BR112015013720B1 - TWO COMPONENT WATER PRIMER COMPOSITION, METHOD TO PRODUCE A COATING AND COATED SUBSTRATE - Google Patents

Abstract

aqueous two-component primer composition, method for producing a coating and coated substrate. the present invention relates to a two-component aqueous primer composition comprising (1) a paint-based component comprising (a) at least one polyurethane resin having an oh number from 5 to 60 mg kohig, (b) zinc phosphate, (c) at least one pigment, and (2) a curing component comprising (d1) at least one polyisocyanate which is an isocyanurate based on hexamethylene diisocyanate, (d2) at least one polyisocyanate which is a polyether modified isocyanurate based on isophorone diisocyanate, where the stoichiometric ratio of isocyanate groups in the curing component to the complementary hydroxyl groups in the paint base component is greater than 2. the present invention additionally relates to a method for producing a coating on a metallic substrate, applying the primer composition of the invention directly to a substrate. moreover, the present invention relates to a substrate coated by the indicated method.

Description

TWO COMPONENT WATER PRIMER COMPOSITION, METHOD TO PRODUCE A COATING AND COATED SUBSTRATE

[0001] The present invention relates to a 2-component aqueous primer composition comprising a polyurethane resin, a filler component and two different polyisocyanates. The present invention further relates to a method for producing coatings using the primer composition, where the primer composition is applied directly to a substrate. Coatings have excellent adhesion and are therefore exceptionally suitable, for example, to increase the corrosion protection afforded to metal substrates, especially as part of automotive refinishing.

TECHNICAL STATUS

[0002] In the context of automotive finishing, a wide variety of different substrates, and more particularly metallic substrates, are generally coated with various coatings, to meet the various technological performance requirements that are imposed on coated substrates, such as corrosion resistance, for example. The coatings involved are generally multi-coating systems comprising - from the metallic substrate - a conversion coating (phosphate coating, for example) and also an electrocoating, a leveling primer coating, a matte base and a transparent coating. A less complex and therefore more economical coating system would be an advantage in this context. In this case, of course, it will still be necessary for the technological performance properties of the global coating to meet the demanding requirements of the automotive industry.

[0003] Attempts are being made, for example, to replace the corrosion protection electrocoating and the leveling primer coating with a single coating that unites the properties of the two coatings mentioned above. In this context, a particular problem is to maintain adequate corrosion protection and achieve acceptable adhesion and, therefore, resistance to water and moisture, by the general coating. If attempts are made not only to bond electrocoating and leveling primer coating, but also to function without the conversion coating, in order to make the coating and coating process more economical and faster to implement, the problems in terms of strength corrosion are further intensified. For example, the adhesion of substitute coatings (primer coatings) applied directly to the metallic substrate (direct-to-metal) is often not sufficient to guarantee the maintenance of the coating even under long-term weathering effects, more particularly humidity effects .

[0004] The problems addressed are of relevance, not only in the context of the original finish (OEM) of substrates - such as, for example, substrates which are painted as part of automotive OEM finish. Particular attention should be paid to these problems in the refinishing segment, more particularly automotive refinishing. On the one hand, in this particular segment, a reduction in the number of individual coatings to be applied is an advantage, allowing the overcoating operation to be conducted more quickly and economically. On the other hand, especially with repainting, where regions with an original finish damaged locally are surrounded by intact areas of the original finish, the adhesion achieved is often insufficient. This is especially the case if any residues from the original finish, together with the corrosion products that are generally already developed, are to be removed from the damaged site by cleaning and abrasion, and the substrate surface is exposed as a result. Adhesion problems no less arise from the different interfaces. First, here, there is the interface between repainting and the exposed substrate.
In addition, the newly applied finish must also adhere to the corresponding interfaces and boundary edges in the region between the damaged, clean, and abraded areas and also to the regions with the original intact finish that surround those areas. In all of these interfaces, a single coating composition must ensure adequate adhesion. The provision of a direct-to-metal primer composition which can be used in overcoating and which provides adequate corrosion protection is therefore an even greater challenge.

[0005] Coating compositions with which attempts are made to combat stated problems, especially with regard to poor adhesion and poor corrosion protection in connection with the described direct-to-metal primer coatings, are described in the application US2006 / 0047085, for example. The coating compositions described therein have acceptable corrosion resistance and wear resistance, but contain relatively large amounts of organic solvents.

[0006] Today, however, specific limits on emissions of volatile organic substances, especially solvents, are established by law for the operation of industrial paint plants. In addition, compliance with legal stipulations must be properly demonstrated (cf., for example, the 31st German Airborne Pollutants Ordinance, as well as the corresponding VOC Ordinances VOC and EU ordinances). Particularly, as part of what is called a simplified reduction plan, developed specifically for paint plants in the smaller segment (automotive refinishing, for example), it can be assumed that legal approval for the operation of these plants in the future would be achievable through the use of coating compositions having a VOC of less than 250 g / l. For coating compositions in the form in which they were formulated ready for use, VOC is defined as follows: VOC (g / l) = (mass of volatile compounds (g) - masses of water (g)) / (volume of material of coating (l) - volume of water (l)). Volatile compounds here are those compounds which at processing temperature, more particularly 20 ° C, exceed a vapor pressure of 10 Pascals. They include, in particular, the commonly known organic solvents, examples being the organic solvents specified below and also water. Coating compositions which, in the ready to process state, have a low VOC level of this type, in general, have only a small amount of organic solvents and, in addition, a high fraction of water compared to organic solvents.

OBJECTS OF THE PRESENT INVENTION

[0007] Therefore, it is advantageous - and therefore an object of the present invention - to provide an aqueous primer composition which no longer has the disadvantages of the prior art, but which instead, as part of the substrate finish metallic, can be applied directly to the substrate and which, as a coating, has excellent adhesion and also resistance to corrosion, especially under weathering effects such as moisture. The coating produced with the primer composition must be directly re-coatable with conventional matte-based materials, of the type used more particularly in the automotive industry, and therefore a coating system must be possible, ie substantially less complex in comparison with conventional automotive finish. Despite this, the demanding requirements imposed on multi-coated automotive finishes and particularly good protection against corrosion, must be fully satisfied. In addition, the primer composition must be watery and include as small a fraction as possible of volatile organic substances, such as solvents, in order to satisfy the growing legal requirements in relation to ecological awareness. More particularly, the primer composition must be capable of being produced in such a way that it falls below the 250 g / l VOC limit in its service state. The primer composition and the method for direct coating of metal substrates using the particular primer composition should be amenable to use in automotive refinishing.

• (A) pelo menos uma resina de poliuretano tendo um número de OH de 5 a 60 mg KOH/g,
• (B) fosfato de zinco,
• (C) pelo menos um pigmento,

e
(2) um componente de cura compreendendo:
(D1) pelo menos um poliisocianato o qual é um isocianurato baseado em diisocianato de hexametileno,
(D2) pelo menos um poliisocianato o qual é um isocianurato modificado por poliéter com base em diisocianato de isoforona,
onde a razão estequiométrica de grupos isocianatos no componente de cura para os grupos hidroxil complementares no componente de base de pintura é maior que 2.[0008] It was possible to reach these objects by means of a new two-component aqueous primer composition comprising:
(1) a base paint component comprising

• (A) at least one polyurethane resin having an OH number of 5 to 60 mg KOH / g,
• (B) zinc phosphate,
• (C) at least one pigment,

and
(2) a healing component comprising:
(D1) at least one polyisocyanate which is an isocyanurate based on hexamethylene diisocyanate,
(D2) at least one polyisocyanate which is a polyether modified isocyanurate based on isophorone diisocyanate,
where the stoichiometric ratio of isocyanate groups in the curing component to the complementary hydroxyl groups in the base paint component is greater than 2.

