be used as a polyisocyanate component in water-borne two-component coating compositions. To be useful in these compositions, the polyisocyanate mixtures must be rendered hydrophilic either by mixing with external emulsifiers or by reaction with compounds containing cationic, anionic or nonionic groups. Methods for converting polyisocyanates to hydrophilic are described in the co-pending application, US Pat. 5,194,487 and 5,200,489, the descriptions of which are hereby incorporated by reference. The low surface tension of the modified polyisocyanate mixtures increases the dispersion of pigments and the wetting of substrates. The coating compositions may also contain other additives such as pigments, dyes, fillers, leveling agents and solvents. The coating compositions can be applied to the substrate to be coated in solution or melted by conventional methods such as painting, rollers, pouring or spraying. The coating compositions containing the polyisocyanates according to the invention provide coatings having good drying times, which adhere surprisingly well to a metal base and which are particularly light-stable and color-stable in the presence of heat and very resistant to abrasion. Moreover, they are characterized by high hardness, elasticity, very good resistance to chemical agents, high gloss, good resistance to atmospheric conditions, good resistance to environmental corrosion and good pigmentation qualities. Above all, the coating compositions have excellent surface appearance and excellent cleaning ability. The invention is further illustrated, but without intending to limit it, by way of the following examples, wherein all parts and percentages are by weight, unless otherwise specified. EXAMPLES Alcohol 1 A polydimethylsiloxane polyoxyethylene copolymer having two OH sites per molecule and an average weight of hydroxy equivalents of 1200 (from Dow Corning, Q4-3667 Fluid). Polyisocyanate 1 - According to the invention 100 parts of 1,6-hexamethylene diisocyanate (DIH) and 1.0 part of Alcohol 1 were added to a reactor equipped with a gas sparger, a stirrer and a thermometer and heated at 90 ° C while nitrogen gas was bubbled through it with agitation. To the stirred solution was added 2.02 parts of a 0.5% solution of trimethylbenzylammonium hydroxide catalyst dissolved in ethyl acetate. The addition of the catalyst solution was done at a rate such that the reaction mixture was maintained at about 90 ° C. After the addition of catalyst was complete, the reaction mixture was maintained at 90 ° C for a further 15 minutes (s) and then 0.01 part of di- (2-ethylhexyl) phosphate was added. The mixture had an NCO content of 40.3% The residual monomeric DIH was removed by rotary sheet evaporation and, after filtering (1 miera), a liquid isocyanurate modified with allophanate was obtained having the following properties: Viscosity 4410 mPa .sa 25 ° C Content in NCO 20, 5% Free DIH monomer content 0.3% Silicon content (SiO) 0.38% Liquid surface tension 27.0 dynes / cm. Polyisocyanate 2 (Comparison) A polyisocyanate containing isocyanurate groups prepared from 1,6-hexamethylene diisocyanate (DIH) (from Miles, Inc., as Desmodur N 3300) and having the following properties: Viscosity 3000 mPa.sa 25 ° C Content in NCO 21.6% Content in monomer free DIH <0.2% Silicon content (SiO) 0% Liquid surface tension 48.6 dynes / cm. It is apparent, when comparing the surface tension for Polyisocyanate 2 with that corresponding to Polyisocyanate 1, that the presence of siloxanes is necessary to obtain a low surface tension. Polyisocyanate 3 (Comparison) A polyisocyanate containing isocyanurate groups and allophanate groups was prepared by adding 301.7 parts of hexamethylene diisocyanate and 13.3 parts of 1-butanol to a 3-neck 500 ml flask equipped with a gas sparger, a mechanical agitator, a thermometer and a condenser. The stirred mixture was heated for 1 hour at 60 ° C while dry nitrogen was bubbled through the reaction mixture. The temperature of the reaction mixture was then raised to 90 ° C. 0.214 parts of a 4.4% solution of N, N, N-trimethyl-N-benzylammonium hydroxide in 1-butanol was added to the reaction mixture at 90 ° C. When the reaction mixture reached an NCO content of 34.8%, the reaction was stopped by adding 0.214 parts of