Coating agents having high scratch resistance and weathering stability

[0001] The present invention relates to a thermally curable coating agent with high scratch resistance based on aprotic solvents, containing polyols and polyisocyanates with structural units of different alkoxysilane functionality.

[0002] WO-A-01/98393 describes 2K coating agents containing polyols as film-forming agents and as a cross-linking component of polyisocyanate, which is partially functionalized with alkoxysilyl groups. These coating agents are used as prime agents and are optimized for adhesion to metallic substrates, in particular aluminum substrates. Basic coating systems clearcoat are applied to these coatings in the process of serial OEM or refinishing painting. The coating compositions according to WO 01/98393 are not optimized in terms of scratch resistance and weather resistance.

[0003] EP-A-0 994 117 describes moisture-curable mixtures that contain a polyol component and a polyisocyanate component that can partially react with monoalkoxysilylalkylamine, preferably to aspartate. The coatings of such mixtures have a certain hardness, but in terms of resistance to weather conditions and in particular scratch resistance they have limited suitability for OEM applications.

[0004] US-A-2006/0217472 describes coating agents that may contain hydroxyl functional acrylate, low molecular weight polyol component, polyisocyanate and amino functional alkoxysilyl component, preferably bi-alkoxysilylamine. Such coating agents are used as a clearcoat in basecoat-clearcoat systems and lead to scratch-resistant coatings. However, such coating agents have only very limited storage stability, and the coatings formed therefrom have little resistance to weathering, in particular to UV radiation in the wet-dry cycle.

[0005] WO 2006/042585 describes colorless lacquers suitable for serial OEM lacquering, which as the main film-forming component contain polyisocyanates whose isocyanate groups have reacted with bisalkoxysilylamine, preferably to an extent greater than 90 mol%. Such clearcoats have excellent scratch resistance, while being highly resistant to chemicals and weathering. However, there is still a need to further increase the resistance to atmospheric agents, in particular to the formation of cracks under the influence of UV radiation in the wet-dry cycle, while maintaining a high level of scratch resistance.

[0006] EP-A-1 273 640 describes 2K coating agents consisting of a polyol component and a crosslinking component consisting of aliphatic and / or cycloaliphatic polyisocyanates, with 0.1 to 95 mole% of the initially free groups present isocyanate reacted with bisalkoxysilylamine. These coatings can be used for OEM OEM serial painting and have good scratch resistance with good environmental impact. However, these coating agents have a particularly strong tendency for secondary cross-linking, since the degree of reaction in thermal curing after application is insufficient. This has a particularly negative impact on weather resistance.

Problem and solution [0007] The problem of the present invention was to provide coating agents, in particular for use as a transparent varnish layer in the process of serial OEM painting and refinishing painting of cars, which lead to crosslinked coatings that are highly weather-resistant. whereby the undesirable formation of groups resistant to hydrolysis and atmospheric agents is inhibited as far as possible in order to ensure high resistance to acids. In addition, coating agents should provide coatings that are highly scratch resistant and in particular have high gloss when exposed to scratches. In addition, it should be possible to produce coatings and varnish coatings, especially colorless varnish coatings, even with a layer thickness> 40 gm, without stress cracks. This is an important condition for the use of coatings and paint coats, especially colorless paint coats, in the technologically and aesthetically demanding field of serial car painting (OEM).

[0008] In particular, colorless varnish coatings with high resistance should be provided, in particular against cracking when exposed to atmospheric agents with UV radiation in the dry and dry cycle, in combination with excellent scratch resistance.

[0009] In addition, new coating agents should be manufactured in an easy and well reproducible manner and should not create ecological problems when applying the coating material.

Solution to the problem [0010] In the light of the above-mentioned problems, coating agents based on aprotic solvents containing at least one compound (A) containing hydroxyl groups and at least one compound (B) containing isocyanate groups have been developed, characterized in that one or more components the coating agent as additional functional components contains from 2.5 to 97.5 mol%, calculated on the total of structural units (I) and (II), at least one structural unit (I) of the formula

-N (X-SiR''x (OR ') 3-x) n (X'-SiR''y (OR') 3-y) m (I) in which

R '= hydrogen, alkyl or cycloalkyl, the carbon atom chain may be separated by non-contiguous oxygen, sulfur or NRa groups,

X, X '= linear and / or branched alkylene or cycloalkylene group with 1 to 20 carbon atoms,

R '' = alkyl, cycloalkyl, aryl or aralkyl, wherein the chain of carbon atoms may be separated by non-adjacent oxygen, sulfur or NRa groups, n = 0 to 2, m = 0 to 2, m + n = 2, and x, y = 0 to 2, and from 2.5 to 97.5 mol%, calculated on the total of structural units (I) and (II), of at least one structural unit (II) of formula

-Z- (X-SiR '' x (OR ') 3-x) (II) in which

Z = -NH-, -NR-, -O- z

R = hydrogen, alkyl, cycloalkyl, aryl or aralkyl, wherein the chain of carbon atoms may be separated by non-contiguous oxygen, sulfur or NRa groups, with Ra = alkyl, cycloalkyl, aryl or aralkyl,

R '= hydrogen, alkyl or cycloalkyl, the carbon atom chain may be separated by non-contiguous oxygen, sulfur or NRa groups,

X = linear and / or branched alkylene or cycloalkylene group with 1 to 20 carbon atoms,

R '' = alkyl, cycloalkyl, aryl or aralkyl, wherein the chain of carbon atoms may be separated by non-adjacent oxygen, sulfur or NRa groups, x = 0 to 2, and the polyol (A) contains at least one poly (meth) acrylate polyol.

[0011] Coating agents are preferred in which one or more coating agent ingredients contain as additional functional ingredients from 5 to 95 mole%, especially from 10 to 90 mole%, particularly preferably from 20 to 80 mole%, and even more preferably from 30 to 70 mole%, in each case based on the total structural units (I) and (II), at least one structural unit of formula (I) and from 5 to 95 mole%, in particular from 10 to 90 mole%, particularly preferably from 20 to 80 mole%, and even more preferably from 30 to 70 mole%, in each case based on the total structural units (I) and (II) of at least one structural unit of formula (II).

[0012] Given the state of the art, it was surprising and unpredictable for the skilled person that the problems underlying the present invention could be solved by the coating means according to the invention.