[0009] The new primer composition is referred to below as the primer composition of the invention. It can be applied directly to various metallic substrates, and the coatings produced in this way have excellent adhesion and resistance to corrosion. Accordingly, the present invention provides not only the primer composition, but also a method for producing a coating on a substrate, applying the primer composition of the invention directly to the substrate. Where the primer composition of the invention, or a coating produced therefrom arising directly on a substrate, is part of a multi-coating coating system, there is no need for a conversion coating or a leveling primer coating in this multi-coating coating system , with no consequent deleterious effect on performance properties. On the contrary: these properties, especially the adhesion of the general coating to be the substrate and the corrosion protection, are excellent. It has been surprisingly possible to achieve these excellent properties despite the fact that the primer composition is aqueous and is easily produced such that the VOC is below the VOC limit of 250 g / l. Success is achieved, therefore, in the exceptional combination of performance properties with an environmentally valuable profile.

DESCRIPTION MEASUREMENT METHODS

[0010] For the purposes of the invention, the hydroxyl number (OH number) indicates the amount of potassium hydroxide in mg, which is equivalent to the molar amount of acetic acid bound in the acetylation of one gram of the constituent in question. The hydroxyl number in the context of the present invention is determined experimentally by titration in accordance with DIN 53240-2 (determination of the hydroxyl value - part 2: Method with catalyst) unless otherwise specified.

[0011] For the purposes of the invention, the acid number indicates the amount of potassium hydroxide in mg, which is necessary to neutralize 1 g of the constituent in question. For the purposes of the present invention, the acid number is determined experimentally by titration in accordance with DIN EN ISO 2114 unless otherwise stated.

[0012] For the purposes of the present invention, the average mass (Mw) and the average number molecular weights (Mn) are determined by means of gel permeation chromatography at 40 ° C, using a high performance liquid chromatography pump. and a refractive index detector. The eluent used was tetrahydrofuran, with an elution rate of 1 ml / min. Calibration is performed using a polystyrene standard.

[0013] The isocyanate content in the context of the present invention is determined in accordance with DIN EN ISO 11909, by reacting the respective sample with excess dibutylamix and excess return titration with hydrochloric acid against bromophenol blue.

[0014] For the purposes of the present invention, the content of non-volatile compounds (nvc, solids) was determined under conditions selected to be constant in each case, unless otherwise specified. The content of non-volatile compounds is determined by heating an amount of 2 g of the constituent in question, such as a dispersion of a polymer or resin in appropriate non-volatile solvents, for example, at 125 ° C for 2 hours, cooling to 20 ° C. ° C and then weighing the amount of waste (see also ISO 3251). The content of non-volatile components of corresponding dispersions of polymers or resins which are used in the primer composition of the invention is determined, for example, in order, thus, to be able to adjust and determine, for example, the weight fraction of the respective constituent in a mixture of two or more constituents, or of the primer composition as a whole.

PRIMER COMPOSITION

[0015] The primer composition of the invention is a multicomponent, more particularly a two-component (2K) coating material composition.

[0016] This means that, in the context of the present invention, component (1) as described below (paint base component) and component (2) as described below (curing component) are prepared and stored separately from each other and are not combined until just before application. The processing life (in other words, the time in which the primer composition of the invention can be processed at room temperature (15 to 25 ° C, more particularly 20 ° C) without corresponding cross-linking reactions, at room temperature, for example , causing an increase in viscosity that the application is no longer possible) of course depends on the constituents used and more particularly on the polyurethane (A) and polyisocyanate (C1) and (C2) resins, which are described later below. The processing life of the primer composition is, however, more particularly at least 5 minutes to 60 minutes, preferably at least 15 minutes to 60 minutes.

[0017] The primer composition of the particular invention can be thermally curable. In the context of the present invention, "thermally curable" or the term "thermal cure" denotes the crosslinking of a paint coating (formation of a coating film) that occurs as a result of the chemical reaction of certain functional groups, the energetic activation of this reaction chemical, being possible through thermal energy. It may be the case here that complementary, different functional groups react with each other, and / or that film formation derives from the reaction of self-reactive groups, in other words functional groups which react with groups of the same type. Examples of suitable complementary reactive functional groups and self-reactive functional groups are known from German patent application DE 199 30 665 A1, page 7, line 28, page 9, line 24, for example. Particularly notable as complementary functional groups are hydroxyl groups and isocyanate groups.

[0018] This crosslinking can be self-crosslinking and / or external crosslinking. Where, for example, complementary reactive functional groups are already present in an organic polymer which is used as a binder, the form of crosslinking is self-crosslinking. External crosslinking is present, for example, if an organic polymer containing specific functional groups reacts with a different crosslinking agent, possibly in the same form as polymers, the crosslinking agent in this case containing reactive functional groups, which are complementary to reactive functional groups present in the used organic polymer. It is also possible for an organic polymer binder to have not only self-crosslinking, but also functional crosslinking groups externally and then be combined with crosslinking agents.

[0019] Since it comprises the polyisocyanates (C1) and (C2) and a hydroxy-functional polyurethane resin (A) as described later below, the primer composition of the invention is at least partially externally cross-linked and therefore at least partially thermally curable. In general, however, after application to a substrate, the primer composition also undergoes partial physical curing, or is partially physically curable. In the context of the present invention, "physically curable" or the term "physical curing" the term denotes the formation of a film by the loss of solvent from polymer solutions or polymer dispersions. Again, it is not impossible for additional polymers, such as polymers self-crosslinking, for example, may be present, and hence also that the primer composition can be partly cured, or curable, thermally with self-crosslinking.

COMPONENT CONSTITUENTS (1) (PAINT BASE COMPONENT) POLYURETHANE RESIN (A)

[0020] The first essential constituent of the base paint component of the coating composition of the invention is at least one polyurethane resin (A), as defined below.

[0021] Polyurethane resins, their preparation and use in coating compositions are known to the skilled person. They are usually prepared by the reaction of polyisocyanates known to you with polyols that are also known, it is also possible in each case, of course, to use monofunctional compounds, especially mono-alcohols. In addition, polyurethane resins can be hydrophilically stabilized ionically and / or non-ionically.

• - Patente Européia EP 0521 928 B1, página 2, linha 57, página 8, linha 16,
• -Pedido de patente alemão DE 199 14 055 A1, página 2, linha 24, página 4, linha 16
• -Pedido de patente europeia EP 0 228 003 A1, página 3, linha 24, página 5, linha 40,
• -Pedido de patente europeia EP 0 634 431 A1, página 3, linha 38, página 8, linha 9, ou
• -Pedido de patente internacional WO 92/15405, página 2, linha 35, a página 10, linha 32, ou outra
• -Pedido de patente alemão DE 3545618 A1, coluna 6, linha 39, a coluna 9, linha 66.

[0022] Polyurethane resins, their preparation and use in coating materials are described for example in

• - European Patent EP 0521 928 B1, page 2, line 57, page 8, line 16,
• - German patent application DE 199 14 055 A1, page 2, line 24, page 4, line 16
• -European patent application EP 0 228 003 A1, page 3, line 24, page 5, line 40,
• -European patent application EP 0 634 431 A1, page 3, line 38, page 8, line 9, or
• -International patent application WO 92/15405, page 2, line 35, page 10, line 32, or other
• - German patent application DE 3545618 A1, column 6, line 39, column 9, line 66.

[0023] Polyurethane resin (A) is prepared using, for example, the organic polyisocyanates known to you by the skilled person, that is, the aliphatic, cycloaliphatic, cycloaliphatic-aliphatic, aromatic, aromatic and / or cycloaliphatic aliphatics known aromatics.