di- (2-ethylhexyl) phosphate. The excess monomer was removed by thin layer evaporation to obtain a clear, almost colorless liquid having the following properties: Viscosity 630 mPa.s at 25 ° C NCO content 19.7% Content of free DIH monomer 0.35% Silicon content (SiO) 0% Liquid surface tension 43.3 dynes / cm. It is apparent, by comparing the surface tension for Polyisocyanate 3 with that corresponding to Polyisocyanate 1, that polyisocyanates containing allophanate groups, but not containing siloxane groups, are not suitable for the production of polyisocyanates with low surface tension. Polyisocyanate 4 (Comparison) To a 3-necked flask equipped with a gas bubbler, a mechanical stirrer, a thermometer and a condenser were added 100 parts of Polyisocyanate 2 and 2.2 parts of Alcohol 1. Dry nitrogen was bubbled through the the stirred reaction mixture, while heating at 60 ° C for 2 hours. After cooling to 25 ° C, the reaction mixture was cloudy and contained solid particles. After filtering, a clear and colorless material having the following properties was obtained:Viscosity: 3100 mPa.s at 25 ° C Content in NCO 20.7% Content in free DIH monomer < 0.2% Silicon content (SiO) 0, 64% Liquid surface tension 30.8 dynes / cm. The fact that the product was turbid and contained solid particles and that, after filtering, still had a surface tension greater than the product of Example 1, despite having a higher silicon content, clearly demonstrates the advantage of the groups allophanate (Polyisocyanate 1) on the urethane groups. Polyisocyanate 5 - According to the invention 100 parts of 4,4'-diphenylmethane diisocyanate (DIM), 5.4 parts of n-butanol and 1.0 part of Alcohol 1 were added to a reactor equipped with a stirrer and a thermometer. The reaction mixture was heated to 90 ° C and then 50 ppm of zinc acetylacetonate was added. After about 1 hour, the NCO content was 26.0% by weight. The reaction was terminated by addition of 100 ppm benzoyl chloride and the reaction was cooled to 25 ° C. The resulting turbid and yellow polyisocyanate mixture, containing allophanate groups, had the following properties: Viscosity 122 mPa.s at 25 ° C NCO content 26.0% Silicon content (SiO) 0.30% Liquid surface tension 25 , 4 dynes / cm. Polyisocyanate 6 (Comparison) To a 3-necked flask equipped with a gas bubbler, a mechanical stirrer, a thermometer and a condenser were added 100 parts of DIM and 5.4 parts of 1-butanol. Dry nitrogen was bubbled through the stirred reaction mixture, while heating to 90 ° C. After 2 hours at 90 ° C, 50 ppm of zinc acetylacetonate was added in one portion. When the NCO content reached 26.0%, the reaction was stopped by adding 100 ppm of benzoyl chloride and cooled to 25 ° C. The resulting light yellow polyisocyanate had the following properties: Viscosity 72 mPa.s at 25 ° C NCO content 26.0% Silicon content (SiO) 0% Liquid surface tension 48.7 dynes / cm. It is apparent, by comparing the surface tension for Polyisocyanate 5 with that corresponding to Polyisocyanate 4, that polyisocyanates containing allophanate groups, but not containing siloxane groups, are not suitable for the production of polyisocyanates with low surface tension. Polyisocyanate 7 - According to the invention To a 3-necked flask equipped with a gas sparger, a mechanical stirrer, a thermometer and a condenser were added 100 parts of 4,4'-methylenediphenyl diisocyanate (DIM) and 5.4 parts of 1-butanol. Dry nitrogen was bubbled through the stirred reaction mixture while heating to 90 ° C. After 2 hours at 90 ° C, 50 ppm of zinc acetylacetonate was added in one portion. When the NCO content reached 26.0%, the reaction was stopped by adding 100 ppm of benzoyl chloride and cooled to 60 ° C. To this was added 1.0 parts of Alcohol 1 and the mixture was allowed to react for 2 hours at 60 ° C. The reaction mixture was cooled to 25 ° C and filtered to obtain a turbid, light yellow polyisocyanate, which had the following properties: NCO content 25.6% Silicon (SiO) content 0.28% Liquid surface tension 25.5 dynes / cm. This example demonstrates that it is possible to incorporate siloxane groups through urethane groups and obtain a polyisocyanate having a low surface tension, provided that the polyisocyanate contains more allophanate groups than urethane groups.