[0013] The ingredients according to the invention can be produced particularly easily with very good reproducibility and do not cause significant toxicological and ecological problems when applying the varnish.

[0014] The coating compositions according to the invention provide new coatings and varnish coatings, especially colorless varnish coatings that are very scratch resistant and, unlike the commonly used high crosslinked scratch resistant systems, are acid resistant. In addition, it is possible to produce coatings and varnish coatings, especially colorless varnish coatings, even with a layer thickness> 40 μm, without the appearance of stress cracks. It is therefore possible to use the coatings and paint coats according to the invention, especially the colorless paint coats, in the technologically and aesthetically demanding field of serial car painting (OEM). At the same time, they are characterized by particularly high resistance during washing in car washes and resistance to scratches. In particular, high scratch resistance of the coatings is obtained immediately after curing of the coatings, so that the coatings can be handled without problems immediately after curing. In addition, the coatings according to the invention resist cracking under the action of UV radiation and in the wet-dry cycle in the CAM180 test (in accordance with DIN EN ISO 11341 February 98 and DIN EN ISO 4892-2 November 00), combined with high scratch resistance .

Description of the invention

Compound (A) containing hydroxyl groups [0015] Low molecular weight polyols as well as oligomers and / or polymeric polyols are preferably used as compounds (A) containing hydroxyl groups, wherein polyol (A) contains at least one poly (meth) an acrylate.

[0016] Low molecular weight polyols are, for example, diols, preferably such as ethylene glycol, neopentyl glycol, 1,2-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol , 1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and 1,2-cyclohexanedimethanol, and polyols, preferably such as trimethylol ethane, trimethylol propane, trimethylolhexane , 1,2,4 butanetriol, pentaerythritol and dipentaerythritol.

[0017] Preferably, such low molecular weight polyols are mixed with a small amount of oligomers and / or polymers of the polyol component (A).

[0018] Preferred oligomers and / or polymeric polyols (A) have a weight average molecular weight Mw> 500 Dalton, measured by GPC (gel permeation chromatography), preferably between 800 and 100000 Dalton, especially between 1000 and 50,000 Dalton. Particularly preferred are polyacrylate polyols and / or polymethacrylate polyols and their mixed polymers, hereinafter referred to as polyacrylate polyols. The polyols preferably have an OH number of 30 to 400 mg KOH / g, in particular 100 to 300 KOH / g. The glass transition temperatures of polyols, as measured by DSC (differential thermal analysis), are preferably in the range of -150 to 100 ° C, in particular from -120 ° C to 80 ° C. The polyacryl polyols used according to the invention are usually copolymers and have a weight average molecular weight MW from 1000 to 20,000 Dalton, especially from 1500 to 10,000 Dalton, in each case measured by gel permeation chromatography (GPC), relative to the polystyrene standard. The glass transition temperatures of the copolymers are usually in the range from -100 to 100 ° C, particularly preferably from 50 ° C to 80 ° C (measured by DSC measurements). The polyacrylate polyols preferably have an OH number of 60 to 250 mg KOH / g, in particular 70 to 200 KOH / g and an acid number of 0 to 30 mg KOH / g.

[0020] The hydroxyl number (OH number) indicates how much mg of potassium hydroxide is equivalent to the amount of acetic acid that binds when acetylating 1 g of the substance. For the determination, the sample is boiled with acetic anhydride-pyridine and the acid formed is titrated with a potassium hydroxide solution (DIN 53240-2).

The acid number here indicates the number of mg potassium hydroxide that is used to neutralize 1 g of a given compound of component (b) (DIN EN ISO 2114).

[0022] Hydroxyalkyl acrylates and / or hydroxyalkyl methacrylates, preferably in particular 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, are preferably used as monomer units containing hydroxyl groups. 3-hydroxypropyl, 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate and in particular 4-hydroxybutyl acrylate and / or 4-hydroxybutyl methacrylate.

[0023] As other monomer units for polyacrylate polyols, alkyl methacrylates and / or alkyl methacrylates are preferably used, such as in particular ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, , isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, amyl acrylate, amyl methacrylate, hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, 3,3,5-trimethylhexyl acrylate, 3,3,5-trimethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate, lauryl acrylate or lauryl methacrylate, cycloalkyl acrylates and / or cycloalkyl methacrylates such as cyclopentyl acrylate isobornyl, isobornyl methacrylate or in particular cyclohexyl acrylate and / or cyclohexyl methacrylate.

As other monomer units for polyacrylate polyols, vinyl aromatic hydrocarbons such as vinyl toluene, alpha-methylstyrene or in particular styrene, amides or nitriles of acrylic acid or methacrylic acid, vinyl esters or vinyl ethers, and in small amounts especially acrylic acid and / or methacrylic acid.

[0025] In another embodiment of the invention, compound A containing hydroxyl groups in addition to hydroxyl groups contain structural units of formula (I) and / or of formula (II).

[0026] Structural units of formula (I) may be introduced into compound (A) by incorporating monomeric units containing such structural units or by reacting polyols containing other functional groups with a compound of formula (Ia)

HN (X-SiR '' x (OR ') 3-x) n (X'-SiR' '(OR') 3-y) m (Ia), where the substituents have the above meanings. In the case of the polyol reacting with compound (Ia), the polyol has suitable other functional groups that react with the secondary amine group of compound (Ia), in particular acid or epoxy groups. Preferred compounds (Ia) according to the invention are bis (2-ethyltrimethoxysilyl) amine, bis (3-propyltrimethoxysilyl) amine, bis (4-butyltrimethoxysilyl) amine, bis (2-ethyltriethoxysilyl) amine, bis (3-propyltriethoxysilyl) amine or bis (4-butyltriethoxysilyl) amine.

Bis (3-propyltrimethoxysilyl) amine is particularly preferred. Such aminosilanes are available under the trade name DYNASILAN® from DEGUSSA or Silquest® from OSI. [0027] Monomeric units having structural elements (I) are preferably reaction products of acrylic acid and / or methacrylic acid or alkyl acrylates and / or alkyl methacrylates containing epoxy groups with the above-mentioned compounds (Ia).