[0024] Examples of suitable diisocyanates are isophorone diisocyanate, 5-isocyanato-1- (2-isocyanatoet-1-yl) -1,3,3-trimethylcyclohexane, 5-isocyanate-1- (3-isocyanatoprop-1 -yl) -1,3,3-trimethylcyclo, 5-isocyanato- (4-isocyanatobut-1-yl) -1,3,3-trimethylcyclohexane, 1-isocyanato-2- (3-isocyanatoprop-1-yl ) cyclohexane, 1-isocyanate-2- (3-isocyanatoet-1-yl) cyclohexane, 1-isocyanate-2- (4-isocyanatobut-1-yl) cyclohexane, 1,2-diisocyanatocyclobutane, 1 , 3-diisocyanatocyclobutane, 1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-2,4'-diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, ethylene diisocyanate, trimethylhexane diisocyanate, heptamethylene diisocyanate, diisocyanates or derived from fatty acid dimers, of the type described in WO 97/49 such as, for example, 2-heptyl-3,4-bis (9-isocyanatononyl) -1-pentylcyclohexane, or 1,2-, 1, 4- or 1,3-bis (isocyanatomethyl) cyclohexane, 1, 2-, 1,4- or 1,3-bis (2-isocyanatoet-1-yl) cyclohexane, 1,3-bis (3-isocyanatoprop-1-yl) cyclohexane, 1,2-, 1 , 4- or 1,3-bis (4-isocyanatobut-1-yl) cyclohexane; tolylene diisocyanate, xylylene diisocyanate, bisphenylene, naphthylene diisocyanate or diphenylmethane diisocyanate. Examples of suitable polyisocyanates are also the isocyanurates of the diisocyanates described above.

[0025] Examples of suitable monoisocyanates, which can be used in the preparation of polyurethane resin (A) phenyl isocyanate, cyclohexyl isocyanate or stearyl isocyanate.

[0026] Polyols used for the preparation of polyurethane (A) resins are, for example, the saturated and unsaturated polyols of relatively high molecular weight and low molecular weight that are known to the skilled person, for example and also, optionally, mono-alcohols, in smaller quantities. Low molecular weight polyols used are more particularly monomeric diols and, in smaller amounts, monomeric triols for the purpose of introducing branches.

[0027] Examples of suitable diols are ethylene glycol, 1,2 or 1,3-propanediol, 1,2, 1,3 or 1,4-butanediol, 1,2-, 1,3-, 1,4 - or 1,5-Pentanedial, 1,2-, 1,3-, 1,4-, 1,5 - or 1,6-hexanediol, Neopentyl hydroxypivalate, Neopentyl glycol, diethylene glycol, 1,2-, 1,3 - or 1,4-cyclohexanediol, 1,2-, 1,3 - or cyclohexane-1,4-dimethanol, trimethyl pentanediol, ethylbutylpropanediol, or positionally isomeric diethyloctanediol.

[0028] Examples of suitable trols are trimethylolethane, trimethylolpropane or glycerol.

[0029] Examples of suitable mono-alcohols are ethanol, propanol, n-butanol, sec-butanol, tert-butanol, amyl alcohols, hexanes, fatty alcohols, allyl alcohol or phenol.

[0030] Examples of suitable polyols of relatively high molecular weight are saturated or olefinically unsaturated polyether polyols and / or polyester polyols, more particularly polyester polyols, examples being those having average molecular weights of 400 to 5000 g / mol. Polyester polyols can be prepared, for example, using said polyols of molecular weight and also using corresponding polycarboxylic acids.

[0031] Suitable polycarboxylic acids are the organic polycarboxylic acids that are known for themselves, these being, for example, aromatic, aliphatic acids and cycloaliphatic polycarboxylic acids.

[0032] Examples of suitable aliphatic polycarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pyelic acid, Suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, dimer or fatty acids maleic, fumaric acid or itaconic acid.

[0033] Examples of suitable cycloaliphatic polycarboxylic acids are 1,2-cyclobutanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, hexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1 , 4-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid, hydrophthalic acid or 4-methyltetrahydrophthalic acid.

[0034] Examples of suitable aromatic polycarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, or else halophthalic acids.

[0035] Of course it is also possible to use, for example, corresponding anhydrides of polycarboxylic acids, an example being hexahydrophthalic anhydride. Also, of course, it is possible to use monocarboxylic acids that are known for themselves, such as benzoic acid, tert-butylbenzoic acid, lauric acid, isononanoic acid, fatty acids from natural oils, or crotonic acid.

[0036] For the purpose of hydrophilic stabilization and / or to increase the dispersion capacity in aqueous medium, polyurethane resins, an example being polyurethane resin (A), generally comprise certain groups of modifications in an ionic and / or non-ionic manner , preferably ionic groups. More specifically, these groups are alternatively
- functional groups which can be converted into cations by neutralizing agents and / or quatenizing agents (potentially cationic groups), and / or cationic groups (cationic modification)
or
- functional groups which can be converted into anions by neutralizing agents (potentially anionic groups), and / or anionic groups (anionic modification),
and / or
- non-ionic hydrophilic groups (non-ionic modification).

[0037] As the skilled person is aware, functional groups for cationic modification are, for example, primary, secondary or tertiary amino acid groups, secondary sulfide groups and / or tertiary phosphine groups, more particularly tertiary amino acid groups and secondary sulfide groups (functional groups which can be converted to cations by neutralizing agents and / or quartenizing agents). Additionally notable are the cationic groups that are prepared with said functional groups using neutralizing agents and / or quartenizing agents that are known to the skilled person, such as primary, secondary, tertiary and / or quaternary ammonia groups, tertiary sulphonium groups and / or quaternary phosphonium groups, more particularly quaternary ammonia groups and tertiary sulphonium groups.

[0038] Examples of functional groups for anionic modification, as is known, groups of carboxylic, sulfonic and / or phosphonic acids, more particularly groups of carboxylic acid (functional groups which can be converted into anions by neutralizing agents) and also anions prepared from the above functional groups using neutralizing agents which are known to the skilled person, such as carboxylate, sulfonate and / or phosphonate groups, more particularly carboxylate groups.

[0039] Functional groups for non-ionic hydrophilic modification are preferably poly (oxyalkylene) groups, more particularly poly (oxyethylene) groups.

[0040] Hydrophilic modifications can be introduced in the polyurethane resin (A) using, for example, corresponding monomers, which contain the ionic groups (potentially). Non-ionic modifications are introduced, for example, through the incorporation of poly (ethylene) polymers, as side or terminal groups of the polyurethane molecules. Hydrophilic modifications are introduced, for example, by means of compounds which contain at least one group that is reactive to isocyanate groups, preferably at least one hydroxyl group. To introduce ionic modification it is possible to use monomers which, as well as the modifying groups contain at least two hydroxyl groups. It is also possible, for example, for the preferred carboxylic acids and / or carboxylate groups to be introduced at least partially by the polyester polyols mentioned above, which can be used as relatively high molecular weight polyols in the preparation of polyurethane resins (A) . To introduce nonionic modifications, it is preferable to use the poly (oxyalkylene) alkoxy alcohols and / or polyether diols that are known to the skilled person.

[0041] Polyurethane resin (A) is hydroxy-functional. This mainly means that in the reaction described above of the corresponding starting compounds, that is, the polyisocyanates and polyols, the selected specific starting compounds are reacted with each other in stoichiometries such that the polyurethane resin (A) still contains free hydroxyl groups. At the same time, however, it is also essential for the invention that the OH number of the polyurethane resin (A) is not too high. Only in this way are the advantageous effects of the invention achieved.

[0042] The polyurethane resin (A) has an OH number of 5 to 60 mg KOH / g, preferably 8 to 50 mg KOH / g, most preferably 10 to 40 mg KOH / g.

[0043] The polyurethane resin (A) preferably contains carboxylic acid and / or carboxylate groups for hydrophilic stabilization. Preferably it has an acid number of 5 to 80 mg KOH / g, more preferably 6 to 60 mg KOH / g, most preferably 10 to 40 mg KOH / g.

[0044] The polyurethane resin (A) preferably has an average molecular weight Mn of 3000 to 30 000 g / mol, more particularly of 4000 to 25 000 g / mol, most preferably of 5000 to 20 000 g / mol.

[0045] The polyurethane resin (A) preferably has a weighted average molecular weight Mw of 10 000 and 100 000 g / mol, more particularly from 20 000 to 80 000 g / mol, much more preferably from 30 000 to 60 000 g / mol.

