Aqueous coating composition comprising an epoxy resin-based binder component

Abstract

The present invention relates to a specific aqueous two-component coating composition, which comprises a binder component (1) based on epoxy resin and a curing component (2) based on polyamine, wherein the binder component (1) comprises at least one aqueous dispersion of at least one pigment (P) and / or filler (F) in at least one epoxy resin (E), wherein the at least one epoxy resin (E) has (i) a maximum sedimentation velocity of not more than 17500 μm / h and a glass transition temperature of less than 0° C., or (ii) a maximum sedimentation velocity of at least 12500 μm / h and a glass transition temperature of at least 0° C.

Description

[0001] The present invention relates to an aqueous coating composition comprising a specific epoxy resin-based paint base component and a polyamine-based curing component. The coating composition has excellent applicability as an aqueous sanding surface primer or a first surface primer. Therefore, by applying the coating composition to a substrate and subsequently curing, a surface primer layer with excellent adhesion and corrosion resistance can be obtained. However, more particularly, what is obtained is a surface primer layer with excellent surface quality and in particular almost no visual defects such as holes or even completely free of such defects. In this way, an overall coating system architecture with corresponding excellent optical quality can be finally obtained. In addition, the surface primer layer has excellent sanding properties and therefore has very good applicability, especially in the field of repair. Prior art

[0002] In principle, waterborne surfacers and primer-surfacers are known which cure on the basis of epoxy-amine combinations and can in this way form corrosion-stable surfacer or primer-surfacer hybrid layers. Their property profile is rather complex and they have the special features of the already mentioned corrosion stability and good adhesion to various substrates such as steel, galvanized steel, aluminum, electrophoretic coatings and old paint systems.

[0003] Another important property of these systems is that the surfacer layers built up in the automotive recoat sector should have acceptable sandability, even after curing at moderate temperatures and within the usual processing times in a paint shop. This sandability is very important in the process sequence of painting in order to produce a uniform surface for the subsequent layers such as basecoat and clearcoat and ultimately give the painted surface an aesthetically high-quality appearance.

[0004] However, it should be noted that, for this aesthetic appearance, it is also important that the surfacer layer itself is substantially free of visual defects, such as holes. It is clear here that the systems of the prior art generally have weaknesses.

[0005] WO 97 / 49749A1 discloses coating compositions based on waterborne epoxy systems containing specific epoxy-aminocarbamate adducts as curing agents. These are obtained by reacting very specific aminocarbamate compounds with epoxy compounds. Epoxy compounds are obtained by reacting polyalkylene polyethers with one or more amino groups. These adducts are used for waterborne two-component paints, especially automotive paints. The paints or paint coatings thus prepared have good sanding properties. It is said that the paints described in EP0387418A2 have disadvantages in their sanding properties.

[0006] EP 0387418 A2 discloses a curing agent for epoxy compounds and their use for the preparation of coatings and coverings. The curing agent is prepared by reacting a polyalkylene polyether amine with a stoichiometric excess of a di- and / or polyepoxide and then reacting the adduct with a stoichiometric excess of the amine. The coating compositions prepared with these curing agents have good storage stability and good curing properties. There is no mention of recoating, nor of the sandability of the coating or of the use of the curing agent in a surfacer.

[0007] EP 0610787 A2 describes a curing agent for aqueous epoxy resin dispersions which is obtained by reacting an adduct (A) of a polyepoxide and a polyalkylene polyether polyol with a reaction product of an amine and an epoxide, or with an amine and subsequently with an epoxide, the amine being used in each case in a stoichiometric excess. The problem to be solved is, for example, to achieve good adhesion and hardness in coating compositions comprising surfacers.

[0008] EP 0523610A1 describes an epoxide / amine-based coating composition which produces a smooth, defect-free surface after application. This is achieved by using a polyurethane resin in the coating composition.

[0009] US 2006 / 0003166A1 describes a composition for preparing a primer and / or a surfacer, which is likewise based on epoxides / amines. The composition enables the construction of coatings having good sag resistance. This is achieved by using a specific polyamine component.

[0010] Problems and technical solutions

[0011] The problem underlying the present invention was therefore to eliminate the disadvantages of the prior art and to provide an aqueous coating composition which, after application and curing, has good adhesion, corrosion protection and possible sandability, in particular in the case of automotive repainting, and furthermore has an excellent surface quality without surface defects such as pores. The composition is therefore particularly suitable as a surfacer and primer-surfacer or for producing a surfacer layer in a multicoat paint system.

[0012] It has been found that the object is achieved by a novel aqueous two-component coating composition comprising:

[0013] (1) a paint base component based on epoxy resin, and

[0014] (2) a polyamine-based curing component,

[0015] wherein the binder component (1) comprises at least one aqueous dispersion of at least one pigment (P) and / or filler (F) in at least one epoxy resin (E),

[0016] And wherein the at least one epoxy resin (E) has:

[0017] (i) a maximum sedimentation rate not exceeding 17,500 μm / h (measured in an optical cuvette centrifuge at an acceleration of 2,050 g, diluted to 30% solids with water) and a glass transition temperature less than 0°C (measured by dynamic differential calorimetry with a heating rate of 10 K / min, run 2), or

[0018] (ii) a maximum sedimentation rate of at least 12500 microns / hour and a glass transition temperature of at least 0°C.

[0019] The novel aqueous two-component (2K) coating composition is the subject of the present invention and is also referred to as the coating composition of the present invention. The present invention also provides a method for producing a cured coating on a substrate using the coating composition. The present invention also provides a method for repairing a multilayer paint system having defects using the coating composition. The present invention also provides a coating produced as described above and a coated substrate.

[0020] It has surprisingly been found that the use of only specific epoxy resins (E) in the binder component for dispersing pigments and / or fillers leads to coating compositions which can both be properly prepared using standard dispersing and grinding methods (i.e., in particular without rheological degradation processes in the grinder, which lead to a paint that is only difficult to process, if at all), and which, after application and curing, give a paint layer having excellent properties and which is also essentially free of pores. In some cases, the use of other epoxy resins does not even allow the binder component to be properly prepared by the necessary dispersion, or, if dispersion is possible, leads to a paint having very poor properties. The use of the necessary polyamine components corresponding to the epoxy resins for dispersion in the binder component leads to paints having properties that are in principle acceptable, but with the disadvantage that the paint has many micropores.

[0021] Detailed Description

[0022] The preferred aqueous resin dispersion (AD) is

[0023] The coating composition of the present invention preferably comprises a specific aqueous dispersion (AD) containing a resin component (R).

[0024] The term "aqueous" relevant to dispersions such as resin dispersions, phases or other aqueous coating compositions is known in principle. It means a dispersion or mixture containing a significant proportion of water as a solvent. It should be understood that, for aqueous systems, at least a small amount of organic solvents may also be contained, for example as a cosolvent with an emulsifier function to stabilize a specific component such as a resin, a pigment or an additive. In the context of the present invention, "aqueous" should preferably be understood to refer to the system in question, especially dispersions, with at least 40 weight %, preferably at least 50 weight %, even more preferably at least 60 weight % of the water in the ratio, in each case based on the total amount of the solvent (i.e. water and organic solvent) present. The ratio of preferred water is 50-99 weight %, in particular 60-98 weight %, in each case based on the total amount of the solvent present.

[0025] According to definitions known in principle, resins or resin components are also understood to mean products containing organic constituents, i.e. organic reaction products, oligomers and / or polymers and, if appropriate, monomers, as with the resin component (R). Resins have a more or less broad molar mass distribution and can generally be used as binders in coating compositions. Thus, after curing, they form the polymer network of at least a portion of the coating present.

[0026] The resin component (R) contains at least one di- and / or polyfunctional monomeric primary and / or secondary amine (M), ie at least one monomeric amine comprising at least two amino groups selected from primary and secondary amino groups. Of course, the additional presence of tertiary amino groups is not impossible.

[0027] In the context of the resin component (R), it is important that the total amines (M) used and therefore present in the aqueous dispersion (AD) consist of at least 65 mol % of amines consisting of amino and hydrocarbon units. This means that other functional groups, in particular for example hydroxyl, carboxyl or nitrile groups, are present only in small amounts. Preferably, the amines (M) consist of at least 75 mol %, more preferably at least 90 mol %, of amines consisting of amino and hydrocarbon units. Most preferably, the proportion of these amines is 100 mol %.

[0028] The proportion of the corresponding amines can be explained essentially by itself from the amounts of amines used. However, when using products such as commercial products, the proportion of the corresponding amines can also be determined by analyzing the products (in which the amines may also be partially or completely covalently bonded to one another) to such an extent that the above conditions are clearly met directly (e.g. by gas chromatography (GC), mass spectrometry (MS) analysis).

[0029] Examples of suitable amines (M) are the monomeric aliphatic, aromatic and araliphatic (mixed aliphatic-aromatic) amines known in principle to the person skilled in the art.