Example 1 - According to the invention A coating composition was prepared by mixing a hydroxyl-functional polyacrylate / polyester with a solids content of 70% solids in n-butyl acetate and an equivalent weight of 607 (Desmophen 2945, from Bayer Corp .) with Polyisocyanate 1 at an equivalent NCO: OH ratio of 1.1: 1. The composition was reduced to 70% solids with a solvent mixture containing Exxate 700 (a solvent based on Exxon ester), n-butyl acetate and methylamyl ketone (1: 4: 1) and allowed to react for five minutes. At that moment, a drop of thickness level in wet film of 5 mil in glass was prepared and allowed to cure for two weeks at 70 ° F and 55% relative humidity. The resulting coating was transparent and had a surface energy of 24.9 dynes / cm. Example 2 (Comparison) Example 1 was repeated with the exception that the Comparative Polyisocyanates 2 and 3 were used separately in place of Polyisocyanate 1. The resulting coatings were clear, but had surface energies of 43.7 and 43.6 dynes / cm, respectively. It is apparent when comparing these surface energies with the surface energy of Example 1 that it is necessary that the polyisocyanate component contains both allophanate groups and siloxane groups to obtain coatings having low surface energies. Example 3 (Comparison) A coating composition was prepared by blending a hydroxyl functional polyacrylate / polyester having a solids content of 70% solids in n-butyl acetate and an equivalent weight of 607 (Desmophen 2945, from Bayer Corp. ) with Polyisocyanate 4 at an equivalent NCO: OH ratio of 1.1: 1. The composition was reduced to 70% solids with a solvent mixture containing Exxate 700 (a solvent based on Exxon ester), n-butyl acetate and methylamyl ketone (1: 4: 1) and allowed to react for five minutes. At that time, a drop of thickness level in wet film of 5 mil in glass was prepared and allowed to cure for two weeks at 70 ° F and 55% relative humidity.

The resulting coating was slightly cloudy and had a surface energy of 30.2 dynes / cm. The fact that the coating was turbid and also had a higher surface energy than the coating of Example 1, clearly demonstrates the advantage of incorporating siloxane groups through allophanate groups as opposed to urethane groups. Example 4 - According to the invention 90 parts of a hydroxy-functional polyester with a solids content of 100% and an equivalent weight of 340 (Desmophen 1150, Bayer Corp.) were mixed with 10 parts of a drying paste (Baylith L, from Bayer Corp.) and allowed to digest overnight. A coating composition was prepared by mixing this mixture with Polyisocyanate 5 at an NCO: OH equivalent ratio of 1.05: 1. The composition was allowed to digest for a period of five minutes and then a thin film thickness level drop of 5 mil was prepared in cold rolled steel and allowed to cure for two weeks at 70 ° F and 55% humidity relative. A clear, light brown coating was obtained, which had a surface energy of 26.3 dynes / cm. Example 5 (Comparison) Example 4 was repeated, with the exception that Comparative Polyisocyanate 6 was used in place of Polyisocyanate 5. The resulting coating was clear, but had a surface energy of 41.6 dynes / cm. It is apparent when comparing this surface energy with the surface energy of Example 3 that it is necessary that the polyisocyanate component contains both allophanate groups and siloxane groups to obtain coatings having low surface energies. Example 6 - According to the invention 90 parts of a hydroxy-functional polyester having a solids content of 100% and an equivalent weight of 340 (Desmophen 1150, Bayer Corp.) were mixed with 10 parts of a drying paste (Baylith L , from Bayer Corp.) and allowed to digest overnight. A coating composition was prepared by mixing this mixture with Polyisocyanate 7 at an NCO: OH equivalent ratio of 1.05: 1. The composition was allowed to digest for a