[0028] Structural units of formula (II) may be introduced into compound (A) by incorporation of monomeric units containing such structural units or by the reaction of polyols containing other functional groups with the compound of formula (IIa)

HZ- (X-SiR''x (OR ') 3-x) (IIa), in which they have the above meanings. In the case of the reaction of the polyol with compound (Ia), the polyol has suitable other functional groups that react with the -ZH functional group of compound (IIa), in particular acid, epoxy or ester groups. Preferred compounds (IIa) according to the invention are omega-aminoalkyl- or omega-hydroxyalkyltrialkoxysilanes, preferably 2-aminoethyltrimethoxysilane, 2-aminoethyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 4-aminobutyltrimethoxysiloxy -hydroxyethyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 4-hydroxybutyltrimethoxysilane, 4-hydroksybutylotrietoksysilan. Particularly preferred compounds (IIa) are N- (2- (trimethoxysilyl) ethyl) alkylamine, N- (3- (trimethoxysilyl) propyl) alkylamine, N- (4- (trimethoxysilyl) butyl) alkylamine, N- (2- (triethoxysilyl) ) ethyl) alkylamine, N- (3- (triethoxysilyl) propyl) alkylamine and / or N- (4- (triethoxysilyl) butyl) alkylamine. N- (3- (trimethoxysilyl) propyl) butylamine is most preferred. Such aminosilanes are available, for example, under the trade name DYNASILAN® from DEGUSSA or Silquest® from OSI.

[0029] Monomeric units having structural elements (II) are preferably reaction products of acrylic acid and / or methacrylic acid or alkyl acrylates and / or alkyl methacrylates containing epoxy groups, in particular with the above-mentioned alkoxysilyl (IIa) compounds with hydroxyl and / or amino functional groups.

Compounds (B) containing isocyanate groups [0030] Di- and / or polyisocyanates that serve as basic structures for the compounds (B) preferably containing the isocyanate groups preferably used according to the invention are preferably known as such, substituted or unsubstituted aromatic, aliphatic, cycloaliphatic and / or heterocyclic polyisocyanates. Examples of preferred polyisocyanates are: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenylmethane4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, p-phenylenediisocyanate, biphenyldiisocyanate, 3,3'-dimethyl-4,4'-diphenyldiamethylene diisocyanate 1,4-diisocyanate, hexamethylene-1,6-diisocyanate, 2,2,4-trimethylhexane-1,6-di-isocyanate, isophorone diisocyanate, ethylenediisocyanate, 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane- 1,3-diisocyanate, cyclohexane-1,4-diisocyanate, methylcyclohexyl diisocyanates, hexahydrotoluene-2,4-diisocyanate, hexahydrotoluene-2,6-diisocyanate, hexahydrophenylene-1,3-diisocyanate, hexahydrophenylene-1,4-diisocyanate, perhydrodiphenylmethane-2,4'-diisocyanate e.g. Desmodur® W from Bayer AG), tetramethyloxy diisocyanates (e.g. TMXDI® from American Cyanamid) and mixtures of the above-mentioned polyisocyanates. In addition, preferred polyisocyanates are biuret dimers and isocyanurate trimers of the above-mentioned diisocyanates.

[0031] Particularly preferred PI polyisocyanates are hexamethylene-1,6-diisocyanate, isophorone diisocyanate and 4,4'-methylenedicyclohexyl diisocyanate, their biuret dimers and / or isocyanurate trimers.

[0032] In another embodiment of the invention, the polyisocyanates are polyisocyanate prepolymers containing urethane structural units, which are obtained by reacting polyols with a stoichiometric excess of said polyisocyanates. Such polyisocyanate prepolymers are described, for example, in US-A-4,581,131.

[0033] According to the invention, the isocyanate groups containing compounds (B), most preferably functionalized with structural units (I) and (II), are particularly preferably prepared by reacting the aforementioned di- and / or polyisocyanates with the aforementioned compounds (Ia) and (IIa ) by reacting from 2.5 to 90 mole%, preferably 5 to 85 mole%, particularly preferably 7.5 to 80 mole% of isocyanate groups in the basic polyisocyanate structure with at least one compound (Ia) and from 2.5 to 90 mole%, preferably 5 to 85 mole%, particularly preferably 7.5 to 80 mole% groups isocyanate in a basic polyisocyanate structure with at least one compound (IIa).

[0034] The total proportion of isocyanate groups reacted with compounds (Ia) and (IIa) in the polyisocyanate compound (B) is in the range from 5 to 95 mole%, preferably from 10 to 90 mole%, particularly preferably from 15 to 85 mole% isocyanate groups in the basic polyisocyanate structure.

[0035] Particularly preferred compounds (Ia) are bis (2-ethyltrimethoxysilyl) amine, bis (3-propyltrimethoxysilyl) amine, bis (4-butyltrimethoxysilyl) amine, bis (2-ethyltriethoxy9 silyl) amine, bis (3-propyltriethoxysilyl) amine and / or bis (4-butyltriethoxysilyl) amine. Bis (3-propyltrimethoxysilyl) amine is particularly preferred. Such aminosilanes are available, for example, under the trade name DYNASILAN® from DEGUSSA or Silquest® from OSI.

[0036] Preferred compounds (IIa) are 2-aminoethyltrimethoxysilane; 2-aminoethyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 3-hydroxypropyltriethoxysilane

4-hydroxybutyltrimethoxysilane, 4-hydroxybutyltriethoxysilane. Particularly preferred compounds (IIa) are N- (2- (trimethoxysilyl) ethyl) alkylamine, N- (3- (trimethoxysilyl) propyl) alkylamine, N- (4- (trimethoxysilyl) butyl) alkylamine, N- (2- (triethoxysilyl) ) ethyl) alkylamine, N- (3- (triethoxysilyl) propyl) alkylamine and / or N- (4- (triethoxysilyl) butyl) alkylamine. N- (3- (trimethoxysilyl) propyl) butylamine is most preferred. Such aminosilanes are available, for example, under the trade name DYNASILAN® from DEGUSSA or Silquest® from OSI.

[0037] The most preferred compounds (B) containing isocyanate groups are reaction products of hexamethylene-1,6-diisocyanate and / or isophorone diisocyanate and / or their isocyanurate trimers with bis (3-propyltrimethoxysilyl) amine and N- (3- (trimethoxysilyl) propyl) butylamine.

[0038] The reaction of compounds (B) containing isocyanate groups with compounds (Ia) and (IIa) preferably takes place in an inert gas atmosphere at a maximum temperature of 100 ° C, preferably a maximum of 60 ° C.