[0046] Polyurethane resin (A) is prepared in accordance with the usual techniques of polymer chemistry. This means more particularly that the polymerisation of polyisocyanates and polyols form polyurethanes. These techniques are known to the skilled person and can be individually adapted according to the case in question. Exemplary preparation processes and reaction conditions can be found, for example, in European patent EP 0521 928 B1, page 2, line 57, page 8, line 16.

[0047] It is preferable to use polyurethane resins which have been prepared with the known techniques in organic solvents and then were converted into an aqueous dispersion by corresponding addition of water and distillation removal of the organic solvent. As is known, the resulting dispersions are also called secondary dispersions.

[0048] The fraction of at least one polyurethane resin (A) is preferably 5% to 40% by weight, more particularly 6% to 30% by weight, most preferably 7% to 20% by weight, based on each case, on the total amount of the primer composition of the invention.

ZINC PHOSPHATE (B)

[0049] An additionally essential constituent of the paint base component of the coating composition of the invention is zinc phosphate. Zinc phosphate is preferably used in forms, at least partially hydrated, in other words not in the form of anhydrous (dehydrated) zinc phosphate, exclusively, but with fractions of known zinc phosphate hydrates, that is, the mono -, di- and Tetrahydrate or mixtures thereof. These products are commercially available as white, powdered solids (one example being Zub phosphate ZP 10 from Heubach). These products are known to the skilled person and can be easily used in the coating composition of the invention. The average particle size of the zinc phosphate used is not really a critical parameter and is for example within the ranges, common for fillers and pigments, of a few micrometers (more particularly an average particle size (d50) of 0, 1 to 100 μm, preferably 0.1 to 50 μm, as measured by laser diffraction in accordance with ISO 13320: 2009). Zinc phosphate and / or its hydrates are used mainly in the form of powders, with particle sizes less than 100 μm, more particularly less than 50 μm, most preferably less than 35 μm. These particle sizes are checked by determining the sieve residue in accordance with DIN 53195: 1990-09. Whenever, in the case of a sample for which the sieve residue was measured using a sieve of defined mesh size, there is still a sieve residue of less than 0.1% by weight, that sample is considered for the purposes of the present invention by be a powder with particle sizes smaller than the mesh size of the respective sieve.

[0050] The fraction of zinc phosphate (B1) is preferably 2% to 30% by weight, more particularly 3% to 20% by weight, most preferably 4% to 15% by weight, based on each case, on the total amount of the inventive primer composition.

PIGMENT (C)

The primer composition of the invention additionally comprises at least one pigment (C). These pigments are known to the skilled person and are described for example in Rompp-Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, pages 176 and 451. Explicitly excluded from coloring pigments (C) are phosphate from zinc and its hydrates (B) and also the fillers (E) later described below. The pigments present are more particularly black pigments and / or white pigments. Preferably, therefore, the primer composition comprises at least one black pigment or at least one white pigment, or at least one white pigment and one black pigment. This means that the primer composition of the invention preferably has a gray, black or white color (in varying degrees). While a black or white color can be achieved with exclusive or almost exclusive (advantageously more than 95% by weight, based on the total quantity of the pigment) use of the pigments of the color in question, a gray color is obtained, for example, through the use of balancing mass fractions of black pigment and white pigment, with a black to white pigment weight ratio from 1:10 to 10: 1, for example, preferably 1: 5 to 5: 1, depending on the stage of desired gray and strength of the respective color pigments.

[0052] Preferred black pigments are the most typical organic and inorganic, black pigments more particularly inorganic, of the type commercially available as powders. Particularly notable are pigment grade carbon blacks (pigmented carbon blacks), iron oxide pigments (Fe3O4) such as typical synthetic iron oxides (available under the Lanxess trade name Bayferrox, for example), oxide pigments mixed as black manganese or spinel black. Especially preferred are pigment grade carbon blacks (pigmented carbon blacks) and iron oxide pigments.

[0053] Preferred white pigments are typical inorganic white pigments, such as, for example, titanium dioxide (examples being rutile pigments, known under the trade name Kronos of the company Kronos), zinc oxide, antimony trioxide or zinc sulfide. Especially preferred is titanium dioxide, more particularly in its modification of rutile.

[0054] The average particle size of the used pigments that are available in powder form, is not exactly a critical parameter and is located, for example, within the ranges, common for fillers and pigments, of a few micrometers (more particularly an average particle size (d50) from 0.1 to 100 μm, preferably from 0.1 to 50 μm, as measured by laser diffraction in accordance with ISO 13320: 2009). More particularly used as pigments are commercially available powders with particle sizes less than 100 μm, more particularly less than 50 μm (determination of the sieve residue in accordance with DIN 53195: 1990-09; see above).

[0055] The pigment fraction can vary widely and is preferably 0.1% to 20% by weight, more particularly 0.2% to 17.5% by weight, most preferably 0.3% to 15% by weight, based on each case, on the total amount of the inventive primer composition. In the case of white primers, a pigment fraction of 5% to 20% by weight, more particularly 8% to 15% by weight, is preferred. In the case of black primers, a pigment fraction of 0.1% to 5% by weight, more particularly 0.2% to 4% by weight, is preferred.

COMPONENT CONSTITUENTS (2) (HEALING COMPONENT)

[0056] In accordance with the invention, the curing component comprises at least one polyisocyanate (D1), as defined below, and at least one polyisocyanate (D2), which is different from them and is as defined below.

[0057] Polyisocyanates (D1) are isocyanurates based on hexamethylene diisocyanate (more precisely hexamethylene 1,6-diisocyanate, HDI).

[0058] As is known, isocyanurates of this type can be prepared in any of a wide variety of isocyanates in the presence of certain catalysts, examples being sodium formate, potassium acetate, tertiary amines or triphenylphosphines. In this case, very stable isocyanurate ring systems are formed, which are robust even at high temperatures above 100 ° C, for example, these systems, consisting of three isocyanate groups in each case. Each of these three isocyanate groups gives rise to three different molecules of the respective isocyanate used - that is, quarterly structures are formed. Considering that the use of monoisocyanates in each case produces molecules which are unequivocally defined by the respective chemical structural formula, the reaction in the case of polyisocyanates, such as diisocyanates such as HDI, for example, need not proceed in a uniform way and results more particularly in polyisocyanates more highly cross-linked, also called isocyanurates (for example, isocyanurate diisocyanates) or mixtures of different isocyanurate polyisocyanates. These products are, therefore, isocyanurates with a partially polymeric character which are based on a polyisocyanate, such as a diisocyanate. Depending on the choice of reaction conditions - known to you - and the reaction regime, this means, for example, that an isocyanurate trimer which has already been formed can attach additional diisocyanates, and which isocyanurate ring systems can form, with different products, having higher molecular weight, then being produced. At the same time, there is a reduction in the average number of isocyanate groups, compared to a monomeric diisocyanate. Considering that this number is precisely 1 in the ideal trimer, consisting of precisely three diisocyanate molecules, this number drops to less than 1 in highly cross-linked isocyanurate polyisocyanates. It is known to be possible, moreover, for fractions of deposition diols, such as hexanediol, for example, to be added during the preparation process, for the purpose, for example, of adjusting the reactivity of isocyanurates, and it is also known that in this way, two or more isocyanurate ring systems can be connected to each other.

[0059] The amount of isocyanate groups in polyisocyanates, such as diisocyanate isocyanurates - that is, for example, diisocyanate isocyanurate polyisocyanates - is, familiarly, generally expressed through the isocyanate content. The isocyanate content is the mass fraction of the free isocyanate groups in polyisocyanates, expressed as a percentage. For the purposes of the present invention it is determined experimentally, as previously described above.

[0060] From a particular diisocyanate, such as HDI, and then from this diisocyanate, preparing isocyanurates based on this diisocyanate, by the methods that are known to you and have already been elucidated above, especially isocyanurates with a polymeric character, the Isocyanate content reflects the degree of crosslinking of the respective isocyanurate or isocyanurate diisocyanate. The following instruction follows directly from what was described above: The lower the isocyanate content, the greater the crosslink density. Thus, for example, the theoretical isocyanate content of the trimeric isocyanurate purely based on HDI adopts the maximum value of about 25% (molecular weight 3 × NCO = 126 g / mol; molecular weight of the trimester isocyanurate purely from HDI = 504.6 g / mol).