[0030] Examples of di- and / or polyfunctional monomeric primary and / or secondary amines include the following: ethylenediamine, propylene-1,2-diamine, propylene-1,3-diamine, butane-1,4-diamine, octane-1,8-diamine, 1,3-diaminopentane, hexamethylenediamine, 2-methylpentamethylenediamine, neopentyldiamine, cyclohexanediamine, 2,2,4-(2,4,4-)trimethylhexamethylenediamine, isophoronediamine, bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, bis(hexamethylenediamine), N,N-dimethylaminodipropylenetriamine, laurylpropylenediamine, 1,2- and 1,3-(m-)-phenylenediamine and 1,4-bis(aminomethyl)benzene. Other amines include aminoethylethanolamine or heterocyclic polyamines such as aminoethylpiperazine and bis(aminopropyl)piperazine.

[0031] Preferred are difunctional primary and / or secondary amines (M), more preferably difunctional primary amines. Very particular preference is given to isophoronediamine and meta-xylylenediamine, and the resin component more preferably comprises a mixture of the two diamines. This means, therefore, that the amine (M) is a mixture of isophoronediamine and meta-xylylenediamine.

[0032] The proportion of the at least one di- and / or polyfunctional monomeric primary and / or secondary amine (M) is 5-15% by weight, preferably 6-14% by weight, more preferably 7-13% by weight (test methods see Examples section), based on the resin component (R).

[0033] As can be seen from the synthesis methods of steps (A) and (B) described in more detail below, in step (A), the above-mentioned di- and / or multifunctional monomeric primary and / or secondary amines (M) (referred to as component (Ib) in step (A)) as reactants reacting with the epoxy-functional resin mixture (Ia) are partially reacted and, in step (B), further reacted with the additional epoxy compound (IIb) in the aqueous phase. The resin component (R) finally obtained then contains the above-mentioned proportion of at least one di- and / or multifunctional monomeric primary and / or secondary amine (M). It is therefore clear that the proportion of monomeric amines (M) in the resin component (R) is the remaining proportion of the amines (M) initially used for the reaction in step (A).

[0034] The resin component (R) also contains polyfunctional polymeric organic amines with primary and / or secondary amino groups. Thus, in contrast to the monomeric amines already described, these are not low molecular weight compounds with a discrete number of amino groups per molecule (constant for each molecule), but rather adducts or reaction products with polymeric properties, and in which the number of amino groups per molecule can only be described by an average value.

[0035] In this regard, the structure of the components described here, i.e. the structure of the polyfunctional polymeric organic amines having primary and / or secondary amino groups, is apparent from the synthetic methods of steps (A) and (B) described in more detail below. The starting compounds used to prepare the resin component (R) show what structural units the polyfunctional amines mentioned here have.

[0036] The resin component (R) has an NH equivalent weight of 150-400 g / mol, preferably 160-350 g / mol, more preferably 170-250 g / mol (for the determination method, see the Examples section).

[0037] The aqueous dispersion (AD) comprising the resin component (R) can be prepared by a two-step process (A+B). It is obvious to the person skilled in the art that a full description of the dispersion by purely structural features and / or by the characteristics of the dispersion based on parameters is very difficult and that a description of the reaction steps and their sequence is sensible for this purpose. It is therefore also obvious that the reaction sequence described below has a direct influence on the structure of the resin component (R) and therefore on the dispersion (AD).

[0038] Step A

[0039] In the first step (A) of the reaction sequence, two starting components (Ia) and (Ib) are reacted with one another, namely an epoxy-functional resin mixture (Ia) and a component (Ib) containing at least one di- and / or polyfunctional monomeric primary and / or secondary amine. This results in an amino-functional resin mixture (I). It is therefore obvious that the amounts of components (Ia) and (Ib) are matched to one another so that the NH equivalents of component (Ib) are in molar excess relative to the epoxy groups of component (Ia).

[0040] The epoxy-functional resin mixture (Ia) comprises two components (Ia1) and (Ia2) in mutually reacted form, as described below. The resin mixture (Ia) preferably consists of these two components, ie is prepared exclusively by reaction of these two components.

[0041] Component (Ia1) is at least one di- and / or polyfunctional organic epoxy compound.

[0042] Therefore, the components (Ia1) that can be used are in principle known epoxy resins. Preferably, the average epoxy equivalent of these epoxy compounds used is less than 400 g / mol. It has been found that the correspondingly low average epoxy equivalent and therefore the higher epoxy functionality of this component also lead to better sanding properties in the final surface primer layer. More preferably, the average epoxy equivalent is less than 350 g / mol, preferably less than 300 g / mol, more preferably less than 250 g / mol. The average epoxy equivalent can be obtained by determining the epoxy equivalent of all epoxy compounds used (for test methods, see the Examples section) and weighting their mass proportion in the total weight of epoxy compounds. When using existing products such as commercial products (in which the epoxy compounds may have been covalently bonded), the average epoxy equivalent can also be determined by analyzing the product to an extent that it is immediately clear that it is below the above-mentioned upper limit (for example, by gas chromatography (GC), mass spectrometry (MS) analysis).

[0043] Known epoxy resins are polycondensation resins which contain, on average, more than one epoxy group in the base molecule. These are, for example, epoxy resins prepared by condensation of bisphenol A or bisphenol F with epichlorohydrin. These compounds contain hydroxyl groups along the chain and epoxy groups at the ends. Depending on the chain length of the epoxy resin, there is a variation in the crosslinking capacity via the epoxy groups, since the crosslinking capacity via the epoxy groups decreases with increasing chain length / molar mass. Ultimately, any epoxy resin known per se to the person skilled in the art can be used, provided that they are within the above-mentioned epoxy equivalent range. For example, commercially available epoxy resins mentioned further below can be used, which are available as solutions or dispersions in organic solvents or water.

[0044] Such epoxy resins are available, for example, as 100% systems or solutions or dispersions in organic solvents or water, for example under the trade name Beckopox EP from Allenex (or under the trade name Epikote / EPI-REZ from Huntsman Group's Hexion / Araldite).

[0045] Preferred components (Ia1) are averagely difunctional epoxides, since this is formed via epichlorohydrin in the above-mentioned standard synthesis.

[0046] Furthermore, it is preferred that the epoxy compound (Ia1) is a bisphenol A-based epoxy compound, i.e. an epoxy compound prepared by using bisphenol A. More particularly, this means that the epoxy compound does not contain any bisphenol F introduced via synthesis. It has been found that this result in turn has a positive effect on the sandability of the surfacer layer finally produced.

[0047] Component (Ia2) is at least one compound XR in which X is a functional group reactive toward epoxy groups and R is an organic group containing polyoxyalkylene units and no further X groups. Preference is given to using exactly one compound XR as component (Ia2).

[0048] The X groups are groups known to the person skilled in the art, for example primary or secondary amino, hydroxyl, carboxyl or thiol groups.

[0049] It is essential that the compound XR has only one X group. Otherwise, it has been found that the sandability of the resulting surfacer layer is adversely affected.

[0050] Preferred X groups are amino groups, with primary amino groups being preferred. In addition to the good reactivity of amino groups with epoxy groups, primary amines have two NH equivalents and thus bonding sites with epoxides. In this way, compound XR can be bonded to a side chain position of the molecule. The overall result of this is in turn beneficial to the sandability of the surface primer layer.

[0051] The R group is an organic group containing a polyoxyalkylene unit, particularly preferably a polyethylene or polypropylene unit or a mixed polyethylene / polypropylene unit. Preferably, the organic R group is composed of a polyoxyalkylene unit in addition to any molecular unit obtained by synthesis. For simplicity, the R group is also referred to as a polyoxyalkylene. The molecular unit obtained by synthesis is, for example, an organic group of a molecule used when the polyoxyalkylene chain is initially formed, for example, by means of a starting alcohol for initiating the polymerization of ethylene oxide and / or propylene oxide. Preferably, the R group is polyethylene, polypropylene or a mixed polyethylene / polypropylene.

[0052] The weight average molecular weight of compound (Ia2) can vary within wide ranges, for example from 800 to 2200 g / mol (determined by size exclusion chromatography combined with light scattering).

[0053] The compounds XR can be prepared in-house or obtained commercially. For example, the apparently preferred polyoxyalkylene monoamines are available from Huntsman under the trade name "Jeffamine".

[0054] The epoxy-functional resin mixture (Ia) contains two components (Ia1) and (Ia2) in a mutually reactive form. Thus, the epoxy groups of component (Ia1) and the X groups of component (Ia2) react with each other. The corresponding reaction schemes and conditions are known to the person skilled in the art and do not require any further mention.

[0055] Component (Ia) is an epoxy-functional resin mixture. Therefore, it is obvious from the raw materials that components (Ia1) and (Ia2) are used in such a way that the epoxy groups of component (Ia1) are in excess relative to the reactive unit molar stoichiometry of the X group. The number of reactive units refers to the number of potential attachment sites for each epoxy group. For hydroxyl or secondary amino groups, for example, there is one reactive unit for each X group. For primary amino groups, there are two reactive units (two NH functional groups). Preferably, the molar ratio of the epoxy reactive units of the epoxy groups of compound (Ia1) and the X groups of component (Ia2) is 10-1.1, more preferably 5-1.5, and particularly preferably 3.5-1.8.