[0039] Free isocyanate groups of compounds (B) containing isocyanate groups may also be used in blocked form. This is preferably the case when the coating agents of the invention are used as one-component systems. In principle, any blocking agent used to block polyisocyanates having a sufficiently low unblocking temperature can be used for blocking. Such blocking agents are well known to the skilled person. Preferably, the blocking agents described in EP-A-0 626 888 and EP-A-0 692 007 are used.

Combination of components A and B and other coating agent components [0040] The weight proportion of compounds A containing hydroxyl groups used, calculated on the weight share of compounds B containing isocyanate groups, depends on the hydroxyl equivalent weight of the polyol and the weight equivalent equivalent of free isocyanate groups of polyisocyanate B.

[0041] It is important for the invention that the coating agent according to the invention contains

2.5 to 97.5 mole% of structural units I, calculated on the sum of structural units I and II, and 2.5 to 97.5 mole% of structural units II, calculated on the sum of structural units I and II.

[0042] The coating compositions according to the invention preferably contain from 2.5 to 97.5% by weight, particularly preferably from 5 to 95% by weight, more preferably from 10 to 90% by weight, especially from 20 to 80% by weight. compounds (A) containing hydroxyl groups, based on the content of non-volatile substances in the coating agent, and preferably from 2.5 to 97.5% by weight, particularly preferably from 5 to 95% by weight, even more preferably from 10 to 90% by weight, especially from 20 to 80% by weight, of compounds (B) containing isocyanate groups, based on the content of non-volatile substances in the coating agent.

Calculated on the sum of functional groups important for crosslinking in the coating agent according to the invention, formed from the shares of hydroxyl and isocyanate groups and the shares of structural elements (I) and (II), the content of structural elements (I) and (II) is preferably from 2.5 to 97.5 mole%, particularly preferably from 5 to 95 mole%, and even more preferably from 10 to 90 mole%.

[0044] In order to further increase the resistance of the coatings according to the invention to the formation of cracks under the action of UV radiation and in the wet-dry cycle in the CAM180 test (according to DIN EN ISO 11341 February 98 and DIN EN ISO 4892-2 November 00), in combination with high scratch resistance immediately after the final thermal cure, high gloss and good gloss retention after weathering, it is also preferred to select such a high content of structural elements (I) and / or (II) and / or (III) that the coating agents according to the invention contain less than 6.5% by mass Si of structural elements (I) and / or (II) and / or (III), more preferably not more than 6% by mass Si of structural elements (I) and / or (II) and / or (III), in each case based on the solids content of the coating agent. The silane content in mass% of Si is determined computationally, on the basis of the amount of compounds having structural unit (I) or compounds (IIa) or (IIIa) used.

In a further embodiment of the invention, structural elements (I) and / or (II) may additionally be part of one or more other components (C) differing from components (A) and (B), the above-mentioned being used criteria. As component (C), oligomers or polymers containing alkoxysilyl groups such as, for example, poly (meth) acrylates mentioned in patent applications US-A-4 499 150, US-A-4 499 151 or EP-A-0 571 can be used, for example 073 as carriers of structural elements (II) or compounds mentioned in WO-A-2006/042585 as carriers of structural elements (I). Such components (C) are usually used in an amount of up to 40% by weight, preferably up to 30% by weight, particularly preferably up to 25% by weight, based on the non-volatile components of the coating agent.

[0046] The weight proportions of polyol A and polyisocyanate B are preferably selected in such a way that the molar equivalent ratio of unreacted isocyanate groups of compounds (B) containing isocyanate groups to hydroxyl groups of compounds (A) containing hydroxyl groups ranges from 0.9: 1 to 1: 1.1, preferably from 0.95: 1 to 1.05: 1, particularly preferably from 0.98: 1 to 1.02: 1.

[0047] As regards one-component coating agents, those compounds (B) containing isocyanate groups whose free isocyanate groups are blocked by the blocking agents described above are selected.

In the case of the 2-component (2K) coating compositions preferred according to the invention, shortly before applying the coating agent, the varnish component containing compound (A) containing hydroxyl groups and other components described below are mixed in a known manner with another varnish component containing compound ( B) containing isocyanate groups and optionally other components described below, usually the varnish component which contains compound (A), contains a catalyst and some solvent.

[0049] As catalysts for crosslinking alkoxysilyl units and the reaction between compound (A) containing hydroxyl groups and compound (B) containing isocyanate groups, known as such compounds can be used. Examples are Lewis acids (electron-deficient compounds) such as, for example, tin naphthenate, tin benzoate, tin octoate, tin butyrate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin oxide, lead octanate and the catalysts described in WO-A-2006/042585. Amine adducts of phosphoric acid or sulfonic acid (e.g., Nacure type from King Industries) are preferably used as crosslinking catalysts for alkoxysilyl units.

[0050] As catalysts, phosphorus-containing catalysts, especially phosphorus and nitrogen, are particularly preferably used. Mixtures of two or more catalysts can also be used.

[0051] Examples of suitable phosphorus-containing catalysts are substituted phosphonic acid diesters and diphosphonic acid diesters, preferably from the group consisting of acyclic phosphonic acid diesters, cyclic phosphonic acid diesters, acyclic diphosphonic acid diesters and cyclic diphosphonic acid diesters. Such catalysts are described, for example, in German Patent Application DE-A-102005045228.

[0052] However, even more preferably, substituted phosphoric acid monoesters and phosphoric acid diesters are used, preferably from the group consisting of acyclic phosphoric acid diesters and cyclic phosphoric acid diesters, particularly preferably amine adducts of monoesters and phosphoric acid diesters. In particular, suitable amino-blocked phosphoric acid esters, preferably amino-blocked ethylhexyl phosphoric acid esters and amino-blocked phenyl phosphoric acid esters, particularly preferably amino-blocked bis (2-ethylhexyl) phosphoric esters are used.

The catalysts are preferably used in an amount of from 0.01 to 20% by weight, particularly preferably in an amount of from 0.1 to 10% by weight, based on the volatile components of the coating agent of the invention. The low efficiency of the catalyst can be partly compensated by the use of correspondingly larger amounts.