[0061] The at least one isocyanurate based on HDI (D1) preferably has an isocyanate content of less than 22%, more particularly from 6% to 16%, most preferably from 8% to 13%. In this sense, at least one isocyanurate based on HDI (D1) is preferably an isocyanurate having a higher crosslink density compared to the pure trimer.

[0062] The fraction of at least one isocyanurate based on HDI is preferably 1% to 10% by weight, more particularly 1.5% to 7.5% by weight, most preferably 2% to 6% by weight, with basis in each case, on the total amount of the primer composition of the invention.

[0063] The HDI (D1) based isocyanurates described are commercially available, as, for example in solvent free form or as a solution in solvents which are known to you and are described later below and can be easily used in the composition of the invention's primer. Reference is made, for example, to commercial products from the Desmodur product line, an example being Desmodur N 3800, from Bayer.

[0064] Polyisocyanates (D2) are polyether modified isocyanurates based on isophorone diisocyanate (IPDI). For at least one isocyanurate based on IPDI (D2), the facts which apply in relation to the preparation and possible crosslinking with formation of isocyanurate diisocyanates having a plurality of isocyanurate ring systems per molecule, are the same as already described above for HDI isocyanurates. Another factor, however, is that at least one isocyanurate based on IPDI (D2) is modified by polyether.

This means that the isocyanurate contains polyether groups, examples being polyether chains, such as, more particularly, polyoxyethylene chains or polyoxypropylene chains. Modification of polyether polyisocyanates and / or isocyanurates in the context of the present invention refers more particularly to modification with alkoxypolyoxyalkylene groups, preferably methoxypolyoxyalkylene groups. The groups in question here are most preferably methoxy-polyoxyethylene groups and / or methoxypolyoxypropylene groups.

[0066] Hydrophilic modifications can be introduced using, for example, alkoxypoly (oxyalkylene) alcohols, which are known to the skilled person and are also commercially available. This is followed by the partial reaction of the isocyanate groups with the polymeric monoalcohols, which has the effect of attaching the polyether modifications - that is, for example, the poly (oxyalkylene) groups - covalently to the isocyanurate through the formation of urethane bridges . The formation of allophanate groups is also possible here, in which case this formation proceeds through an intermediate isocyanate dimerization with subsequent reaction with alcohol. It can be seen, therefore, that the hydrophilic modification removes isocyanate groups from the system and then leads to a reduction in the isocyanate content, in relation to the respective isocyanurate without modification. The underlying reactions of the modification and the reaction conditions to be selected here are known to the skilled person and can easily be adapted to the case in question. Hydrophilic modifications can be introduced according to the preparation, as described above, of isocyanurates and / or isocyanurate diisocyanates with polymeric character. It is also possible, of course, for simultaneous reaction of IPDI monomers with alkoxypoly alcohols (oxyalkylene), in which case the formation of isocyanurates and the bond between isocyanate groups and alkoxypoly alcohols (oxyalkylene) take place side by side.

[0067] The fraction of the modified isocyanate groups in the isocyanurate (D2) can vary widely and is for example in the range of 1-60 mol%, preferably 2 - 55 mol%, more preferably 5 - 50 mol%. The molar fraction indicated here refers to these free isocyanurate isocyanate groups prior to modification and therefore does not take into account, in particular, the groups attached in the isocyanurate ring system.

[0068] The at least one hydrophilic modified isocyanurate based on IPDI (D1) preferably has an isocyanate content of less than 17%, more particularly from 4% to 14%, most preferably from 7% to 12%.

[0069] The fraction of at least one hydrophilically modified isocyanurate based on IPDI (D2) is preferably 2% to 12.5% by weight, more particularly 3% to 10% by weight, most preferably 4% to 7.5 % by weight, based on each case, over the total amount of the inventive primer composition.

[0070] The hydrophilically modified isocyanurates based on IPDI (D2) described are commercially available, in the form, for example, of a solution in solvents which are known to you and are described later below and can be easily used in the primer composition of the invention. Reference is made, for example, to commercial products from the Bayhydur product line, one example being Bayhydur 401-70, from Bayer.

[0071] The combination of the two isocyanurates (D1) and (D2), in accordance with the invention, has resulted in particular from a well-considered balance between technological properties, more particularly anti-corrosion properties and good dispersion capacity in good water by isocyanates. In this way the anti-corrosion properties are combined with the aforementioned valuable environment profile.

[0072] The fraction of isocyanurates (D2) in the primer composition is preferably greater than the fraction of isocyanurates (D1).

[0073] It is essential for the invention that the molar amount of the isocyanate isocyanate groups present in the curing component (defined by the isocyanate content), more particularly of the polyisocyanates (D1) and (D2), is greater than the molar amount of hydroxyl groups. , which is linked with these NCO groups and are present in the base paint component (defined by the OH number), more particularly the OH groups of the polyurethane (A) resins. The NCO / OH stoichiometric ratio, more particularly the stoichiometric ratio from the isocyanate groups in the isocyanurates (D1) and (D2) to the hydroxyl groups present in at least one polyurethane resin (A), is greater than 2, more particularly greater than 2.5, more preferably greater than 3, most preferably 3, 5 to 10, even more preferably from 4 to 10 and, in a particularly preferred embodiment, 5 to 10.

[0074] Interestingly it has been found that an amount of isocyanate groups is greater in this way, more particularly an amount of the isocyanate groups of the isocyanurates (D1) and (D2), compared to the hydroxyl groups of the paint-based component, more particularly of at least one polyurethane resin (A), leads to particularly advantageous properties in relation to protection against corrosion and adhesion.

ADDITIONAL CONSTITUENTS OF THE PRIMER COMPOSITION OF THE INVENTION

[0075] The primer composition of the invention is aqueous. Aqueous is a familiar specification for the person skilled in coating compositions which comprise water as a solvent. Aqueous coating compositions (and, consequently, the primer composition) for the purposes of the present invention are identified more particularly as those containing at least 15% by weight of water, preferably at least 25% by weight, more preferably at least 35 % by weight of water, based on the total weight of the coating composition. With particular preference, aqueous media which in addition to the stated requirement "at least 15% by weight (or at least 25% or 35% by weight) of water, based on the total weight of the coating composition", an additional requirement that must to be fulfilled is that the fraction of organic solvents in the coating composition is less than 20% by weight, more particularly less than 15% by weight, most preferably less than 10% by weight, based on each case, on the amount total composition of the coating.

[0076] The solids content of the primer composition is preferably between 20% and 80%, more particularly 30% to 70%, very much, preferably between 40% to 60%.

[0077] The above ranges and limits related to the water content and the organic solvent content are more particularly synonymous with the fact that the primer composition can be produced in order to allow a VOC of less than 250 g / l achieved, or that the primer composition has a VOC of less than 250 g / l (as for the VOC definition See above).

[0078] As already described above, the specific upper emission limits for volatile organic substances, more particularly solvents, are nowadays established by the statute in the context of the operation of industrial painting plants. In addition, sufficient demonstration of compliance with the statutory provisions will be given. Particularly in the context of the simplified reduction plan, developed especially for painting plants in the smaller segment (automotive refinishing, for example), the acquisition of a legal license to operate such plants is linked to the use of coating compositions having a VOC of less than 250 g / l. Consequently, the primer composition of the invention is advantageous not only in relation to technological properties, such as adhesion and protection against corrosion, but also in relation to increasingly stringent legal provisions in the context of environmental protection.