[0056] The amount of epoxy groups in component (Ia1) can be obtained or appropriately adjusted in a known manner according to the purpose by determining the epoxy equivalent. The amount of reactive units in the X group is obtained by test methods known per se for determining the amount of X functional groups, for example by determining the amine value, OH value or acid value (DIN 53176: 2002-11, DIN 53240-3: 2016-03, DIN EN ISO 2114 correction 1: 2006-11).

[0057] Component (Ia) preferably has an epoxy equivalent weight of 500 to 1500 g / mol, more preferably 600 to 1200 g / mol.

[0058] The component (Ib) which reacts with the component (Ia) comprises at least one di- and / or polyfunctional monomeric primary and / or secondary amine (M). Preferably, the component (Ib) consists of at least one such amine (M).

[0059] Examples of suitable amines (M) have already been described above as constituents of the resin component (R). All statements and preferred variants made there apply correspondingly to the amines in component (Ib).

[0060] Resin mixture (I) is an amino-functional resin mixture, so its preparation requires an excess of NH equivalents relative to the functional group molar of components (Ia) and (Ib) to be reacted with each other. In particular, the NH equivalent of resin mixture (I) is 50-140g / mol, preferably 70-130g / mol (determination method see the embodiment part). In addition, resin mixture (I) contains 17.5-40% by weight, preferably 25-35% by weight of di- and / or multifunctional monomer primary amine and / or secondary amine (M), i.e. component (Ib). Both of these standards can be adjusted by those skilled in the art by appropriately selecting the molar amount of the two components and the knowledge of the quantitative conversion of epoxy and NH functional groups under conditions and reaction schemes known per se. In addition, the examples below give a more specific overview again. Possible reaction schemes and corresponding conditions are known to those skilled in the art and do not require any further mention. Preferably, resin mixture (I) is dispersed in water after its preparation, and in this case is an aqueous dispersion.

[0061] The resin mixture (I) can be prepared as described above and is thus obtained in the form of an aqueous dispersion. Aqueous dispersions of the resin mixture (I) are likewise commercially available (for example as Beckopox VEH 2849w / 80 WA (from Allenex)).

[0062] Step B

[0063] In the second step (B) of the reaction sequence, the two starting components (IIa) and (IIb) are reacted with one another in the aqueous phase, i.e. component (IIa) contains the amino-functional resin mixture (I) and component (IIb) contains at least one di- and / or polyfunctional organic epoxy compound with an average epoxy equivalent weight of less than 400 g / mol, preferably less than 350 g / mol, more preferably less than 250 g / mol. This produces, optionally after removal of the organic solvent used, an aqueous dispersion (AD) comprising the resin component (R). It is evident from the properties of the resin component (R) already mentioned in detail above that the amounts of components (IIa) and (IIb) are matched to one another so that the NH equivalents of component (IIa) are in molar excess relative to the epoxy groups of component (IIb).

[0064] Preference is given to using the direct reaction product of step (A) as component (IIa), which is only optionally supplemented with solvents or auxiliaries such as emulsifiers. This is because the resin mixture (I) is obtained as an aqueous dispersion after step (A) and can therefore be used directly in step (B) carried out in the aqueous phase. Component (IIa) preferably does not contain any other ingredients that can react with component (IIb) other than the reaction product.

[0065] Component (IIb) preferably consists of at least one, preferably exactly one, di- and / or polyfunctional organic epoxy compound, the epoxy equivalent of which satisfies the above-mentioned prerequisites. Examples of suitable epoxy compounds are those already described above as component (Ia1). All the statements made there and the preferred variants apply accordingly to the epoxy compound in component (IIb).

[0066] The solids content of the aqueous dispersion (AD) is, for example, 25 to 45% by weight (for test methods, see the Examples section).

[0067] Preparation method of aqueous dispersion (AD)

[0068] The above description obviously also leads to a process for preparing the aqueous dispersion (AD). All essential and preferred features of the process variants described above obviously also apply to this preparation process.

[0069] Waterborne two-component (2K) coating compositions

[0070] The aqueous coating composition of the present invention is a two-component coating composition.

[0071] As is known, the 2K composition is understood to mean that component (1) (coat base component), which is defined in more detail further below, and component (2) (curing component), which is defined below, are prepared and stored separately from one another and are not combined until shortly before application. The processing time or pot life, i.e. the time during which the coating composition can be processed at room temperature (15-25° C., in particular 20° C.) without an increase in viscosity, which is due to the corresponding crosslinking reaction at room temperature being, for example, so vigorous that application is no longer possible, depends, as is known, on the ingredients used in components (1) and (2). In the context of the present invention, the processing time of the coating composition is preferably at least 2 minutes to 60 minutes, more preferably at least 5 minutes to 60 minutes. A particular advantage of the two-component coating composition is that, in particular, no high temperatures are required for curing. Preferably, after application to the substrate, the coating composition of the invention is cured at not more than 80° C., particularly preferably not more than 65° C.

[0072] Curing refers to a process known to the person skilled in the art, in other words, the conversion of a coating composition applied as a film to a substrate into a ready-to-use state, in other words, into a state in which the substrate provided with the coating can be put into its intended use. As regards the problem which is also relevant to recoating and which has been solved in the context of the present invention, namely the achievement of good sandability, specifically sandability and subsequent overcoatability are of course criteria for the intended use. Curing is achieved in particular by chemical reaction of reactive functional groups of the binder components present in the different components (1) and (2) of the coating composition. In the context of the present invention, therefore, particular mention should be made of the reaction of the amino or NH functional groups of the polyamine component in the polyamine-based curing component (2) with the epoxy groups of the at least one epoxy resin (E) in the binder component (I) of the 2K coating composition of the invention. As a result of these crosslinking reactions and the parallel evaporation of any organic solvent and / or water present, a coating film is formed, i.e. a cured coating (cured coating) is produced. Activation of the reaction can be achieved by thermal energy, although in the case of the present invention there is the above-mentioned advantage that high temperatures are not required.

[0073] The term "binder" or "binder component" in this context refers to the non-volatile matter of the coating material, excluding pigments and fillers, according to the relevant DIN EN ISO 4618. In this context, specific binder components include, in addition to the epoxy resin (E), the polyamine components or coating additives already mentioned above.

[0074] However, purely for the sake of clarity, the term "binder" is used primarily in connection with the resin component of the base component (1), i.e. in particular the epoxy resin (E), which is responsible for film formation, whereas the polyamine component present in the curing component (2) is primarily referred to as a curing agent or crosslinker.

[0075] It is also known that, in addition to binders and solvents, the binder component (1) generally also contains all or most of the other functional ingredients of the composition, such as pigments, fillers and additives, whereas the curing component (2) contains, in addition to solvents and any additives present, only the components intended for crosslinking. The terms "binder component" and "curing component" in connection with 2K coating compositions are known to the person skilled in the art and also have essential and therefore delimiting characteristics within a certain structural range. In the context of the present invention, it is important that the binder component contains pigments and fillers, preferably all pigments and fillers used in the corresponding coating composition.

[0076] Of course, in order to complete the 2K coating composition, at least one further main component may also be present. This means that, in addition to the base component (1) and the curing component (2), further ingredients such as solvents or additives may be added to the at least one further main component, for example after the two main components (1) and (2) have been added. However, by definition, the composition is still a 2K coating composition, since the number of components containing the components that are responsible for film formation and that crosslink with each other is two.

[0077] 2K coating compositions have excellent suitability as surfacer and primer-surfacer and can be used directly. Therefore, the 2K coating composition is preferably a surfacer or primer-surfacer. The functions, structures and application areas of surfacer and primer-surfacer are in principle known to the person skilled in the art and have delimiting features in this respect. In the case of automotive OEM finishing, the surfacer is usually applied as an intermediate layer (applied to the previously cured electrophoretic coating), cured separately and then overcoated with a basecoat and a clearcoat. Primers and surfacers are used in particular in the automotive recoat sector, where they are responsible for filling in locally damaged areas in the initial paint system and for achieving suitable adhesion on the substrate and ensuring corrosion protection.

[0078] The 2K coating composition comprises an epoxy resin-based binder component comprising an aqueous dispersion of at least one pigment (P) and / or filler (F) in at least one epoxy resin (E). The binder component can of course also consist of the dispersion.

[0079] In principle, it is known that pigments and fillers are used in coating compositions in the form of dispersions. This means that the preparation of the coating composition includes a step in which the pigment or filler is dispersed and thus converted into a dispersion by introducing a resin and a common solvent such as water into a grinder or dissolver under high shear forces. The resin here has a dispersing or emulsifying effect and only promotes the stabilization of the pigment or filler. In order to further assist the dispersion, other additives can of course also be used. It is also possible that the preparation of the dispersion includes adding all the paint ingredients to be introduced into the paint base component, so that the paint base component is therefore ultimately composed of the dispersion.

[0080] Thus, a dispersion is a mixture containing at least (but not necessarily exclusively) a resin and a pigment and / or a filler in dispersed form with respect to one another.

