EP1554326A1

EP1554326A1 - Emulsifier-free microgel

Info

Publication number: EP1554326A1
Application number: EP03773532A
Authority: EP
Inventors: Horst Müller
Original assignee: Bollig and Kemper KG
Current assignee: Bollig and Kemper KG
Priority date: 2002-10-14
Filing date: 2003-10-13
Publication date: 2005-07-20
Also published as: DE10393994D2; US20060128859A1; US7521506B2; AU2003281950A1; WO2004035646A1

Abstract

The invention relates to an emulsifier-free microgel dispersion and to the use thereof.

Description

E m u l g a t o rf re i e s M i k ro g e l "

The present invention relates to a microgel and its use in a multi-layer coating, in particular in the serial coating of automobile bodies-in-white.

Multi-layer painting consisting of a total of four different layers (four-layer structure) is generally used for the series painting of automobile body shells, these four layers being applied one after the other in separate painting systems:

The first layer, which is located directly on the car sheet, is an electrophoretically applied layer (electrocoat layer, KTL layer), which is applied by electro-dip coating - mainly cathodic dip coating (KTL) - for corrosion protection and then baked.

The second layer, located on the electrocoat layer and about 30 to 40 μm thick, is a so-called filler layer, which on the one hand offers protection against mechanical attacks (stone chip protection function) and on the other hand ensures a sufficient level of topcoat, i.e. the rough surface of the body-in-white for the subsequent top coat smoothes and fills in small bumps. The lacquers used to produce this filler layer contain pigments as well as binders. The wettability of the pigments used has an influence on the top coat level of the entire multi-layer coating and also on the gloss of the filler layer, as required by some automobile manufacturers. The filler layer is largely produced by application with electrostatic high-speed rotary bells and subsequent baking at temperatures above 130 ° C.

The third layer on the filler layer is the basecoat layer, which gives the body the desired color through the use of appropriate pigments. The basecoat is applied by conventional spraying. The layer thickness of this conventional basecoat is between about 12 to 25 μm depending on the color. This layer is usually applied in two process steps, especially with metallic effect paints. In a first step, the application is carried out using electrostatic high-speed rotary bells, followed by a second application using pneumatic atomization. This layer is dried (when using an aqueous basecoat) with infrared radiators and / or by hot air convection. The fourth and uppermost layer on the basecoat is the clearcoat, which is usually applied in one application using high-speed electrostatic bells is applied. It gives the body the desired gloss and protects the basecoat from environmental influences (UV radiation, salt water, etc.). Then the basecoat and the clearcoat are baked together.

A water-borne basecoat or a basecoat layer made from it can be used in this multi-layer paint system in addition to the color-providing properties. On the one hand, the hardened state of the basecoat layer must lead to an optimal alignment of the aluminum flakes used as effect pigments. This property, known under the term “flip / flop effect”, is of crucial importance for any metallic paint finish. A particularly good “flip / flop effect” is achieved when the flake-like effect pigments are aligned as evenly as possible at a flat angle to the paint layer.

In addition, the basecoat must have a precisely defined adhesion to the paint layers below and above it. This means that the basecoat has a decisive influence on the stone chip resistance of the resulting multi-layer coating of series car bodies. In this context it should be noted that the stone chip resistance is a so-called "co-criterion", ie only those multi-layer coatings that have previously passed the VDA stone chip test may be used in production. This test is passed when the finished multi-layer coating with a precisely defined mechanical load, flaking which does not exceed a certain area and which can be attributed to a separation of the basecoat layer from the filler layer underneath it. Consequently, the adhesion of the basecoat layer must be adjusted in such a way that it is high enough so that the Clear coat does not detach from it, but is nevertheless so low that it does not entrain the filler layer in the event of stone chips, which would otherwise lead to considerable corrosion damage to the automobile body.

On the other hand, the basecoat must be easy to process. This means that if possible in a spray application such a thick layer can be achieved that sufficient paint coverage is ensured. If only 17 μm thickness of the basecoat layer is required for sufficient color coverage for the strongly covering black color, it is at least 45 μm for the less covering color white. Applying such a layer thickness with a spraying process is still a considerable problem since the rheological properties of the water-borne basecoat must be present accordingly. In the case of basecoats with metallic effect pigments, the problem described above, ie ensuring adequate stability with a customary layer thickness of approximately 18 μm, is particularly clear. A particularly critical color in this context is silver metallic.

The term "rheological properties" is understood to mean that the lacquer, on the one hand during the spraying process, that is at high shear rates, has such a low viscosity that it can be easily atomized, and on the other hand, when it hits the substrate, that is to say at low shear rates high viscosity has that it is sufficiently stable and shows no runner formation. The higher the layer thickness, the greater the problem of combining these contradictory properties. The formation of a pronounced metallic effect is also related to these properties. This basic problem is probably the reason why a large number of publications deal with specially coordinated binder systems or also with special additives for water-borne basecoats.

Special additives are described to improve the theological properties and to improve the metallic effect (EP-0 281 936). These are special layered silicates that contain considerable amounts of alkali or alkaline earth ions. Because of their water-attracting effect, these ions often lead to poor condensation resistance in the overall structure of an automobile coating.