[0079] As already indicated, moreover, that the primer composition of the invention can include at least one organic solvent. Organic solvents are used which do not inhibit the crosslinking of the primer composition and / or enter into any chemical reactions with other constituents of the primer composition. The skilled worker, therefore, is able to easily select suitable solvents based on their known solvency and reactivity. Examples of such solvents are aliphatic and / or aromatic hydrocarbons, such as toluene, xylene, naphtha solvents, Solvesso 100 or Hydrosol ® (from ARAL), ketones, such as acetone, methyl ethyl ketone or methyl amyl ketone, esters, such as acetate ethyl, butyl acetate, butylglycol acetate, pentyl acetate, methoxypropyl acetate or ethyl ethoxypropionate, ethers, alcohols, chlorinated hydrocarbons or mixtures of the aforementioned solvents.

[0080] The primer composition of the invention preferably additionally comprises at least one pad (E). This filling, where present, is preferably present in the base paint component of the primer composition. Fillers (E) which can ultimately be used are all organic and inorganic fillers that are known to you and are familiar with the skilled person, preferably inorganic fillers, for coating compositions. Explicitly excluded from fillers (E) are zinc phosphate and its hydrates (B) and also the coloring pigments (C) described earlier above. Fillers, therefore, include, more particularly, substances known to the skilled person that are used, for example, in granular or powder form, for the purpose of achieving specific physical properties of the coating compositions, and which are insoluble in the respective application. Such fillers include, more particularly, carbonates such as calcium carbonate or barium carbonate, sulfate such as calcium sulfate and barium sulfate, silicates and phyllosilicates such as talc, mica, pyrophyllite, calcium precipitate, aluminum, calcium / aluminum and sodium silicates / aluminum and mullite, silicas, such as quartz, cristobalite, silicas, or, more particularly, smoked silicas of the type that can be obtained, for example, under the trade name of Aerosil (from Evonik) and metal oxides and metallic hydroxides such as aluminum hydroxide and magnesium hydroxide, for example.

[0081] Especially preferred in the context of the present invention are silicon-based fillers such as silicon dioxide, silicates and phyllosilicates and also silicas such as, for example, the smoked silicas known by you (Aerosil from Evonik). These silicon-based fillers are optionally used in admixture with additional fillers such as preferably sulfates, such as barium sulfate, in the primer composition of the invention.

[0082] The particle size of the used ones that are available in powder form, is not exactly a critical parameter and is located, for example, within the ranges, common for fillers and pigments, of a few micrometers (more particularly an average size of particle (d50) from 0.1 to 100 μm, preferably from 0.1 to 50 μm, as measured by laser diffraction in accordance with ISO 13320: 2009). Most particularly used as fillers are commercially available powders with particle sizes less than 100 μm, more particularly less than 50 μm (determination of the sieve residue in accordance with DIN 53195: 1990-09; see above). However, as is to the knowledge of the skilled person, particle sizes are substantially smaller in the case, for example, of the smoked silicas declared as the commercially available products of Aerosil. The average particle sizes (d50) in this case are, for example, in the range 1 to 500 nm, more particularly 1 to 100 nm, preferably 5 to 50 nm (determined by means of photon correlation spectroscopy in accordance with DIN ISO 13321, October 2004).

[0083] The fraction of at least one filler (E) is preferably 5% to 45% by weight, more particularly 6% to 35% by weight, most preferably 7% to 25% by weight, based on each case, on the total amount of the primer composition of the invention.

[0084] In addition, the primer composition can also include at least one adjuvant. Examples of such adjuvants are salts that can be thermally decomposed without residue or substantially without residue, different binders from polyurethane resins (A), crosslinking agents other than polyisocyanates (D1) and (D2), such as melamine resins, reactive diluents, light stabilizers, antioxidants, release agents, emulsifiers, glide additives, polymerization inhibitors, radical polymerization initiators, adhesion promoters, flow control agents, film-forming assistants, thickeners, flame retardant agents, sag agents control systems (SCAs), corrosion inhibitors, waxes, biocides and matting agents. They are used in the usual and known amounts.

[0085] The solids content of the primer composition of the invention may vary according to the requirements of the case in question, more particularly within the preferred ranges specified above. The solids content is primarily guided by the viscosity that is required for the application, especially spray application and thus can be defined by the skilled person on the basis of their common general knowledge, optionally with the aid of some interval verification tests.

THE PRODUCTION OF THE PRIMER COMPOSITION OF THE INVENTION

[0086] The primer composition of the invention can be produced using the mixing methods and mixing sets that are usual and known for the production of coating compositions, such as agitation tanks, agitator mills, extruders, compounds, Ultraturrax devices , in-line dissolvers, static mixers, toothed dispersers, pressure release nozzles and / or microfluidizers. Here it should be borne in mind that the primer composition of the invention is a 2K coating composition, and that component (1) (paint base component) and component (2) (curing component) are stored separately from each other and , as described above, not combined and mixed until just before application of the primer composition. Here, in general, the basic paint component covers not only the essential inventive constituents (A), (B), (C) and water, but also any adjuvants present. This paint-based component is then mixed, just before the application of the primer composition, with the curing component, which is usually composed of organic solvents, as well as the inventively essential constituents (D1) and (D2).

[0087] In advantageous embodiments of the invention, base components of black and white paint are prepared (comprising exclusively or almost exclusively (advantageously more than 95% by weight, based on the total amount of the pigment) black pigments or white pigments). These paint-based components can then be mixed in any desired proportions with one another, thus producing paint-based components in various gray stages in a simple way. It is an advantage of the invention, therefore, that base paint components and, therefore, primer compositions in different stages of achromatic lightness can be produced in a simple way. In this way, the primer composition can then be optimally adapted in terms of its lightness to any additional coloring coat compositions, to be applied after the primer composition and described later below, more particularly base coat materials, with the system resulting multi-coating then having, as a result, excellent coloring and color depth.

THE METHOD OF THE INVENTION

[0088] In addition, the present invention provides a method for producing a coating on a substrate, applying the coating composition of the invention directly to a substrate and then forming a coating film. In the context of the method of the invention in which the primer composition is used, of course, the particular and preferred modalities described above for the primer composition likewise apply.

[0089] Applying directly means that, before applying the primer composition, no other coating composition is applied that is capable of forming a polymeric organic matrix, and no conventional conversion coating composition (in the form of phosphating, for example) is applied. The anticorrosive primer composition, therefore, is the first coating composition applied. More particularly, no electrocoat layer is applied.

[0090] Application of the substrate primer composition of the invention can happen in the film thicknesses that are usual within the vehicle industry, in the range, for example, from 5 to 200 micrometers, preferably from 10 to 100 micrometers, more preferably from 20 at 60 micrometers, most preferably from 30 to 50 micrometers. The indicated film thicknesses should be understood as dry film thicknesses, after curing described below. The techniques used in this context are, for example, the techniques known as spraying, knife coating, spreading, pouring, dipping, impregnation, dripping or rolling. Spraying techniques are used with preference.

[0091] After the primer composition of the invention has been applied, a polymer film or coating film is formed from it. That is, the applied primer composition is cured by known techniques. Curing occurs preferably at temperatures of 10 to 200 ° C, more particularly 10 to 100 ° C, much, preferably from 20 to 80 ° C. These preferred, very low curing temperatures are a particular consequence of the fact that the primer composition is a 2K coating composition for which only low curing temperatures are necessary, particularly for the external thermal crosslinking of the hydroxyl groups of the resin. of polyurethane (A) and the isocyanate groups of the polyisocyanates (D1) and (D2). The duration of the cure can vary widely from case to case and is for example between 1 minute and several hours, more particularly between 5 minutes and 120 minutes.

[0092] Depending on the case in question, curing can optionally be preceded by flashing at, for example, room temperature (about 15 to 25 ° C) for 1 to 60 minutes, for example. Flashing for the purposes of the present invention represents the evaporation of organic solvents and / or water, rendering the coating material dry, but not yet cured - in particular, no fully cross-linked coating film is formed at this time.

[0093] Curing then produces the coated substrate of the invention, which is also provided by the present invention. The present invention also provides a coating produced from the primer composition.