[0081] In the context of the present invention, the dispersion must contain a specific epoxy resin as a resin component for the dispersion. Only in this way is a 2K coating composition obtained which, in addition to the properties to be achieved in principle, such as adhesion and corrosion protection, after application and curing, also enables a coating without visual defects such as holes to be obtained. More particularly, it has been found that the dispersion operation carried out in a polyamine component as in the prior art does not lead to this excellent optical quality. Even more surprisingly, the object can only be achieved with a specific epoxy resin (E). This is because from a technical point of view, it is completely impossible to prepare dispersions in different epoxy resins, because the mixture to be dispersed undergoes irreversible thickening or curing due to rheological degradation, making the preparation of the coating composition no longer possible, or the degradation process does allow the formulation of a paint, but a paint with very poor properties after application and curing. In addition, in this case, the cleaning of the dispersion unit is extremely difficult, so that the method is not industrially applicable.

[0082] The fact that the binder component contains a dispersion or consists of a dispersion therefore means that either the dispersion is prepared as described above and then completed with further paint ingredients that are not yet present to prepare the binder component (for example using standard stirring equipment) or, in the case of preparation of a dispersion, all ingredients of the binder component are introduced into the dispersing process and the dispersion therefore constitutes the binder component.

[0083] The fact that the dispersion is aqueous means of course that it contains water as solvent and preferably, water is also used in the actual dispersing process. The exact definition of "aqueous" can be found above.

[0084] Preferably, the dispersion contains all the pigments and / or fillers used in the coating composition. Also preferably, the dispersion contains no other epoxy resins besides the at least one epoxy resin (E). Again preferably, the epoxy resin (E) accounts for at least 90% by weight, preferably at least 95% by weight, of the binder component of the dispersion. The binder component is obtained by subtracting the proportion of pigments and fillers from the solids (non-volatile components) of the dispersion.

[0085] The 2K coating composition contains at least one specific epoxy resin (E) in the binder component (1) or in an aqueous dispersion. The binder component (1) and therefore the coating composition of the invention preferably do not contain any other epoxy resins other than the epoxy resin (E). The epoxy groups can react with the NH functional groups of the polyamine components present in the curing component (2) after mixing the two main components (1) and (2), thereby forming a network structure and in this way contributing to the curing of the coating produced from the coating composition.

[0086] Epoxy resins are known in principle and have also been described above in connection with components (Ia1) and (IIb). These are therefore polycondensation resins which contain, on statistical average, more than one epoxy group in the base molecule. These are, for example, epoxy resins which are prepared by condensation of bisphenol A or bisphenol F with epichlorohydrin. These compounds contain hydroxyl groups along the chain and epoxy groups at the ends. Corresponding epoxy resins are commercially available, for example, as 100% systems or solutions / dispersions in organic solvents or water.

[0087] With respect to the epoxy resin (E), particular important features essential to the present invention should be noted.

[0088] It is essential for the present invention that the epoxy resin (E) has:

[0089] (i) a maximum sedimentation rate not exceeding 17,500 μm / h (measured in an optical cuvette centrifuge at an acceleration of 2050 g, diluted to 30% solids with water) and a glass transition temperature less than 0°C (measured by dynamic differential calorimetry, heating rate 10 K / min, run 2), or

[0090] (ii) a maximum sedimentation rate of at least 12500 microns / hour and a glass transition temperature of at least 0°C.

[0091] Surprisingly, only through this combination of properties, by means of the above-described dispersing operation, can a binder component (1) and ultimately also a coating composition be provided which combines the properties described with one another and leads in particular to very good optical quality of the coatings produced therefrom, which do not contain any surface defects such as pores.

[0092] In a preferred embodiment, the epoxy resin has:

[0093] (i) a maximum sedimentation rate of 2500 to 17500 microns per hour and a glass transition temperature of -30°C to less than 0°C, or

[0094] (ii) Maximum sedimentation rate of 12500-30000 microns / hour and glass transition temperature of 0-20°C.

[0095] Particularly preferred variants are described below:

[0096] 10000-17500 microns / hour maximum sedimentation rate and -30℃ to -10℃ glass transition temperature,

[0097] Maximum sedimentation rate of 10000-17500 microns / hour and glass transition temperature of 0-20°C.

[0098] Preferably, the epoxy equivalent of the epoxy resin (E) is less than 500 g / mol, preferably less than 350 g / mol, more preferably less than 300 g / mol, and particularly preferably less than 250 g / mol (for the test method, see the Examples section). The preferred range is 100-500 g / mol, more preferably 150-250 g / mol.

[0099] Preferably, the epoxy resin is used in the form of an aqueous dispersion which optionally additionally contains a small proportion of organic cosolvents. Such epoxy resin dispersions are commercially available, for example (see also the Examples).

[0100] The proportion of the at least one epoxy resin (E) is, for example, 15 to 40% by weight, more preferably 20 to 30% by weight, based on the solids content of the coating composition. If the at least one epoxy resin is used in the form of a dispersion, the amount of dispersion is adjusted, for example, taking into account the solids of the dispersion, depending on the desired amount of resin.

[0101] The 2K coating composition contains as an essential ingredient a polyamine-based curing component (2), i.e. a curing component containing a polyamine component. In principle, such polyamine components and their use in epoxy / amine 2K coating compositions are known. These are mixtures of polymeric and optionally monomeric polyamines which contain primary and / or secondary amino groups and which can participate in crosslinking reactions via the correspondingly present NH functions with the epoxy groups of the likewise present epoxy resins, here at least the epoxy resin (E) .

[0102] The polyamine component has, for example, an NH equivalent weight of 50-500 g / mol, preferably 100-400 g / mol, more preferably 150-300 g / mol (for the determination method, see the Examples section).

[0103] In principle, any polyamine component known to the person skilled in the art in this regard can be used in the context of the present invention. In a variant of the invention which is not essential to the invention but is preferred, a specific polyamine component described in more detail below is used in the curing component (2), i.e. the resin component (R) present in the aqueous dispersion (AD).

[0104] Preferably, the molar ratio of the NH functional groups of the polyamine component in the resin component (2) to the epoxy groups of the epoxy resin in the binder component (1) is 0.7:1 to 0.95:1, for example 0.9:1.

[0105] 2K coating compositions are aqueous, ie contain at least water as solvent. The exact definition of "aqueous" can already be found above.

[0106] Furthermore, 2K coating compositions contain pigments and / or fillers.

[0107] Preferred pigment is black and / or white pigment.Therefore, priming paint preferably contains at least one black pigment or at least one white pigment or at least one white pigment and a black pigment.This means that priming paint of the present invention preferably has black, white or (various grayscales) gray.Certainly, it is not impossible to have other pigments.

[0108] Preferred black pigments are typical organic and inorganic black pigments, especially inorganic black pigments, such as are commercially available in powder form. Particular mention should be made of pigment black (carbon black), iron oxide (Fe3O4) pigments such as typical synthetic iron oxides (available, for example, under the trade name Bayferrox from Lanxess), mixed oxide pigments such as manganese black or spinel black. Very particular preference is given to pigment black (carbon black) and iron oxide pigments.

[0109] Preferred white pigments are typical inorganic white pigments, such as titanium dioxide (eg the rutile pigment known from Kronos under the Kronos trade name), zinc oxide, zinc sulfide or antimony trioxide. Very particular preference is given to titanium dioxide, especially in its rutile modification.

[0110] Further preferred pigments are those known by the umbrella term "anticorrosion pigments". Zinc phosphate is particularly preferred here. Although zinc phosphate has a white color, it is not classified as a white pigment but as an anticorrosion pigment due to its anticorrosion effect.

[0111] The proportion of the pigments is preferably from 15 to 25% by weight, in particular 20% by weight, based in each case on the solids content of the coating composition.

[0112] The fillers preferably present are all inorganic and organic fillers known per se and well known to the person skilled in the art, preferably inorganic fillers. Thus, fillers include in particular substances known to the person skilled in the art, which are used, for example, in particulate form or in powder form to obtain specific physical properties of the coating composition and which are insoluble in the corresponding medium of use. These include in particular carbonates such as calcium carbonate or barium carbonate, sulfates such as calcium sulfate and barium sulfate, silicates and phyllosilicates such as talc, pyrophyllite, mica, kaolin, precipitated calcium silicate, aluminum silicate, calcium / aluminum silicate, sodium / aluminum silicate and mullite, silicon dioxide such as quartz, cristobalite, precipitated silicon dioxide or in particular pyrogenic silicon dioxide obtainable, for example, under the trade name Aerosil (from Evonik), metal oxides and hydroxides, for example aluminum hydroxide and magnesium hydroxide.

[0113] The proportion of fillers is preferably from 30 to 50% by weight, in particular from 30 to 40% by weight, in each case based on the solids content of the coating composition.

[0114] In addition, the coating composition may also contain at least one additive. Examples of such additives are light stabilizers, antioxidants, degassing agents, emulsifiers, slip additives, polymerization inhibitors, tackifiers, leveling agents, film-forming aids, thickeners, sag regulators (SCA) or corrosion inhibitors. They are used in conventional and known amounts. The same applies to possible use of organic solvents, but their amounts are selected so that they do not change the aqueous character of the coating composition.

[0115] The solids content of the 2K coating composition can vary depending on the requirements of the individual case, but is preferably 70-85% by weight. The solids content is primarily determined by the viscosity required for application, more particularly spray application, and can therefore be adjusted by a person skilled in the art based on his or her general technical knowledge, optionally with the aid of some exploratory tests.