It is therefore an endeavor of the paint manufacturers to avoid such additives as far as possible and to use those polymers as binders which inherently have the desired properties, so-called “tailor-made” polymers.

One of the most important representatives of this species are crosslinked polymer microparticles present in aqueous dispersion, or "microgels" for short.

The addition of microgels not only improves the rheological properties, but also has a significant impact on the stability of the paint to be applied, the alignment of the effect pigments and the adhesion of the basecoat to the filler layer underneath, and thus has a decisive influence on the stone chip resistance of the multi-layer coating , However, it should be noted that the addition of microgels does not have a positive effect on all of the properties mentioned above: Special microgels are known from EP 0 030 439 B1 and EP 0 242 235 A1. However, the aqueous microgel dispersions described there as also advantageous for metallic coatings are not completely crosslinked microgels but rather belong to the so-called “gore / shell” - or also referred to as “core / shell” - microgels. The term “core / shell structure” is understood to mean that the polymer particle is essentially composed of two different areas: the inner area (core) is surrounded by an outer area (shell), these areas having a different chemical composition and This also results in different physical properties. The core of this microgel is obtainable from a mixture which, in addition to monofunctional monomers, also contains difunctional monomers. Crosslinking is carried out using an emulsifier. This is then crosslinked microparticle in accordance with EP 0 030 439 B1 a layer of non-crosslinked acrylic polymer is coated and grafted in. According to EP 0 242 235 A1, the crosslinked microparticle is coated with a layer of polymerizable aromatic compounds.

EP 0 030 439 B1 also describes converting the microgels present in aqueous dispersion into a non-aqueous phase and using them for solvent-containing coating compositions.

Microgels are also known from EP 0 038 127 B1, EP 0 029 637 A1 and GB 2 159 161 A, which can be obtained by polymerizing suitable monomers in the presence of an emulsifier, for example N, N-bis (hydroxyethyl) taurine. The term “emulsifier” is to be understood as meaning those compounds which have both a hydrophilic and a hydrophobic residue. Emulsifiers bring about a stabilization of emulsions, ie of disperse systems of two immiscible or only partially miscible liquids or phases, of which one is finely divided into the other. A further definition of such compounds is given, for example, in "Römpps Chemie Lexikon" (Vol. 2, 8th edition, 1981, pp. 1126-1127). A general distinction is made between ionic, non-ionic and amphoteric emulsifiers. For color-imparting coating compositions, emulsifiers are used which have a group derived from sulfonic acid as the hydrophilic radical and a longer-chain fatty alkyl radical as the hydrophobic radical. A major disadvantage of the microgels produced using an emulsifier is that the emulsifier remains in the finished microgel, since the latter, for example because of the sulfur-containing groups (sulfonic acid groups) present in the emulsifier, can only be used with considerable disadvantages for a large number of applications , Such microgels have disadvantageous properties due to the emulsifier they contain, for example with regard to Ren use in water-thinnable basecoats in the automotive industry, especially with regard to water storage and condensation resistance.

Furthermore, from DE 36 06 513 C2 microgels are known which are first prepared in an organic solvent from a polyester component and a partially blocked isocyanate component. The organic solvent is then distilled off and the solvent is changed to a dispersion in water.

However, a disadvantage of the microgels obtainable in this way is that when they are used in coating compositions, no reproducible results are obtained with regard to solids concentration and level of properties, which precludes industrial use.

In addition, DE 41 22 266 A1 describes polymers which can be used for the production of basecoats and adhesives. The resulting polymer particles are film-forming and are not cross-linked to such an extent that they could guarantee the requirements for the aluminum orientation and stability required by the automotive industry.

Furthermore, from US 6 462 139 B1 film-forming compositions are known which are used for the production of clearcoats and basecoats. The polymer microparticles disclosed there are only subsequently reacted with a crosslinking agent which contains either blocked isocyanate groups or an aminoplast resin. With the microgels described here, however, it is necessary to carry out a dispersion step using a microfluidiser, since otherwise a stable dispersion in water cannot be achieved.

EP 0 502 934 also describes a microgel dispersion. This serves both to improve the rheological properties and to increase the gassing stability of aqueous metallic basecoats. These microgel dispersions are produced by a single-stage polycondensation of a polyester polyol with an aminoplast resin (melamine resin) in the aqueous phase.

However, the use of this microgel in basecoats in the painting of automobile bodies has the disadvantage that the adhesion between the basecoat layer and a clearcoat layer located thereon and made from a powder clearcoat or a powder clearcoat slurry does not meet the requirements prescribed by the automotive industry.

Furthermore, from DE 195 04 015 A1 microgels are known which are obtained by polymerizing an ethylenically monofunctional compound (polyacrylate) with at least one ethylenically di- or multifunctional compound in the presence of a polyester. The polyester acts as an emulsifier and stabilizer. The disadvantage of these microgels is that the rheological properties of these coatings no longer meet the increased requirements of the automotive industry. This is particularly evident in terms of the requirements for viscosity on the one hand and for stability on the other.