[0094] After the primer composition has been cured, more usual and known coating compositions capable of forming a coating layer, based on a polymeric matrix can be applied and cured by usual and known techniques, to produce a multi-coating system . The associated dry film thicknesses of the respective individual coatings are within the usual ranges - for example, between 5 to 200 micrometers, more particularly between 5 and 100 micrometers. These coatings can be produced by successive application of the individual coatings, without complete curing in each case, followed by curing in a joint curing process (wet on wet process). Complete individual curing of the coatings in each clear case is also possible.

[0095] In a particularly preferred embodiment of the present invention, a multi-coated coating is produced on a substrate by applying the additional coating compositions prior to complete curing of the primer composition. This means that the primer composition is merely flashed out beforehand (wet on wet process). In particular, the coatings that follow are then applied in the same way by the wet-on-wet process, and then, after application and optional flashing of the last coating composition, all applied coating compositions, including the primer composition, are cured.

[0096] In the automotive industry, where the primer composition of the invention is preferably employed, the more coating compositions can be, as is known, customary leveler primer coatings, base coatings and transparent coatings. With a very particular preference, however, the system in question is a multi-coated coating system comprising the primer composition of the invention, a matte base and a varnish, and which mainly consists of these three coatings .. This multi-coating system , which, in contrast to the usual multi-coated automotive coating (which includes a conversion coating, electrocoating, leveling primer coating, matte base and transparent coating), consists of only three individual coats, however, has excellent performance properties, especially with regard to resistance to salt water and condensation. The primer composition of the invention likewise unites the performance properties of conversion coating (especially in the form of phosphating) electrocoating and leveling primer coating in one and therefore offers great advantages.

[0097] The substrates used are metallic substrates, preferably those used in the context of the automotive industry (vehicle construction). It is advantageous to use alloyed and unalloyed steels and / or substrates of iron, zinc and aluminum and corresponding alloys.

[0098] In a particular embodiment of the present invention, the substrates in question are metallic substrates that have already been completely painted, more particularly with multi-coated automotive finish and where the respective multiple coating exhibits local instances of damage. More particularly, therefore, it consists of automobile bodies or their parts that have damage cases, such as dent damage and the like, for example. Within the damaged regions, therefore, the original multi-coated coating has suffered at least partial detachment as a result of external exposure. The primer composition of the invention is used to repair these damaged regions, in other words in touch-up. In general, the touch-up procedure, the application of the primer composition is preceded by cleaning and abrasion of the damaged substrate, originally coated. In this procedure, any regions of the original present coating that are not sufficiently adhering and have suffered partial detachment and / or corrosion products that have already formed are removed, and more particularly the metallic substrate is exposed locally. Therefore, the method of the invention, as well, which involves applying the primer composition directly to the substrate, is used advantageously in the context of overcoating, more particularly automotive overcoating. In the context of overcoating more particularly, the primer composition of the invention and also the method of the invention hold great advantages, since specifically this demanding sector, the reduction of the number of coatings that require individual application for the purpose of repairing the multi-coating system massively facilitates work and makes it quicker to perform and therefore more favorable from an economic point of view. A particular advantage in this context is also the fact that the primer composition can be applied wet on wet and, therefore, there is no need to intercalate abrasion of the layer, as would be the case in the case of complete curing before applying compositions. additional coatings. The primer composition of the invention and the method of the invention lead to coatings that exhibit excellent adhesion and corrosion resistance. The present invention therefore also provides for the use of the primer composition and also of the method for increasing corrosion resistance, especially in the context of automotive finish.

[0099] The text below, the invention is illustrated through examples.

EXAMPLES A) preparation of inventive primer compositions (1) and (2)

1 parâmetros: número de OH (resina) = 17 mg KOH/g, número ácido (resina) = 25 mg KOH/g, Mn (resina) = 7800 g/mol, Mw (resina) = 49 000 g/mol.

[00100] The components (1) (paint base component) and (2) (curing component) of a white inventive primer composition and a black inventive primer composition were prepared by combining the respective constituents and subjecting them to intimate mixture in a solvent.
The constituents and their quantities can be seen in tables 1 and 2. Considering that the base paint components of the two inventive primer compositions differ from each other, the curing component selected in each case was the composition indicated in table 2.

1 parameters: OH number (resin) = 17 mg KOH / g, acid number (resin) = 25 mg KOH / g, Mn (resin) = 7800 g / mol, Mw (resin) = 49 000 g / mol.

[00101] For the preparation of the inventive primer compositions (1) (white) and (2) (black), the base paint components (white) and (black) were in each case mixed with the curing component and , also, with water in a solvent. The mixing ratios can be seen in table 3. The stoichiometric NCO / OH ratios of the isocyanate groups in the isocyanurates (D1) and (D2) and also of the hydroxyl groups present in at least one polyurethane resin (A) in the inventive primer compositions they are 6.5 (primer composition (1) (white)) and 8.2 (primer composition (2) (black)). Within an hour after their preparation, the primer compositions were used as described under B) - in other words, applied directly to a metallic substrate and then cured, in the production of multi-coated coating systems.

B) production of inventive multi-coated coating systems (M1) and (M2) by the inventive method

[00102] The primer compositions (1) and (2) described under A) were pneumatically applied directly to iron panels and aluminum panels and also to galvanized steel panels. Before application, these panels were merely cleaned or degreased and subsequently used with sandpaper. More particularly, there was no conversion coat (phosphating, for example) and / or electrocoat produced. Application was followed by flashing at room temperature (RT) for 30 minutes, after which a commercial 2K water-based matte material was applied pneumatically and flashed again at RT for 15 minutes. This was followed by the pneumatic application of a transparent 2K commercial coating material and again by flashing at RT for 5 minutes and finally by curing the coating system at 60 ° C for 30 minutes. The associated dry film thicknesses of the individual coatings of the multi-coated coating systems (M1) (white) and (M2) (black) thus produced were 40 micrometers (primer composition (1) for the multi-coating system (M1), composition of primer (2) for the multi-coating system (M2), 12 micrometers (matte base) and 40 micrometers (transparent coating).

C) Production of additional multi-coating systems

[00103] In addition, additional comparative and inventive (non-inventive) multi-coating systems were produced. Production took place along the lines of the production method described under B), using different primer compositions. Additional multi-coating systems are illustrated below, with changes compared to the multi-coating systems (M1) and (M2) being indicated. These changes refer in particular to the primer composition used in its production and, therefore, lead to a change in the resulting multi-coating system.

[00104] (M3): The inventive multi-coated coating system (M3) was produced in the same way as for the production of (M2), but the stoichiometric NCO / OH ratio of the isocyanate groups in the isocyanurates (D1) and (D2) for the hydroxyl groups present in the polyurethane resin (A) in the primer composition of the invention it was 5.3. The lower fraction of isocyanurates in this case was compensated by a corresponding amount of Solvesso 200 / Butylglycol acetate of 1: 1 (v / v).

[00105] (M4): The inventive multi-coated coating system (M3) was produced in the same way as for the production of (M2), but the stoichiometric NCO / OH ratio of the isocyanate groups in the isocyanurates (D1) and (D2) for the hydroxyl groups present in the polyurethane resin (A) in the primer composition of the invention it was 4.1. The lower fraction of isocyanurates in this case was compensated by a corresponding amount of Solvesso 200 / Butylglycol acetate of 1: 1 (v / v).

[00106] (CM1): The comparative multi-coating system (CM1) was produced in the same way as for the production of (M2), but using, instead of an inventive primer composition, a primer composition in which the ratio of stoichiometric NCO / OH of the isocyanate groups in the isocyanurates (D1) and (D2) for the hydroxyl groups present in the polyurethane resin (A) in the primer composition was 1.8. The lower fraction of isocyanurates in this case was compensated by a corresponding amount of Solvesso 200 / Butylglycol acetate of 1: 1 (v / v).

[00107] (CM2): The comparative multi-coating system (CM2) was produced in the same way as for the production of (M2), but using, instead of the inventive primer composition, a standard solvent-based primer composition primer based on phosphoric acid / polyvinyl butyral (to produce a primer coating on the substrate) and a standard solvent-based primer based on polyurethane (for the production of primer on the primer coating and under the matte base).