[0116] The 2K coating composition can be prepared using conventional and known mixing methods and mixing devices for preparing coating compositions, for example stirred tanks, stirred mills, extruders, kneaders, Ultraturrax, inline dissolvers, static mixers, toothed ring dispersers, expansion nozzles and / or microfluidizers. Of course, it should be noted that component (1) (binder component) and component (2) (curing component) are prepared and stored separately from one another and, as described above, are only combined and mixed shortly before the coating composition is applied to the substrate. It should also be ensured that the binder component (1) contains or consists of the above-mentioned dispersion. This means that the preparation of the 2K coating composition includes at least the preparation of this dispersion.

[0117] The present invention further provides a method for preparing a coating on a substrate, wherein the coating composition of the present invention is applied to the substrate and then a coating film is formed. It should be understood that in the context of the method of the present invention using the coating composition, the above-mentioned specific and preferred embodiments of the coating composition are equally applicable.

[0118] The coating composition of the invention can be applied to the substrate in particular in the layer thicknesses customary in the automotive industry, for example 5 to 200 micrometers, preferably 10 to 150 micrometers, more preferably 30 to 70 micrometers. The layer thickness is to be regarded as the dry film layer thickness after curing described below. For example, known methods are used here, such as spraying, knife coating, painting, pouring, dipping, immersion, dripping or roller coating. Preferably, a spraying method is used.

[0119] After applying the composition of the present invention, a polymer film or a cured coating film is formed therefrom. Therefore, the applied composition is cured by known methods. Curing is carried out at a temperature of, for example, 15-120° C., in particular 20-80° C., most preferably 20-65° C. These preferred relatively low curing temperatures are especially due to the fact that the coating composition is a (2K) coating composition, in which case, especially thermal crosslinking only requires a low curing temperature. The curing time can vary significantly in various cases, for example, from 5 minutes to 16 hours, preferably 20-80 minutes. These preferred relatively short curing times are especially due to the fact that the composition of the present invention only requires a relatively short curing time at still relatively low temperatures in order to have sufficient hardness to enable sanding of the cured coating. In this regard, a very particularly preferred curing operation is carried out at 40-65° C. for 20-80 minutes.

[0120] In each case, curing can optionally be carried out by flashing, for example, at room temperature (about 15 and 25° C.), for example for 1 to 60 minutes. For the purposes of the present invention, flashing refers to the evaporation of organic solvents and / or water, whereby the coating dries but is not yet fully cured, and in particular, a fully crosslinked paint film is not formed.

[0121] Curing then provides the coated substrate of the invention, which likewise forms part of the subject matter of the present invention. The invention also provides a coating produced from the composition.

[0122] Substrates used are, for example, metal substrates, preferably those used in the automotive industry (vehicle construction). Advantageously, unalloyed and alloyed steels and / or iron, zinc and aluminum substrates and the corresponding alloys are used.

[0123] If it is stated above that the composition is applied to a substrate, this does not, however, necessarily mean that the composition must be applied directly to a metal substrate. On the contrary, there may be at least one further layer between the metal substrate and the layer formed by the composition. This is the case, for example, when the coating composition is used as a surfacer in OEM finishing. This is because in this case there is at least one electrophoretic coating between the surfacer layer and the metal substrate. In other words, the substrate to which the composition of the invention is applied is therefore a metal substrate coated with an electrophoretic coating.

[0124] However, as already mentioned above, the coating compositions of the invention are particularly advantageously used as primer-surfacer in the recoating sector, in particular in the automotive recoating sector, and in this case, after only a short curing period at moderate temperatures, have properties such as good adhesion, corrosion protection and sandability.

[0125] Therefore, in a particular embodiment of the present invention, the substrate is a metal substrate that has been completely painted, especially those painted with a multi-layer automotive paint system, wherein the corresponding multi-layer coating has local damage (defects). More particularly, these are automobile bodies or parts thereof with damage such as stone chip damage, etc. In the damaged area, the initial multi-layer coating has therefore been at least partially peeled off due to external effects. Then, the coating composition of the present invention is used as a first-surface mixed primer for the repair of these damaged areas, i.e., recoating. Usually, in the recoating operation, before applying the primer, the damaged initial coating substrate is cleaned and sanded. This removes any only insufficiently adhered and partially peeled areas and / or corrosion products that have been formed of the initial coating present, and especially also locally exposes the metal substrate. Therefore, this is a complex substrate surface with a wide range of different interfaces. Here, one interface is the interface with the fully exposed metal substrate. Other interfaces and edges can be found in the areas between the damaged, cleaned and sanded parts and in the areas around these parts with a complete initial paint system. At all these interfaces, one and the same coating composition must ensure sufficient adhesion. The composition of the present invention therefore offers great advantages since even in such demanding areas, excellent adhesion, corrosion resistance and sanding properties are achieved.

[0126] In a preferred embodiment of the invention, after the cured coating, especially the surfacer or the primer-surfacer layer, is prepared from the composition of the invention, further coating compositions are applied and a multi-coat paint system is formed. These further coating compositions are especially standard basecoats and clearcoats.

[0127] The present invention will be explained below by way of examples. Example

[0128] Determination method

[0129] The proportion of monomer amine in aqueous dispersion

[0130] The determination is carried out by gas chromatography in accordance with DIN 51 405:

[0131] The samples were directly injected into a split injector of a gas chromatograph with a flame ionization detector and separated on a column with a polar phase (polyethylene glycol; 50 m fused silica capillary column with polyethylene glycol phase) and a non-polar column (polydimethylsiloxane; 50 m fused silica capillary column with polydimethylsiloxane phase). Evaluation was performed by the ISTD% method.

[0132] On an analytical balance, weigh approximately 100-500 mg of sample (depending on the amine content) accurately to 0.1 mg into a 5 mL snap-top vial. Weigh approximately 5% ISTD diglyme accurately to 0.1 mg into the sample. Dilute the sample with 5 mL of THF. (If the sample does not dissolve in THF, you must experiment to find a suitable solvent.)

[0133] The samples thus prepared were analyzed on an Agilent 7890 gas chromatograph. Injections were performed by autosampler.

[0134] Gas chromatography conditions:

[0135] Oven program: 40℃ (holding time 5 minutes) (3℃ / minute) → 100℃ (10℃ / minute) → 230℃ (holding time 5 minutes)

[0136] Carrier gas: Hydrogen

[0137] Separation column: Agilent Innowax: length 50 m, membrane thickness 0.2 μm, diameter 0.2 mm, pressure 1.0 bar HP-1, length 50 m, membrane thickness 0.33 μm, diameter 0.2 mm, pressure 1.3 bar

[0138] Injector temperature: 250°C (lower if necessary)

[0139] Injection volume: 0.3μL (manual injection 0.3-0.6μL)

[0140] Detector: Flame ionization detector

[0141] Detector temperature: 275°C

[0142] Split flow: 15mL / min

[0143] The amines are identified by their retention times on polar and nonpolar columns (see comparative chromatograms). For unknown components, GC / MS analysis is necessary.

[0144] The amines to be tested and the internal standard are weighed accurately to 0.1 mg on an analytical balance, according to the approximate proportion in the sample. The amine concentration in the total calibration solution corresponds to the amine concentration in the prepared sample (the concentration of the amine is calculated by the GC analyzer program). Subsequently, the calibration solution is analyzed under the same conditions as the samples and the substance-specific correction factor is determined.

[0145] The amine content of the samples was calculated by the ISTD% method with the aid of the GC analyzer program.

[0146] Epoxy equivalent

[0147] The determination was carried out in accordance with DIN EN ISO 3001.

[0148] Solid content (non-volatile matter)

[0149] Unless otherwise stated, the solids content (also called solids fraction, solids content, non-volatile fraction) is determined in accordance with DIN EN ISO 3251 at 130° C.; 60 minutes, starting weight 1.0 g.

[0150] Proportion of polymerized organic amine (polyamine) in aqueous dispersion

[0151] The determination is carried out analogously to the determination of the solids content, except that the sample is kept at 130° C. for 8 hours (instead of 60 minutes). In this way, it is ensured that any residual proportion of non-volatile monomeric amine (M) is negligibly small and that the measurement result corresponds to the parameters assigned to this result.

[0152] Ratio of the resin mixture (I) or the resin components in the aqueous dispersion

[0153] This ratio results from the sum of the monomeric amine ratio and the polyamine ratio in the aqueous dispersion.

[0154] The proportion of monomeric amines or polyamines in the resin mixture (I) or the resin component (R)

[0155] The proportion of monomeric amines in the resin mixture (I) or the resin component (R) is obtained by dividing the proportion of monomeric amines in the aqueous dispersion by the sum of the proportion of monomeric amines and the proportion of polyamines in the aqueous dispersion. The proportion of polyamines is determined in a corresponding manner.

[0156] NH equivalent

[0157] The NH equivalent of the resin component (R) and the resin mixture (I) is determined in the following continuous manner.