period of five minutes and then a thin film thickness level decrease of 5 mil was made in cold rolled steel and allowed to cure for two weeks at 70 ° F and 55% relative humidity . A transparent, light brown coating was obtained, which had a surface energy of 26.9 dynes / day. This example demonstrates that it is possible to incorporate siloxane groups through urethane groups to obtain a low surface energy coating, provided that the polyisocyanate contains more allophanate groups than urethane groups. Surface tension and surface energy measurements All the stresses of given liquid (resin) surfaces (in dynes / cm) were obtained using the duNouy or o-ring method. In this static method, the force applied to a thin platinum ring was waved using a tensiometer. All energies of given solid surfaces (film) (in dynes / cm) were obtained using the Owens-Wendt procedure. The contact angle of two solvents (water and methylene iodide) was measured with a goniometer. Several readings were taken and the average was found. The means were then used to calculate the solid surface energy of the coating, considering the contributions of the polar and dispersive forces. Although the invention has been described in detail in the foregoing for purposes of illustration, it is to be understood that such detail has only that purpose and that those skilled in the art can make variations therein without departing from the spirit and scope of the invention, except in what may be limited by the claims.

Claims (20)

1. RE-INVINATIONS 1. A mixture of polyisocyanates which i) has an NCO content of 5 to 35% by weight and is prepared from an organic diisocyanate, ii) contains up to 25% by weight of isocyanurate groups (calculated as N3, C3 , 03 / PM 126), iii) contains allophanate groups in an amount such that there are more equivalents of alofanate groups than of urethane and urea groups and such that the polyisocyanate mixture remains stable and homogeneous in storage for 3 months at 25 °. C and iv) contains siloxane groups (calculated as SiO, MW 44) in an amount of 0.002 to 50% by weight, where the above percentages are based on the solids content of the polyisocyanate mixture, excluding any unreacted organic diisocyanate, and wherein the siloxane groups are incorporated by reaction of an isocyanate group with a compound containing two or more isocyanate-reactive groups directly attached to carbon atoms and one or more siloxane groups.
2. 2. The polyisocyanate mixture of Claim 1, wherein said organic diisocyanate consists of 1,6-hexamethylene diisocyanate.
3. 3. The polyisocyanate mixture of Claim 1, which contains less than 10% by weight, based on solids, of siloxane groups.
4. 4. The polyisocyanate mixture of Claim 2, which contains less than 10% by weight, based on solids, of siloxane groups.
5. The polyisocyanate mixture of Claim 3, which has a viscosity of less than 5000 mPa.s at 25 ° C and a siloxane group content of 20 to 50% by weight.
6. 6. The polyisocyanate mixture of Claim 4, which has a viscosity of less than 5000 mPa.s a 25 ° C and a content in siloxane groups of 20 to 50% by weight.
7. 7. The polyisocyanate mixture of claim 1, having an isocyanurate group content of at least 5% by weight, based on the solids.
8. The polyisocyanate mixture of Claim 2, which has an isocyanurate group content of at least 5% by weight, based on the solids.
9. 9. The polyisocyanate mixture of Claim 3, having an isocyanurate group content of at least 5% by weight, based on the solids.
10. The polyisocyanate mixture of Claim 4, which has an isocyanurate group content of at least 5% by weight, based on the solids.
11. 11. The polyisocyanate mixture of Claim 5, having an isocyanurate group content of at least 5%, based on the solids.
12. 12. The polyisocyanate mixture of Reivinication 6, having an isocyanurate group content of at least 5%, based on the solids.