[0054] Suitable solvents for the coating agents according to the invention are, in particular, those solvents which in the coating medium are chemically inert towards compounds (A) and (B) and do not react with (A) and (B) when the coating agent cures. Examples of such solvents are aliphatic and / or aromatic hydrocarbons such as toluene, xylene, solvent naphtha, Solvesso 100 or Hydrosol® (from ARAL), ketones such as acetone, methyl ethyl ketone or methyl amyl ketone, esters such as ethyl acetate, butyl acetate, pentyl acetate or ethyl ethoxypropionate, ethers or mixtures of the above-mentioned solvents. Preferably the water content of aprotic solvents or solvent mixtures is a maximum of 1% by weight, particularly preferably a maximum of 0.5% by weight, based on the solvent.

In addition to compounds (A), (B) and (C), other film-forming substances can be used which preferably react with the hydroxyl groups of compound (A) and / or with the free isocyanate groups of compound (B) and / or with alkoxysilyl groups compounds (A), (B) and / or (C) and can form points of the crosslinked structure.

[0056] As component (D), amino resins and / or epoxy resins can be used, for example. Contemplated are conventional and known amino resins whose methylol and / or methoxymethyl groups may be partially functionalized by carbamate and allophanate groups. Such cross-linking agents are described in US-A-4 710 542 and EP-B-0 245 700 and in article B. Singh and colleagues of "Carbamylmetylated Melamines, Novel Crosslinkers for the Coatings Industry" in the Advanced Organic Coatings Science and Technology Series, 1991, vol. 13, pages 193 to 207.

[0057] Typically, such components (D) are used in an amount of up to 40% by weight, preferably up to 30% by weight, particularly preferably up to 25% by weight, based on the non-volatile components of the coating agent.

[0058] Furthermore, the coating agent according to the invention contains at least one conventional and known paint additive in effective amounts, i.e. in amounts of up to 30% by weight, preferably up to 25% by weight, and in particular up to 20% by weight, in each case calculated for non-volatile coating agent ingredients.

[0059] Examples of suitable paint additives are:

- in particular a UV absorber;

in particular photostabilizers, such as HALS compounds, benzotriazoles or oxalanilides;

- radical acceptors;

- skidding accessories;

- polymerization inhibitors;

- anti-foaming agents;

active diluents, such as those generally known in the art and which are preferably inert towards the -Si (OR) 3 groups;

wetting agents such as siloxanes, fluorine-containing compounds, carboxylic acid half esters, phosphoric acid esters, polyacrylic acids and their copolymers or polyurethanes;

- adhesion promoters such as tricyclodecanedimethanol;

- leveling agents;

- film-forming auxiliaries such as cellulose derivatives;

- fillers, such as, for example, nanoparticles based on silicon dioxide, alumina or zirconia; supplementary information can be found in Rompp Lexikon "Lacke und Druckfarben", Georg Thieme Verlag Stuttgart, 1998, pages 250 252;

- additives regulating rheological properties, such as additives known from WO 94/22968, EP-A-0 276 501, EP-A-0 249 201 or WO 97/12945; cross-linked polymer microparticles as disclosed e.g. in EP-A-0 008 127; layered inorganic silicates such as magnesium aluminum silicate, layered sodium magnesium silicate and layered sodium magnesium fluoro lithium silicate of the montmorillonite type; silicas, such as Aerosile, or synthetic polymers with ionic groups and / or associative groups, such as polyvinyl alcohol, poly (meth) acrylamide, poly (meth) acrylic acid, polyvinylpyrrolidone, styrene-maleic anhydride copolymers or ethylene-maleic anhydride and their derivatives or hydrophobically modified ethoxylated urethanes or polyacrylates;

- and / or flame retardants.

[0060] In another embodiment of the invention, the coating agent according to the invention may contain still other pigments and / or fillers and can be used to produce pigmented topcoats. The pigments and / or fillers used for this purpose are known to the skilled person.

[0061] Since the coatings according to the invention made from the coating agents according to the invention also have excellent adhesion to already cured electrophoretically applied varnish coatings, fill varnish coatings, basic varnish coatings or typical and known colorless varnish coatings, In addition to the standard car body (OEM) application, they are also perfect for refinishing or modular scratches on already painted car bodies.

The coating according to the invention can be carried out by all conventional application methods, such as e.g. spraying, squeegee, brushing, pouring, dipping, impregnating, spraying or roller coating. The coated substrate can be at rest while the device or coating system is in motion. Alternatively, the coated substrate may also move, in particular a roll, the coating installation being stationary relative to the substrate or moving in a suitable manner.

[0063] Preferably, spray application methods are used, such as, for example, compressed air spraying, hydrodynamic spraying, high speed spraying, electrostatic spraying (ESTA), optionally in combination with hot lacquering, for example hot lacquering with hot air.

[0064] The curing of the coating agents applied according to the invention may take place after a certain rest time. The resting time is used, for example, to dissolve and degas the varnish layers or volatiles such as solvents to volatilize. The resting time can be aided and / or shortened by applying a higher temperature and / or by reducing the humidity, provided that there is no damage or change in the coating layers, for example premature total crosslinking.

[0065] The thermal curing of the coating agent is not particularly special, but it is carried out according to conventional and known methods, such as heating in a forced-air oven or irradiation with IR lamps. Thermal curing can also take place gradually. Near-infrared (NIR) curing is another preferred method of curing.

[0066] Thermal curing preferably takes place at a temperature of 30 to 200 ° C, particularly preferably 40 to 190 ° C, especially 50 to 180 ° C, during 1 min to 10 h, particularly preferably 2 min to 5 h and especially 3 min up to 3 h, while for the temperature used for car refinishing, which is preferably 30 to 90 ° C, a longer curing time can also be used.

[0067] The coating agents according to the invention provide new hardened coatings, in particular varnish coatings, especially colorless varnish coatings, shaped elements, especially optical shaped elements and self-supporting films, which are very scratch resistant and in particular resistant to chemicals and weathering. . In particular, it is possible to produce the coatings according to the invention and the varnish coatings, especially colorless varnish coatings, even with a layer thickness> 40 μm, without stress cracks.

[0068] The coating compositions according to the invention are therefore ideally suited for decorative, protective and / or giving the desired effect, highly scratch-resistant coatings and varnish coatings for vehicle bodies (in particular motor vehicles such as motorcycles, buses, trucks or passenger cars) or parts thereof; buildings inside and outside; furniture, windows and doors; plastic parts, in particular CDs and windows; small industrial parts, coils, tanks and packaging; household appliances; foil; optical, electrotechnical and mechanical construction elements and empty glass fittings and articles of everyday use.