[0158] a)

[0159] First, the NH equivalent weight of the resin mixture (I) present in the aqueous dispersion is determined. For this purpose, firstly, the different mass ratios of primary and secondary amino groups in the aqueous dispersion (each in % nitrogen) are determined by the method according to DIN EN ISO 9702 (October 1998) by means of aliphatic amines. The mass ratios obtained are then used to obtain the molar amount of NH functional groups in 100 g of aqueous dispersion by the following calculation:

[0160] n(NH)=(m(N of primary amino group) / (14 g / mol))*2+m(N of secondary amino group) / (14 g / mol)

[0161] (where "m" denotes the mass ratio measured in each case).

[0162] The molar amount of NH functional groups and the mass of the sample (100 g) ultimately lead to the NH equivalent weight of the sample (aqueous dispersion), ie the mass of the sample in which 1 mol of NH functional groups is present.

[0163] By determining the ratio of the resin mixture of the sample, the NH equivalent weight of the resin mixture (I) can then be calculated:

[0164] (NH equivalent (resin mixture (I)) = NH equivalent (sample) * ratio (resin mixture in sample))

[0165] The proportion of the resin mixture in the sample is expressed as the sum of the proportion of the polyamine and the proportion of the monomeric amine (see above).

[0166] b)

[0167] Then, the NH equivalent of the resin component (R) is calculated from the previously determined NH equivalent of the resin mixture (I), the mass of the resin mixture (I) used in step (B), the mass of the component (IIb) used in step (II) and the molar amount of the epoxy groups used in the component (IIb) (determined by the mass of the component (IIb) used and the epoxy equivalent). This assumes that the epoxy groups react quantitatively with the NH functional groups. The total mass of the resin component (R) is obtained by adding the mass of the resin mixture (I) used and the mass of the component (IIb) used.

[0168] Determination of the storage stability of paint binders

[0169] According to DIN 532111 (1987-06-00), the flow time (seconds) of a ready-to-use primer-surfacer (binder, curing agent and water) is determined with a DIN No. 4 cup. The flow time is determined again 30 minutes after the components have been mixed and 60 minutes after the components have been mixed. The three values ​​(seconds) are measured on freshly prepared materials (no earlier than 24 hours after the preparation of the binder in the bead mill and from the mixing of the curing components). Subsequently, the binder samples are stored at 40° C. and after 8 weeks, the flow time of the finished surface primer is measured again and after 30 and 60 minutes. For this purpose, fresh curing agent samples are prepared, because the storage stability of the binder is to be tested. If the flow time value of the ready-to-use sample consisting of fresh binder and fresh curing agent differs by less than 5 seconds from the flow time value of the ready-to-use sample of aged binder and fresh curing agent, the binder is classified as storage-stable.

[0170] Glass transition temperature

[0171] In the context of the present invention, the glass transition temperature Tg is experimentally determined using a method based on DIN 51005 "Thermal Analysis (TA)-Terms" and DIN 53765 "Thermal Analysis-Dynamic Scanning Calibratorimetry (DSC)". Here, 10 mg of sample is weighed into a sample boat and inserted into the DSC instrument. Cooling to the starting temperature is followed by the 1st and 2nd rounds of measurement, purging with 50 mL / min of inert gas (N2), a heating rate of 10 K / min, and cooling back to the starting temperature between the two rounds of measurement. The measurement is usually carried out in a temperature range of about 50°C below the expected glass transition temperature to about 50°C above the glass transition temperature. In the context of the present invention and according to DIN 53765, Section 8.1, the glass transition temperature is the temperature at which the change in specific heat capacity reaches half (0.5Δcp) in the 2nd round of measurement. It is determined from a DSC graph (heat flow versus temperature curve) and is the temperature of the intersection of the midline between the extrapolated baselines before and after the glass transition with the measured curve.

[0172] Maximum sedimentation rate

[0173] This method is used to characterize the sedimentation process of dispersed materials. To this end, the sample is accelerated in an optical cuvette centrifuge and is therefore subjected to centrifugal forces. The effect is to separate the dispersed sample components according to their density. The separation method can be performed along the cuvette as a function of time. The resulting rate curve characterizes the mechanism of sedimentation (when the density of the dispersed particles is greater than the density of the surrounding dispersant) or emulsification (when the density of the dispersed particles is less than the density of the surrounding dispersant).

[0174] In the case of sedimentation, the rate at which the phase boundary between the sediment and the clarified supernatant changes position can be used as a quantification of the sedimentation process: a sample whose phase boundary barely changes position over a given time has much greater sedimentation stability than a sample whose phase boundary undergoes significant movement over the same period of time.

[0175] Since before starting the measurement the sample is still not subjected to any centrifugal forces and the homogeneity of the sample is at the maximum possible level, the sedimentation rate will be at its highest level at the beginning or at least during the initial period of the measurement and then gradually decrease.

[0176] The actual measurement is carried out as follows: First, the epoxy resin sample to be analyzed is adjusted to a solid content of 30% with water. The sedimentation rate of the sample in 6 hours is then analyzed in an optical cuvette centrifuge (LUMiSizer 651), and the maximum sedimentation rate in this time period is evaluated (PA cuvette, optical path length 2mm, measuring temperature 25°C, wavelength 870nm, 2050g). Experience shows that the maximum sedimentation rate occurs within the first 0.5-1.5 hours, and sedimentation almost or completely stops after 4-6 hours.

[0177] Polyamine component for coating composition

[0178] Aqueous dispersion (AD1)

[0179] 683.00 g of Beckopox VEH 2849W (aqueous dispersion of resin mixture (I), wherein the resin mixture contains 27.5% by weight of monomeric amines (isophoronediamine and xylylenediamine) and 72.5% by weight of polyamines and furthermore has an NH equivalent of 108 g / mol) and 1663.77 g of demineralized water are combined in a reaction vessel, stirred continuously and kept at 95° C. for 1 hour. Subsequently, the mixture is cooled to 70° C., 163.44 g of a mixture of bisphenol A diglycidyl ether epoxy resin having an average epoxy equivalent of 186.5 g / mol, 39.46 g of a polyalkylene polyether epoxide based on polyoxypropylene having an average epoxy equivalent of 395 g / mol, and 81.96 g of ethoxypropanol are added; 81.47 g of methyl ethyl ketone and 81.72 g of isobutanol are metered in continuously over a period of 4 hours with stirring, and the mixture is kept at 70° C. for a further hour. The reaction product thus obtained was cooled to 45° C. The viscosity of the product at 25° C. was 150-250 mPas.

[0180] In a subsequent process step, the process solvents isobutanol and methyl ethyl ketone were removed from the product by distillation under reduced pressure. The residual isobutanol and methyl ethyl ketone contents of the resulting aqueous dispersion (AD1) were <0.5% (gas chromatography).

[0181] The resin component (R) content in the aqueous dispersion was 33.4 wt% (2.4 wt% monomeric amine, 31% polyamine). Therefore, the resin component had a monomeric amine (M) content of 7.2 wt%. In addition, the resin component had an amine equivalent (NH equivalent) of 171 g / mol.

[0182] Aqueous dispersion (AD2)

[0183] 683.00 g of Beckopox VEH 2849W (aqueous dispersion of resin mixture (I), wherein the resin mixture contains 27.5% by weight of monomeric amines (isophoronediamine and xylylenediamine) and 72.5% by weight of polyamines and furthermore has an NH equivalent of 108 g / mol), 266.11 g of methyl ethyl ketone and 1395.96 g of (demineralized) water are combined in a reaction vessel, stirred continuously and kept at 70° C. for 1 hour. Subsequently, a mixture of 163.44 g of bisphenol A diglycidyl ether epoxy resin having an average epoxy equivalent of 186.5 g / mol, 39.46 g of polyalkylene polyether epoxide based on polypropylene oxide having an average epoxy equivalent of 395 g / mol, and 81.96 g of ethoxypropanol is added; 81.47 g of methyl ethyl ketone and 81.72 g of isobutanol are metered in continuously over a period of 4 hours with stirring, and the mixture is kept at 70° C. for a further hour. The reaction product thus obtained was cooled to 45° C. The viscosity of the product at 25° C. was 150-250 mPas.

[0184] In a subsequent process step, the process solvents isobutanol and methyl ethyl ketone were removed from the product by distillation under reduced pressure. The resulting aqueous dispersion (AD2) had a residual content of isobutanol and methyl ethyl ketone of <0.5% (gas chromatography).

[0185] The resin component (R) content in the aqueous dispersion was 33 wt% (2.4 wt% monomeric amine, 31% polyamine). Therefore, the resin component had a monomeric amine (M) content of 7.2 wt%. In addition, the resin component had an amine equivalent (NH equivalent) of 171 g / mol.

[0186] Aqueous dispersion (AD3)

[0187] Step (A)

[0188] 1000 g of a polyalkylene polyether monoamine based on propylene oxide / ethylene oxide (Jeffamine M2070, primary amine functional groups (=2 NH functional groups)) with an average molecular weight of 2000 g / mol and 448.8 g of a bisphenol A diglycidyl ether-based epoxy resin with an average epoxy equivalent of 186.5 g / mol were mixed in a reaction vessel, and the internal temperature was then maintained at 130° C. for 1 hour and at 80-90° C. for another 2 hours. The epoxy equivalent of the product thus obtained was 1035 g / mol. The viscosity of the product was 6734 mPas at 23° C.