13. 13. A mixture of polyisocyanates that i) has an NCO content of 5 to 35% by weight, based on solids, and is prepared from an organic diisocyanate, ii) contains up to 25% by weight, based on the solids, of isocyanurate groups (calculated as N3, C3.03, MW 126), iii) contains allophanate groups in an amount such as there are more equivalents of allophanate groups than of urethane and urea groups and such that the mixture of polyisocyanates remains stable and homogeneous in storage for 3 months at 25 ° C and iv) contains siloxane groups (calculated as SiO, PM 28) in an amount of 0.002 to 50% by weight, based on solids, where the The above percentages are based on the solids content of the polyisocyanate mixture, excluding any unreacted organic diisocyanate, and where the siloxane groups are incorporated by reaction of an isocyanate group with a compound containing two or more hydroxyl groups directly attached to the isocyanate group. one carbon atom and two or more siloxane groups in the form of -Si (CH3) 20- groups.
14. 14. The polyisocyanate mixture of Claim 13, wherein said organic diisocyanate consists of 1,6-hexamethylene diisocyanate.
15. 15. The polyisocyanate mixture of Claim 13, which contains less than 10% by weight, based on solids, of siloxane groups.
16. 16. The polyisocyanate mixture of Claim 14, which contains less than 10% by weight, based on solids, of siloxane groups.
17. 17. The polyisocyanate mixture of Claim 13, which has a viscosity of less than 5000 mPa.s at 25 ° C and a siloxane group content of 20 to 50% by weight.
18. 18. The polyisocyanate mixture of Claim 14, which has a viscosity of less than 5000 mPa.s at 25 ° C and a siloxane group content of 20 to 50% by weight.
19. 19. A process for the production of a polyisocyanate mixture which i) has an NCO content of 5 to 35% by weight and is prepared from an organic diisocyanate, ii) contains up to 25% by weight of isocyanurate groups ( calculated as N3, C3.03, MW 126), iii) contains allophanate groups in an amount such that there are more equivalents of alofanate groups than of urethane and urea groups and such that the mixture of polyisocyanates remains stable and homogeneous in storage during 3 months at 25 ° C and iv) contains siloxane groups (calculated as SiO, MW 44) in an amount of 0.002 to 50% by weight, where the above percentages are based on the solids content of the polyisocyanate mixture, excluding any unreacted organic diisocyanate, by a) reaction of a portion of the isocyanate groups of an organic diisocyanate with 0.01 to 250 millimoles, per mole of organic diisocyanate, of a compound containing two or more reactive groups isocyanate groups directly attached to the carbon atoms and one or more siloxane groups and, optionally, a monofunctional or polyfunctional alcohol containing no siloxane to form urethane groups and, optionally, urea groups, provided at least one of the compounds isocyanate reagents contain hydroxyl groups; b) addition of an allophanatization catalyst and, optionally, a trimerization catalyst before, during or after step a); c) conversion of a sufficient amount of the urethane groups formed in step a) into allophanate groups to satisfy the requirements of iii); d) completion of the allophanatization and trimerization reaction to the desired NCO content by adding a catalyst poison and / or thermally deactivating the catalyst, and e) eventual removal of the unreacted organic diisocyanate.
20. 20. A one or two component coating composition containing the polyisocyanate mixture of Claim 1, optionally blocked by blocking agents for isocyanate groups, and a compound containing isocyanate-reactive groups. SUMMARY OF THE DESCRIPTION The present invention is directed to a mixture of polyisocyanates which i) has an NCO content of 5 to 35% by weight and is prepared from an organic diisocyanate, ii) contains up to 25% by weight of groups isocyanurate (calculated as N3, C3.03, MW 126), iii) contains allophanate groups in an amount such that there are more equivalents of alofa nato groups than of urethane and urea groups and such that the mixture of polyisocyanates remains stable and homogeneous in storage for 3 months at 25 ° C and iv) contains siloxane groups (calculated as SiO, MW 44) in an amount of 0.002 to 50% by weight, where the above percentages are based on the solids content of the polyisocyanate mixture, excluding any unreacted organic diisocyanate, and where the siloxane groups are incorporated by reaction of an isocyanate group with a compound containing two or more isocyanate-reactive groups directly attached to the atoms of carbon and one or more siloxane groups. The present invention is also directed to a process for producing this mixture of polyisocyanates and to their use, optionally in blocked form, as an isocyanate component in one or two component coating compositions.