[0069] In particular, the coating agents and varnish coatings according to the invention, especially the colorless varnish coating, are used in the technologically and aesthetically demanding field of serial car painting (OEM) and car refinishing. Particularly preferably, the coating compositions of the present invention are used in multi-stage coating processes, particularly those in which a pigmented basecoat layer is first applied to an optionally pre-coated substrate, followed by the coating agent layer according to the invention.

[0070] The present invention therefore also relates to a multistage coating process in which a pigmented base coat layer is applied to an optionally pre-coated substrate followed by a coating layer based on an aprotic solvent containing at least one compound (A) containing hydroxyl groups and at least one compound (B) containing isocyanate groups, characterized in that that one or more components of the coating agent applied to the base coat layer contain as additional functional components from 2.5 to 97.5 mol%, based on the total structural units (I) and (II), of at least one structural unit of formula (AND)

-N (X-SiR''x (OR ') 3-x) n (X'-SiR''y (OR') 3-y) m (I) in which R ', X, X', R ' ', n, m, m + n and x and y = 0 have the meanings given above, and from 2.5 to 97.5 mol%, calculated on the total of structural units (I) and (II), of at least one structural unit with formula (II),

-Z- (X-SiR''x (OR ') 3-x) (II) in which Z, R, R', X, R '' and x have the meanings given above.

[0071] Both water-soluble basecoats and basecoats based on organic solvents can be used. Suitable basecoats are described, for example, in EP-A-0 692 007 and the documents cited therein in column 3, line 50 and following lines. Preferably, the applied basecoat is first dried, i.e. at least part of the organic solvent or water is removed from the basecoat film in the evaporation phase. Drying preferably takes place at temperatures from room temperature to 80 ° C. After drying, the coating agent according to the invention is applied. Then, the two-layer varnish coat is fired preferably under the conditions used for serial painting of cars, at a temperature of 30 to 200 ° C, particularly preferably 40 to 190 ° C, especially 50 to 180 ° C, during 1 min to 10 h, particularly preferably 2 min to 5 h, especially 3 min to 3 h, where at the temperature used for car refinishing, which is preferably between 30 and 90 ° C, a longer curing time can also be used.

[0072] Coatings made of the coating agents according to the invention are characterized above all by particularly high resistance to chemicals and atmospheric agents as well as particularly high resistance to washing in car washes and scratch resistance, especially by a perfect combination of scratch resistance and resistance to atmospheric factors and radiation UV in the wet-dry cycle.

[0073] In another preferred embodiment of the invention, the coating agent of the invention is used as a transparent clearcoat for coating plastic substrates, in particular transparent plastic substrates. In this case, the coating agents contain UV absorbers, the amount and type of which are also adapted to effectively protect the plastic substrate from UV. Also in this case, the coating agents are characterized by a perfect combination of scratch resistance and resistance to weather conditions and UV radiation in the wet-dry cycle. Plastic substrates thus coated are preferably used as a material for replacing glass components in a car structure, the plastic substrates preferably made of polymethyl methacrylate or polycarbonate.

Examples

Preparation of component B according to the invention

Production example of VB1 - production of partially silanized polyisocyanate (HDI from 100 mole% IIa: conversion degree c = 30 mole%) (comparative example) [0074] In a three-necked flask equipped with a reflux condenser and a thermometer, a charge of 57.3 parts by weight was prepared. trimerized hexamethylene diisocyanate (HDI) (Basonat HI 100 from BASF AG) and 88.0 parts by weight of solvent naphtha. 21.8 parts by weight of N- [3- (trimethoxysilyl) propyl] butylamine (IIa) (Dynasilan® 1189 from Degussa) are dosed under cooling under a nitrogen reflux condenser and under stirring so as not to exceed 50 to 60 ° C . After completion of dosing, the reaction temperature was kept at 50 to 60 ° C until the weight fraction of isocyanates, determined by titration, was the theoretically calculated level of 70 mol%.

[0075] The partially silanized polyisocyanate solution had a solids content of 47.1 wt.

Production Example B1 - Preparation of partially silanized polyisocyanate (HDI with 70 mole% IIa and 30 mole% Ia: Conversion rate c = 30 mole%) [0076] In a three-necked flask equipped with a reflux condenser and thermometer, a charge of 57.3 parts was prepared. by weight of trimerized hexamethylene diisocyanate (HDI) (Basonat HI 100 from BASF AG) and 69.7 parts by weight of solvent naphtha. A mixture of 14.8 parts by weight of N- [3- (trimethoxysilyl) propyl] butylamine (Dynasilan® 1189 from Degussa) (IIa) and 9.2 parts by weight bis [ 3- (trimethoxysilyl) propyl] amine (Ia) (Dynasilan® 1124 from Degussa) so as not to exceed 50 to 60 ° C. After completion of dosing, the reaction temperature was kept at 50 to 60 ° C until the weight fraction of isocyanates, determined by titration, was the theoretically calculated level of 70 mol%.

[0077] The partially silanized polyisocyanate solution had a solids content of 53.9 wt.

Production Example B2 - Preparation of partially silanized polyisocyanate (HDI with 30 mole% IIa and 70 mole% Ia: Conversion rate c = 30 mole%) [0078] In a three-necked flask equipped with a reflux condenser and thermometer, a charge of 57.3 parts was prepared. by weight of trimerized hexamethylene diisocyanate (HDI) (Basonat HI 100 from BASF AG) and 69.7 parts by weight of solvent naphtha. A mixture of 6.4 parts by weight of N- [3- (trimethoxysilyl) propyl] butylamine (Dynasilan® 1189 from Degussa) (IIa) and 21.5 parts by weight bis [ 3- (trimethoxysilyl) propyl] amine (Ia) (Dynasilan® 1124 from Degussa) so as not to exceed a temperature of 50 to 60 ° C. After completion of dosing, the reaction temperature was kept at 50 to 60 ° C until the weight fraction of isocyanates, determined by titration, was the theoretically calculated level of 70 mol%.

[0079] The partially silanized polyisocyanate solution had a solids content of 55.0 wt.