[00108] (CM3): The comparative multi-coating system (CM3) was produced in the same way as for the production of (M2), but using, instead of an inventive primer composition, a primer composition that contained only one polyisocyanurate (D2) (Bayhydur 401-70) and non-polyisocyanurate (D1) (Desmodur N 3800). The NCO / OH ratio, however, was kept constant by means of a correspondingly larger fraction of Bayhydur 401-70. The general amount of isocyanurates in this case was compensated for by a correspondingly smaller amount of Solvesso 200 / Butylglycol acetate of 1: 1 (v / v).

[00109] (CM4): The comparative multi-coating system (CM4) was produced in the same way as for the production of (M2), but using, instead of an inventive primer composition, a primer composition that contained only the polyisocyanurate (D1) (Bayhydur 401-70) and no polyisocyanurate (D2) (Desmodur N 3800). The NCO / OH ratio, however, was kept constant by means of a correspondingly greater fraction of Desmodur N 3800. The overall amount of isocyanurates in this case was compensated by a correspondingly greater amount of Solvesso 200 / Butyl glycol acetate 1: 1 (v / v). Because of a poor water dispersion capacity, the primer composition produced in this way cannot be obtained in a phase as homogeneous as was the case for primer compositions composed of two polyisocyanurates. After application and curing, the coating film exhibited a homogeneous structure. In this sense, performance investigations have not been carried out.

D) investigation of the coatings produced

[00110] The multi-coated coating systems (M1), (M2), (M3) and (M4) and also (CM1), (CM2) and (CM3), have been subjected to performance investigations for their adhesion properties and the associated corrosion resistance.

[00111] For this purpose, substrates coated with multi-coated coating systems were first stored for 10 days in wet conditions (ISO 6270) (condensation test).

[00112] The multi-coating systems were subsequently inspected for any bubbles that may have occurred. In addition, adhesion was investigated using the cross-sectional test (DIN EN ISO 2409). In the same way, the extensive test was performed, which is similar to the cut test but in which only a transversal cut is made on the coated surface, using a cutting blade (respective cut length 5 cm). An adhesive tape is then applied to the surface and subsequently removed again by pulling suddenly.

[00113] The basis for the results of these tests were the following evaluation scales, which allow corresponding conclusions on adhesion and corrosion, protective properties.

• -m0 para m5 (quantidade de bolhas, onde 0 = sem bolhas, 5 = muito grande número de bolhas);
• -g0 a g5 (tamanho das bolhas, onde 0 = muito pequenos ou sem bolhas, 5 = muito grandes bolhas).

[00114] Bubble test:

• -m0 to m5 (number of bubbles, where 0 = no bubbles, 5 = very large number of bubbles);
• -g0 to g5 (size of bubbles, where 0 = very small or no bubbles, 5 = very large bubbles).

• -GT0 para GT5, onde GT0 = bordas cortadas completamente lisas e sem delaminações, GT5 = muito graves fragmentações e delaminações nas bordas cortadas, destacamento de regiões inteiras.

[00115] Cross section:

• -GT0 for GT5, where GT0 = cut edges completely smooth and without delamination, GT5 = very serious fragmentation and delamination at cut edges, detachment of entire regions.

• -0 para 5, onde 0 = bordas cortadas completamente lisas e sem delaminações, 5 = muito graves fragmentações e delaminações nas bordas cortadas, destacamento de regiões inteiras.

[00116] Hatch:

• -0 to 5, where 0 = cut edges completely smooth and without delamination, 5 = very serious fragmentation and delamination at cut edges, detachment of entire regions.

[00117] In addition, substrates coated with multi-coated coating systems (M1), (M2), (M3), and (M4) and also (CM1), (CM2) and (CM3), were investigated by spraying tests of salt according to DIN EN ISO 9227.

b) aço galvanizado

c) Substrato de alumínio

[00118] Table 4 shows the results obtained.

b) galvanized steel

c) Aluminum substrate

[00119] The results established in table 4 show that the inventive multi-coated coating systems, produced using aqueous inventive primer composition on different metallic substrates by the inventive method, exhibit excellent adhesion properties and, therefore, have very good corrosion resistance. In particular, it is apparent that the high NCO / OH ratio in accordance with the invention leads to very good properties. The properties, moreover, are comparable or even better than the properties achieved through the use of usual primers and solvent-based primer compositions. Therefore it is evident in general through the use of the primer composition of the invention it is possible to combine a valuable environment profile with a simplified multi-coating procedure, however, resulting in excellent adhesion and anti-corrosion properties.

Claims (16)

TWO COMPONENT WATER PRIMER COMPOSITION, characterized by comprising:
(1) a base paint component comprising

• (A) at least one polyurethane resin having an OH number of 5 to 60 mg KOH / g,
• (B) zinc phosphate,
• (C) at least one pigment,

and
(2) a healing component comprising
(D1) at least one polyisocyanate which is an isocyanurate based on hexamethylene diisocyanate,
(D2) at least one polyisocyanate which is a modified polyether isocyanurate based on isophorone diisocyanate,
where the stoichiometric ratio of isocyanate groups of isocyanurates (D1) and (D2) to hydroxyl groups present in at least one polyurethane resin (A) is a ratio greater than 3 to a ratio of 10. COMPOSITION according to claim 1, characterized in that the at least one polyurethane resin (A) has an OH number of 10 to 40 mg KOH / g. COMPOSITION according to any one of claims 1 to 2, characterized in that the at least one polyurethane resin (A) has an acid number of 5 to 80 mg KOH / g. COMPOSITION according to any one of claims 1 to 3, characterized in that the fraction of the at least one polyurethane resin (A) is from 6% to 30% by weight, based on the total amount of the primer composition. COMPOSITION according to any one of claims 1 to 4, characterized in that the fraction of zinc phosphate (B) is 3% to 20% by weight, based on the total amount of the primer composition. COMPOSITION according to any one of claims 1 to 5, characterized in that pigments (C) are selected from the group of black and white pigments. COMPOSITION according to any one of claims 1 to 6, characterized in that the at least one isocyanurate (D1) has an isocyanate content of 8% to 13%, and the at least one polyether modified isocyanurate (D2) has a content 7 to 12% isocyanate. COMPOSITION according to any one of claims 1 to 7, characterized in that the fraction of the at least one isocyanurate (D1) is 1.5% to 7.5% by weight, and the fraction of the at least one hydrophilically modified isocyanurate (D2 ) be 3% to 10% by weight, based on each case, over the total amount of the primer composition. COMPOSITION according to any one of claims 1 to 8, characterized in that a padding (E) is additionally comprised. COMPOSITION according to any one of claims 1 to 9, characterized in that the stoichiometric ratio of the isocyanate groups of the isocyanurates (D1) and (D2) to the hydroxyl groups present in at least one polyurethane resin (A) is from 4 to 10. COMPOSITION according to any one of claims 1 to 10, characterized in that it comprises at least 25% by weight of water, based on the total weight of the primer composition, and in which the fraction of organic solvents, based on the total weight of the composition of primer, is less than 15% by weight. METHOD TO PRODUCE A COATING characterized by:

• (1) applying a primer composition, as defined in any one of claims 1 to 11, directly to a metallic substrate, and
• (2) forming a polymer film from the primer composition applied in stage (1).

METHOD, according to claim 12, characterized in that the substrate is a metallic substrate coated with an automotive finish, the automotive finish having local instances of damage and the method being used as part of the repair of the damaged regions, in other words the touch-up. METHOD according to any one of claims 12 to 13, characterized in that the application of the primer composition is followed by the application of at least one additional coating composition which is cured together with the applied primer composition. METHOD according to claim 14, characterized in that the two additional coating compositions are applied, the first additional coating composition being a matte base material and the second additional coating composition being a transparent coating material. COATED SUBSTRATE, characterized by being coated by the method, as defined in any one of claims 12 to 15.