[0189] 96.43 g of the reaction product thus obtained were mixed with 33.9 g of isophorone diamine and 27.12 g of meta-xylylenediamine in a reaction vessel, and the internal temperature was then kept at 60° C. for 1 hour and at 80-90° C. for another 2 hours. After cooling to 50° C., dilution with water (solids content 80%) was carried out. The resin mixture (I) present in the dispersion had an amine equivalent (NH equivalent) of 105 g / mol. The viscosity of the product was 1540 mPas at 23° C.

[0190] Step (B)

[0191] 683.00 g of the reaction product of step (A) and 1663.768 g of (demineralized) water were combined in a reaction vessel, stirred continuously and kept at 95° C. for 1 hour. Subsequently, the mixture was cooled to 70° C., 163.44 g of a mixture of bisphenol A diglycidyl ether epoxy resin having an average epoxy equivalent of 186.5 g / mol, 39.46 g of a polyoxypropylene-based polyalkylene polyether epoxide having an average epoxy equivalent of 395 g / mol, 81.96 g of ethoxypropanol were added; 81.47 g of methyl ethyl ketone and 81.72 g of isobutyl alcohol were metered in continuously over a period of 4 hours with stirring, and the mixture was kept at about 70° C. for a further hour. The reaction product thus obtained was cooled to 45° C. The viscosity of the product was 150-250 mPas at 25° C.

[0192] In the subsequent process step, the process solvents isobutanol and methyl ethyl ketone were removed from the product by distillation under reduced pressure. The residual isobutanol and methyl ethyl ketone content of the resulting aqueous dispersion (AD3) was <0.5% (gas chromatography). The resin component had an amine equivalent weight (NH equivalent) of 177 g / mol.

[0193] Other aqueous dispersions containing polyamine component X2

[0194] 1200 g (1.2 mol or 2.4 OH equivalents) of an ethylene oxide-based polyalkylene polyether having an average molecular weight of 1200 g / mol and 1984.62 g (10.67 epoxy equivalents) of a bisphenol A diglycidyl ether-based epoxy resin having an average epoxy equivalent weight of 186.5 g / mol were mixed in a reaction vessel and the internal temperature was then raised to 120-130° C. with continuous stirring. Subsequently, 6.5 g of Anchor 1040 (BF3-monoethylamine catalyst) was added, the temperature was further raised to 160° C. and maintained at 160° C. for another 4 hours until an epoxy equivalent weight of 417 g / mol was reached. It was then cooled to 55° C. and 82.549 g of di-n-propylamine was added. Stirring was continued at 55° C. until an EEW of 482 g / mol was reached. It was then heated to 60° C. and a further 174.11 g of (demineralized) water was added.

[0195] 1605.22 g of isophorone diamine (corresponding to 9.4 mol or 37.77 NH equivalents) and 575.96 g of meta-xylylenediamine (corresponding to 4.2 mol or 16.91 NH equivalents) were mixed in a reactor and heated to an internal temperature of 60° C. Subsequently, 3447.78 g of the above reaction product were added over a period of 30 minutes with continuous mixing. This raised the internal temperature to about 75° C., and stirring was continued at this temperature for 90 minutes. Then, n-butyl glycidyl ether was added over a period of 20 minutes with stirring. This raised the internal temperature to about 80° C., and stirring was continued at this temperature for 60 minutes. Then, a further 1374 g of (demineralized) water were added, which cooled the product to 40° C.

[0196] The resin mixture present in the reaction mixture had an amine equivalent weight (NH equivalent weight) of 125 g / mol.

[0197] Other aqueous dispersions containing polyamine component X3

[0198] In a reactor, 897.41 g of (AD2) and 1868.00 g of demineralized water were heated to 95° C. with stirring. Subsequently, the mixture was cooled to 70° C., 163.44 g (0.437 mol) of a mixture of bisphenol A diglycidyl ether epoxy resin having an average epoxy equivalent of 186.5 g / mol, 39.46 g of a polyalkylene polyether epoxide based on polypropylene oxide having an average epoxy equivalent of 395 g / mol, and 81.96 g of ethoxypropanol were added; 81.47 g of methyl ethyl ketone and 81.72 g of isobutanol were metered in over 2 hours, and the mixture was kept at about 70° C. for a further hour.

[0199] The reaction product thus obtained was cooled to 45° C. The viscosity of the product at 25° C. was 150-500 mPas.

[0200] In the subsequent process step, the process solvents isobutanol and methyl ethyl ketone are removed from the product by distillation under reduced pressure. The residual isobutanol and methyl ethyl ketone content of the resulting aqueous dispersion is <0.5%.

[0201] The resin mixture present in the dispersion had an amine equivalent weight (NH equivalent) of 203 g / mol.

[0202] Other aqueous dispersions containing polyamine component X6

[0203] Dispersion X6 was prepared analogously to step (A) of dispersion (AD3), except that only meta-xylylenediamine was used instead of a mixture of isophoronediamine and meta-xylylenediamine. The proportion of meta-xylylenediamine was increased accordingly to ensure that the same molar amount of monomeric amine was used.

[0204] The resin mixture present in the dispersion had an amine equivalent weight (NH equivalent weight) of 100 g / mol.

[0205] Table A gives a further overview of aqueous dispersions comprising the prepared polyamine components. In addition, other dispersions which are commercially available are listed which are additionally used in aqueous coating compositions (see below).

[0206] Table A:

[0207]

[0208] Epoxy resins for coating compositions

[0209] The epoxy resins shown in Table A1 were used to prepare coating compositions as described further below.

[0210] Table A1:

[0211]

[0212] The data shown in Table 1A indicate that only epoxy resins DER917, EPOTEC Resin TW 5001, EPI-REZ5108, and Beckopox EP 2384w / 57WA are epoxy resins useful in accordance with the present invention.

[0213] Coating compositions of the present invention and comparative coating compositions

[0214] Various inventive and comparative coating compositions were prepared by the following general preparation method.

[0215] The base component (1) and the curing component (2) of the coating composition are prepared by combining the ingredients and mixing thoroughly. In the preparation of the base component (1), all or almost all of the individual ingredients of the base component are used in a bead mill for 30 minutes in each case, at a uniform rotation speed, using 2 cups containing 350 mL of beads (Silibeads Z, diameter 1.6-2.5 mm) for 2100 g of mill base to prepare an aqueous dispersion. The ingredients and their amounts are shown in Table BD below.

[0216] To prepare the coating composition itself, the binder components are each mixed with the curing components and optionally additional water. Within 1 hour of completion, the composition is used as described below, ie, it is applied to a substrate and subsequently cured.

[0217] Table B: Coating compositions having a binder component containing a polyamine component

[0218]

[0219]

[0220]

[0221] Added water V1 V2 V3 V4 V5 V6 V7 Weight Weight Weight Weight Weight Weight Weight water 15.5 12.0 16.0 17.0 6.5 13.0 0.0

[0222] index V1 V2 V3 V4 V5 V6 V7 Pigment to Binder Ratio (P / B) 1.6 1.4 1.0 1.4 1.4 1.1 0.8 DIN4 flow time, seconds 19 20 20 20 20 20 23

[0223] Table C: Coating compositions with epoxy resin-containing binder components

[0224]

[0225]

[0226] Added water E1 E2 E3 E4 E5 E6 E7 Weight Weight Weight Weight Weight Weight Weight water 0 0 11 5 0 2 0

[0227] index E1 E2 E3 E4 E5 E6 E7 Pigment to Binder Ratio (P / B) 1.1 1.1 1.4 1.4 1.1 1.2 1.0 DIN4 flow time, seconds 24 24 24 24 26 24 16

[0228] NB All binder components have good storage stability after preparation (ie after the dispersion process) (after 8 weeks of storage at 40° C., sedimentation and flow time in DIN cups, see above test method). The bead mill can be cleaned without difficulty by rinsing with water.

[0229] Table D: Other coating compositions having a binder component containing an epoxy resin

[0230]

[0231]

[0232] The binder components of NBE8, V9, E9, E10 and V13 and V14 have good storage stability after preparation (i.e. after the dispersion process) (after storage for 8 weeks at 40° C., sedimentation and change in flow time in the DIN cup were tested, see the above test method). The bead mill can be cleaned without difficulty by rinsing with water. The binder components of V8, V11 and E11 can likewise be prepared without difficulty using a bead mill and were found to be storage-stable. After preparation, a slightly tacky film remains in the mill and on the surface of the grinding beads, but is still removable. The binder components V10 and V12 cannot be prepared in the form of a homogeneous dispersion, but are irreversibly degraded during the grinding process, giving an inhomogeneous, tackified mixture. Further use thereof is not possible.

[0233]

[0234] Added water E8 V8 V9 E9 V10 V11 E10 V12 E11 V13 V14 Weight Weight Weight Weight Weight Weight Weight Weight Weight Weight Weight water 1 10 0 6 - 3 10 - 16 10 20

[0235] index E8 V8 V9 E9 V10 V11 E10 V12 E11 V13 V14 Pigment to binder ratio (P / B), ready to use 1.4 1.4 1.4 1.4 1.5 1.5 1.8 1.7 1.6 DIN4 flow time adjusted with water, seconds 23 22 19 22 - 22 23 - 22 25 20

[0236] Preparation of coating using coating composition

[0237] Using the coating compositions E1 to E11 and V1 to V14, multicoat paint systems were produced by the following general method.