Production Example VB2 - Preparation of partially silanized polyisocyanate (HDI with 100 mol% Ia: Conversion rate c = 30 mol%) (comparative example) [0080] A batch of 57.3 parts by weight was prepared in a three-necked flask equipped with a reflux condenser and thermometer. trimerized hexamethylene diisocyanate (HDI) (Basonat HI 100 from BASF AG) and 88.0 parts by weight of solvent naphtha. 30.7 parts by weight of bis- [3- (trimethoxysilyl) propyl] amine (Ia) (Dynasilan® 1124 from Degussa) are dosed in a reflux condenser, under nitrogen and during stirring, so as not to exceed 50 to 60 ° C . After completion of dosing, the reaction temperature was kept at 50 to 60 ° C until the weight fraction of isocyanates, determined by titration, was the theoretically calculated level of 70 mol%.

[0081] The partially silanized polyisocyanate solution had a solids content of 63.0 wt.

Production Example VB3 - Preparation of partially silanized polyisocyanate (HDI from 100 mole% IIa: Conversion rate c = 70 mole%) (comparative example) [0082] A batch of 57.3 parts by weight was prepared in a three-necked flask equipped with a reflux condenser and thermometer. trimerized hexamethylene diisocyanate (HDI) (Basonat HI 100 from BASF AG) and 88.0 parts by weight of solvent naphtha. When cooling under reflux, under nitrogen and during stirring, 49.4 parts by weight of N- [3- (trimethoxysilyl) propyl] butylamine (IIa) (Dynasilan® 1189 from Degussa) are metered in so as not to exceed a temperature of 50 to 60 ° C . After completion of dosing, the reaction temperature was kept at 50 to 60 ° C until the weight fraction of isocyanates, determined by titration, was the theoretically calculated 30 mol%.

[0083] The partially silanized polyisocyanate solution had a solids content of 54.8 wt.

Production example B3 - production of partially silanized polyisocyanate (HDI with 70 mole% IIa and 30 mole% Ia: conversion ratio c = 70 mole%) [0084] In a three-necked flask equipped with a reflux condenser and thermometer, a charge of 57.3 parts was prepared. by weight of trimerized hexamethylene diisocyanate (HDI) (Basonat HI 100 from BASF AG) and 69.7 parts by weight of solvent naphtha. A mixture of 34.6 parts by weight of N- [3- (trimethoxysilyl) propyl] butylamine (Dynasilan® 1189 from Degussa) (IIa) and 21.5 parts by weight bis [ 3- (trimethoxysilyl) propyl] amine (Ia) (Dynasilan® 1124 from Degussa) so as not to exceed 50 to 60 ° C. After completion of dosing, the reaction temperature was kept at 50 to 60 ° C until the weight fraction of isocyanates, determined by titration, was the theoretically calculated 30 mol%.

[0085] The partially silanized polyisocyanate solution had a solids content of 61.9 wt.

Production example B4 - production of partially silanized polyisocyanate (HDI from 30 mole% IIa and 70 mole% Ia: conversion ratio c = 70 mole%) [0086] In a three-necked flask equipped with a reflux condenser and thermometer, a charge of 57.3 parts was prepared. by weight of trimerized hexamethylene diisocyanate (HDI) (Basonat HI 100 from BASF AG) and 88.0 parts by weight of solvent naphtha. A mixture of 14.8 parts by weight of N- [3- (trimethoxysilyl) propyl] butylamine (Dynasilan® 1189 from Degussa) (IIa) and 50.2 parts by weight bis [ 3- (trimethoxysilyl) propyl] amine (Ia) (Dynasilan® 1124 from Degussa) so as not to exceed a temperature of 50 to 60 ° C. After completion of dosing, the reaction temperature was kept at 50 to 60 ° C until the weight fraction of isocyanates, determined by titration, was the theoretically calculated level of 70 mol%.

[0087] The partially silanized polyisocyanate solution had a solids content of 58.2 wt.

Preparation of polyacrylate polyol A [0088] In a steel tank equipped with monomer feed, initiator feed and thermometer, oil heating and reflux condenser, heated to 140 ° C 29.08 parts by weight of a commercial aromatic solvent mixture (Solventnaphtha® from DHC Solvent Chemie GmbH). Then, while stirring, a mixture of a1 with 3.39 parts by weight of solvent naphtha and 2.24 parts by weight of tert-butylperoxy-2-ethylhexanoate was added at such a rate that the addition of mixture a1 was completed after 6.75 hours. 15 minutes after the start of adding the mixture a1, the mixture a2 consisting of 4.97 parts by weight styrene, 16.91 parts by weight tert-butyl acrylate, 19.89 parts by weight 2-hydroxypropyl methacrylate, 7.45 parts by weight n-butyl methacrylate was added and 0.58 parts by weight of acrylic acid at such a rate that the addition of the a2 mixture was completed after 6 h. After the a1 mixture was added, the reaction mixture was held for another 2 h at 140 ° C and then cooled below 100 ° C. The reaction mixture was then further diluted with a3 mixture from 3.70 parts by weight of 1-methoxy-2-propyl acetate, 3.06 parts by weight of butyl glycol acetate and

6.36 parts by weight of 98/100 butyl acetate.

[0089] The resulting polyacrylate polyol A solution has a solids content of 52.4% (1h, 130 ° C, forced air oven), viscosity 3.6 dPas (cone-plate viscometer, according to ICI, 23 ° C), hydroxyl number 155 mg KOH / g acid number 10-13 mg KOH / g.

Formulation of the coating agent according to the invention and comparative examples [0090] The coating agent according to the invention and comparative samples were formulated as follows:

[0091] Component 1, containing component A (polyol) and typical commercial additives and catalyst and solvent, were combined shortly before application with component 2, containing component B (modified polyisocyanate) and mixed until a homogeneous mixture was formed. The application was carried out pneumatically under a pressure of 2.5 bar in three spraying stages. The coating was then deaerated for 5 minutes at room temperature and then fired for 22 minutes at 140 ° C.