[0238] First, the substrates were cleaned according to their material type, i.e., metal substrates were cleaned with Glasurit 360-4 Metal Cleaner, plastic parts were cleaned with Glasurit 541-30 Plastic Universal Cleaner, and old paint or factory primed new parts were cleaned with Glasurit 541-5 KH Silicone and Tar Remover.

[0239] Then sand according to the substrate: P80 for steel, abrasive pads for galvanized steel, P150 for aluminum, abrasive pads for plastic on its area, abrasive pads for old paint or new factory primed parts.

[0240] In the next step, the grinding debris is removed by a cleaner and dried. This is done using the same cleaner as previously used for each substrate. After rubbing dry, the application of the first surfacer can begin.

[0241] For this purpose, the binder and curing components and demineralized water were mixed as described above with a stirring rod and then applied with a spray gun (SATA BF100 RP 1.6 at 2.0 bar). Two complete spray passes were applied without intermediate flashing. After the second spray pass, the primer-surfacer was dried for 40 minutes at a target temperature of 60° C. The dry layer thickness was in each case 60-80 μm (Dualscope MP40, ED10 probe from Fischer) according to DIN EN ISO 2808, May 2007.

[0242] After the drying phase and the subsequent cooling phase, sanding was performed. For this purpose, a control black (09560 black from 3M) was applied to the coated surface. The surface was sanded flat using an eccentric sanding tool with a stroke of 5 mm (LEX3 from Festom) and P400 sandpaper (Standard from RODIM).

[0243] The surfaces were then cleaned with Glasurit 700-1 cleaner and a basecoat was applied.

[0244] For this purpose, Glasurit 90-1250 Deep Black was formulated. The components were mixed with a stirring rod and then applied with one of the approved spray guns (e.g. SATA 5000 HVLP 1.3, selected at 2.0 bar). Two rounds of masking spray and one round of effect spray were applied. Each round of spraying was followed by an intermediate or final flash of about 5 minutes until the surface had a matte appearance.

[0245] The layer thickness achieved was 10-15 μm (Dualscope MP40, ED10 probe from Fischer) according to DIN EN ISO 2808, May 2007.

[0246] A clear coat was applied as the final layer. For this purpose, Glasurit 923-630 HS Super Gloss Clearcoat VOC was formulated from:

[0247] The components were mixed with a stirring rod and then applied with one of the approved spray guns (e.g. SATA 5000 RP 1.3, 2.0 bar). For this purpose, two spraying passes were applied with a 3-minute flash in between. Subsequent drying was carried out at a target temperature of 60° C. for 30 minutes. A layer thickness of 50-60 μm was obtained (Dualscope MP40, ED10 probe, obtained from Fischer) according to DIN EN ISO 2808 of May 2007.

[0248] Performance and inspection of multi-layer paint systems

[0249] All prepared paint systems were checked for surface quality. The following measurements were performed:

[0250] Gloss and haze were measured with a haze-gloss meter from BYK-Gardner. Gloss was measured at an angle of 20°. Haze was measured according to DIN EN ISO 13803, February 2015 edition: Paints and varnishes-Determination of haze on paint films at 20°. Gloss was measured according to DIN EN ISO 2813; February 2015 edition: Paints and varnishes-Determination of gloss value at 20°, 60° and 85°.

[0251] DOI (distinctness of image) and leveling were measured on the painted panels with a Wave-Scan Dual instrument from BYK-Gardner. Long wave (LW) and short wave (SW) were determined.

[0252] The visual assessment of the paint condition is carried out under reproducible light conditions in front of a black background. The panels to be inspected and the reference samples or panels to be compared with each other should be viewed at different angles in order to detect all surface defects and features. The visual assessment of the paint condition can only be made relative to a comparison sample or standard. The result is a graded order. The transparency of the appearance of the masked painted surface is evaluated. Differences in the condition of the topcoat can be attributed to fine structures in the topcoat layer that are replicated from the substrate. The evaluation is therefore of the hiding properties of the topcoat over the basecoat. A "collapse" of the basecoat results in a degradation of the topcoat condition. Other surface defects such as craters, bubbles, pinholes, sagging, turbidity, etc. are recorded separately and are not covered by the umbrella term for paint condition.

[0253] In addition, the multilayer paint system is visually inspected for pores. For this purpose, the metal sheets are examined by means of a microscope. It is found here that surface defects that are visually visible (i.e. by the naked eye) at 10 or 20 times magnification in thin sections are pores in the first surfacer layer, which have been partially or completely filled with basecoat and / or clearcoat. In particular, under a stereomicroscope, the center of the fault is exposed by means of a scalpel through a number of thin sections. Sections with a thickness of about 10 micrometers are then cut continuously in the fault zone and applied to a microscope slide. For evaluation by light microscopy, a drop of immersion oil or glycerol is applied to the thin section and covered with a cover slip.

[0254] To quantify surface defects, the number of surface defects in the paint system was counted over an area as large as a DIN A4 paper.

[0255] Table E shows the corresponding results.

[0256] Table E:

[0257]

[0258] The results show that samples V8, V9 and V11 give very poor topcoat conditions compared to the actual painted coating compositions, and therefore correspondingly lead to poor optical properties (DOI, LW, SW) if they can be evaluated at all by measuring technology. In contrast, systems E8-E11 according to the invention all have good or at least still acceptable topcoat conditions. Systems V13 and V14 (polyamine dispersions as binder) have good topcoat conditions and correspondingly have essentially good optical properties. However, compared to the systems according to the invention, systems V13 and V14 show a very high number of micropores, which are visually apparent as significant surface defects.

Claims

1. A method for repairing a multi-layer paint system having defects, comprising applying a coating composition to the defective area, curing the coating composition to prepare a cured coating, and then sanding the cured coating, wherein the coating composition is a water-based two-component coating composition comprising: (1) a paint base component based on epoxy resin, and (2) a polyamine-based curing component, wherein the binder component (1) comprises at least one aqueous dispersion of at least one pigment (P) and / or filler (F) in at least one epoxy resin (E), And wherein the at least one epoxy resin (E) has: (i) a maximum sedimentation rate of not more than 17,500 μm / hour, measured in an optical cuvette centrifuge at an acceleration of 2,050 g, diluted to 30% solids with water; and a glass transition temperature of less than 0°C, measured by dynamic differential calorimetry at a heating rate of 10 K / minute, measured in run 2, or (ii) a maximum sedimentation rate of at least 12500 microns / hour and a glass transition temperature of at least 0°C.

2. The method of claim 1, wherein the at least one epoxy resin (E) has: (i) a maximum sedimentation rate of 2500 to 17500 microns per hour and a glass transition temperature of -30°C to less than 0°C, or (ii) a maximum sedimentation rate of 12,500 to 30,000 microns / hour and a glass transition temperature of 0-20°C.

3. The method of claim 1, wherein the at least one epoxy resin (E) has an epoxy equivalent weight of less than 500 g / mol.

4. The method of claim 1, wherein the at least one epoxy resin (E) has an epoxy equivalent weight of less than 250 g / mol.

5. The method of claim 2, wherein the at least one epoxy resin (E) has an epoxy equivalent weight of 100-500 g / mol.

6. The method of claim 2, wherein the at least one epoxy resin (E) has an epoxy equivalent weight of 150-250 g / mol.

7. The method of any one of claims 1 to 6, wherein the dispersion comprises all of the pigments and / or fillers used in the coating composition.

8. The method according to any one of claims 1 to 6, wherein the dispersion comprises no further epoxy resins besides the at least one epoxy resin (E).

9. The method of claim 7, wherein the dispersion comprises no further epoxy resins besides the at least one epoxy resin (E).

10. The method according to any one of claims 1 to 6, wherein the curing component (2) comprises a polyamine component having an NH equivalent weight of 50 to 500 g / mol.

11. The method of claim 10, wherein the polyamine component comprises at least one aqueous resin dispersion (AD), the aqueous resin dispersion (AD) comprising a resin component (R), the resin component (R) comprising at least one di- and / or polyfunctional monomeric primary and / or secondary amine (M) and a polyfunctional polymeric organic amine having primary and / or secondary amino groups, wherein the resin component (R) has an NH equivalent of 150-400 g / mol and a weight proportion of 5-15 wt% of the di- and / or polyfunctional monomeric organic amine (M).

12. The method according to any one of claims 1 to 6, wherein the molar ratio of the NH functional groups of the polyamine component in the curing component (2) to the epoxy groups of the epoxy resin in the binder component (1) is 0.7:1 to 0.95:

1.

13. The method of any one of claims 1 to 6, wherein curing is performed at a temperature of 20 to 80°C.

14. The method according to any one of claims 1 to 6, wherein after the sanding of the cured coating, the multicoat paint system is produced by applying a basecoat and a clearcoat and subsequently curing them jointly or separately.

15. A coating prepared by the method of any one of claims 1 to 14.

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