[0092] Table 1 shows all coatings, taking into account the content of ingredients:

Table 1 - Formulation of the coating agent according to the invention and comparative examples

<td>Component B according to an example</td><td>VB1</td><td>B1</td><td>B2</td><td>VB2</td><td>VB3</td><td>B3</td><td>B4</td>

<td>Parts by weight of polyacrylate polyol A according to an example</td><td> 45,0</td><td> 45,0</td><td> 45,0</td><td> 45,0</td><td> 45,0</td><td> 45,0</td><td> 45,0</td>

<td>Parts by weight of component B</td><td> 52,0</td><td> 47,2</td><td> 48,3</td><td> 43,7</td><td> 144,9</td><td> 133,0</td><td> 153,0</td>

<td>Parts by weight of the catalyst¹(Nacure 4167, King Industries) 25% non-volatile parts)</td><td> 2,1</td><td> 2,2</td><td> 2,3</td><td> 2,4</td><td> 6,9</td><td> 7,2</td><td> 7,8</td>

<td>BYK 301 weight parts (leveling agent, Taurus Chemie)</td><td> 0,2</td><td> 0,2</td><td> 0,2</td><td> 0,2</td><td> 0,2</td><td> 0,2</td><td> 0,2</td>

<td>Weighing parts Tinuvin 384.2 (Ciba)</td><td> 0,9</td><td> 0,9</td><td> 0,9</td><td> 0,9</td><td> 0,9</td><td> 0,9</td><td> 0,9</td>

<td>Weighing parts Tinuvin 292 (Ciba)</td><td> 0,8</td><td> 0,8</td><td> 0,8</td><td> 0,8</td><td> 0,8</td><td> 0,8</td><td> 0,8</td>

<td>Weighing parts by solvent (DHC Solvent Chemie GmbH)</td><td> 20,0</td><td> 20,0</td><td> 20,0</td><td> 20,0</td><td> 20,0</td><td> 20,0</td><td> 20,0</td>

<td>Equivalent ratio of free isocyanate groups in</td><td> 1,00:</td><td> 1,00:</td><td> 1,00:</td><td> 1,00:</td><td> 1,00:</td><td> 1,00:</td><td> 1,00:</td>

<td>component B to the hydroxyl groups in polyacrylate polyol A</td><td> 1,00</td><td> 1,00</td><td> 1,00</td><td> 1,00</td><td> 1,00</td><td> 1,00</td><td> 1,00</td>

<td colspan="8">¹) a catalyst based on an aminoblocked half phosphoric acid ester</td>

[0093] The scratch resistance of the surfaces of the resulting coatings was tested by means of a Crockmeter tart meter (based on EN ISO 105-X12 with 10 double strokes and 9N contact force, using 9 μm abrasive paper (3M 281 Q wetordry^™production^™), followed by the determination of residual gloss at 20 ° C using a commercially available gloss measuring device, and by means of a hammer test (10 or 100 double strokes with steel wool (RAKSO^®00 (Fein)) with a 1 kg weight attached, which is carried out using a hammer. The residual gloss is then again determined at 20 ° C using a commercially available gloss measuring device. Weather resistance was tested using the CAM180 test (according to DIN EN ISO 11341 February 98 and DIN EN ISO 4892-2 November 00). The results are given in Table 2.

Table 2 - Properties of the clearcoat layers produced from the coating agents of the invention

<td>Coating agent with component B according to the example</td><td>VB1</td><td>B1</td><td>B2</td><td>VB2</td><td>VB3</td><td>B3</td><td>B4</td>

<td>Test with Crockmeter (residual gloss in%)</td><td> 41</td><td> 53</td><td> 58</td><td> 63</td><td> 75</td><td> 88</td><td> 95</td>

<td>10 DH hammer test (residual gloss in%)</td><td> 38</td><td> 49</td><td> 60</td><td> 64</td><td> 79</td><td> 88</td><td> 93</td>

<td>100 DH hammer test (residual gloss in%)</td><td> 0</td><td> 1</td><td> 18</td><td> 28</td><td> 65</td><td> 81</td><td> 92</td>

<td>CAM 180 (h) test to appear cracks</td><td> 5500</td><td> 5250</td><td> 5000</td><td> 4500</td><td> 5250</td><td> 5000</td><td> 4000</td>

[0094] The table shows the coating agents according to the invention with components B1, B2,

B3 and B4, compared to coating agents containing isocyanurate adduct

B derived from the reaction of HDI isocyanurate, below briefly HDI, and only component Ia (comparative example VB2) or IIA (comparative examples VB1 and VB3).

[0095] With an HDI isocyanate conversion of 30 mol%, VB1 (containing structural units II) compared to VB2 (containing structural units I) shows a significantly longer time in the CAM 180 test until cracks appear. Accordingly, with an HDI isocyanate conversion of 70 mole%, Example VB3 (containing only structural units II) compared to B4 (containing 70 mole% of structural units I) shows a significantly longer time in the CAM 180 test until cracks appear. In contrast, scratch resistance is maintained: with a conversion of HDI isocyanate groups of 30 mol%, VB1 (containing structural units II) compared to VB2 (containing structural units I) exhibits clearly lower scratch resistance in various scratch tests. Correspondingly, with a HDI isocyanate conversion of 70 mol%, Example VB3 (containing only structural units II) compared to B4 (containing 70 mol% of structural units I) shows clearly lower scratch resistance in various scratch tests. Because the relative proportion of structures I is responsible for scratch resistance, and the proportion of structures II is responsible for weather resistance, therefore, by carefully mixing both siloxanoamines Ia or IIa, an accurate adjustment of the duration of weathering with the scratch resistance can be achieved. For example, VB1 and VB2 can be opposed to B1 and B2 in a group with 30 mol% conversion of isocyanate functional groups. VB1 achieves a high value of resistance to weather conditions, however, the scratch resistance is moderate. VB2 has a good scratch resistance value, but is weaker in terms of weathering resistance. Both examples B1 and B2 have better scratch resistance compared to VB1 and better weather resistance compared to VB2.

[0096] The same applies to VB3 against B3 and B4 in a group with a 70% molar degree of isocyanate conversion, but here an even stronger effect is observed on both scratch resistance and weather resistance due to the high relative proportion of siloxane functional groups . It is also seen that with a large degree of conversion of isocyanate functional groups, the relative proportion of structure II significantly affects the resistance to weathering than structure I against scratching, as can easily be seen by comparing these values ​​in B3 and B4. In general, the scratch resistance value correlates with the degree of conversion of isocyanate groups with compounds I and II, whereby a large degree of isocyanate group conversion is required to achieve very high scratch resistance.

[0097] In addition, it is important that the coatings obtained have good scratch resistance immediately after curing for 20 min at 140 ° C and therefore, immediately after thermal curing, they can be handled without problems.