Using these microgels, it is not possible to provide an aqueous basecoat that has a maximum viscosity of 120 mPa-s at a shear rate of 1,000 s ^_1 and is so stable that the necessary layer thicknesses of 20 - 30 μm ( depending on the respective color, also lower or higher) can be achieved without running.

Furthermore, in WO 00/63265 and WO 00/63266 microgels are known which can be obtained from a multistage polymerization process, in a first step a polymerization of ethylenically monofunctional compounds with ethylenically di- or multifunctional compounds in the presence of a polyester polyol, polyurethane and / or polyacrylate is carried out. As the last step, the product obtained in this way is reacted with a crosslinking agent, so that a completely crosslinked microgel is obtained. This completely crosslinked microgel is then added to binder formulations which necessarily contain a crosslinkable binder. When the finished lacquer film is formed, for example under a baking condition, the binder is then crosslinked - the microgel added to the binder formulation cannot participate in this crosslinking because of the lack of functionalities. A problem with the use of these subsequently crosslinked microgels is that water-thinnable basecoats containing these microgels do not show sufficient adhesion on plastic substrates to be coated directly on a plastic surface, for example on automobile bumpers, without an intermediate or adhesive base layer.

The object of the present invention is to provide a water-dilutable microgel which can be used in water-dilutable basecoats, in particular for the automotive industry. The multi-layer coatings obtainable therefrom are intended to overcome the disadvantages of the prior art described above, in particular the coloring layer should have sufficient adhesion to plastic substrates and the overall property level of the finished multi-layer coating should meet the high requirements of the automobile manufacturers (in particular with regard to appearance and stone chip resistance) , In addition, this microgel is said to be particularly compatible with binder systems based on polyurethanes and / or polyacrylates, and to give particularly high-quality coatings.

This object is achieved according to the invention by an emulsifier-free microgel dispersion obtainable by intermolecular or intramolecular crosslinking in an aqueous medium of a prepolymer, the prepolymer

• at least two blocked NCO groups;

• at least three groups with at least one active hydrogen atom bound to a nitrogen atom;

• in the backbone of the prepolymer at least one segment originating from a triol, polyol, linear and / or branched polyester polyol; and

• has at least one group capable of forming anions and, in the case of intermolecular or intramolecular crosslinking, the nitrogen atoms carrying at least one active hydrogen atom react with the blocked NCO groups to form urea bonds and to release the blocking agent.

This object is also achieved by an emulsifier-free microgel dispersion, obtainable by intermolecular or intramolecular crosslinking in an aqueous medium of a prepolymer, the prepolymer

• at least three blocked NCO groups;

• at least two groups with at least one active hydrogen atom bound to a nitrogen atom; • in the backbone of the prepolymer at least one segment originating from a triol, polyol, linear and / or branched polyester polyol; and

The emulsifier-free microgel dispersions according to the invention are aqueous, give coating compositions which contain these emulsifier-free microgel dispersions an increased structural viscosity, so that adequate stability is ensured during application, the resulting coating compositions being both chemically and physically curable. In the context of the present invention, the property "aqueous" means that the dispersions according to the invention contain no or only minor amounts of organic solvents. Minor amounts are those amounts which do not destroy the aqueous nature of the dispersions according to the invention. The property "pseudoplastic" means that coating compositions containing these emulsifier-free microgel dispersions are smaller at higher shear stresses or higher speed gradients than at low values (cf. Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, page 546, "Shearth Viscosity"). This structural viscosity is independent of time. This time independence means that the course of the viscosity as a function of the shear rate is identical both with increasing shear rate and with decreasing shear rate. This pseudoplastic behavior takes into account the needs of the spray application on the one hand and the requirements with regard to storage and settling stability on the other:

In the agitated state, for example when pumping around a coating composition which contains the microgels according to the invention, in the ring line of the painting system and when spraying, the coating composition assumes a low-viscosity state which ensures good processability. Without shear stress, however, the viscosity increases and in this way ensures that the coating composition already on the substrate surface shows a reduced tendency to run off on vertical surfaces (“runner formation”). In the same way, the higher viscosity in the unmoved state, such as during storage, means that any solid constituents such as pigments that may be present are largely prevented or the solid constituents which are only weakly sedimented during the storage period are stirred up again.

In the context of the present invention, the term "physical hardening" means the hardening of a layer of a coating material by filming by release of solvent from the coating material, the linkage within the coating via loop formation of the polymer molecules, film-forming components or the binders (for the term cf. Römpp Lexikon Lacquers and printing inks, Georg Thieme Verlag, Stuttgart, New York, 1998, "Binders", pages 73 and 74), but not with the microgels according to the invention. Or the filming takes place via the coalescence of binder particles (cf. Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, "Härtung", pages 274 and 275). No crosslinking agents are usually necessary for this. Gegebenen- if physical hardening can be supported by heat or exposure to actinic radiation.

In contrast, the term “chemical hardening” means the hardening of a layer of a coating material by chemical reaction (see “hardening of plastics” in Römpps Chemie Lexikon, 8th ed., 1983, p. 1602 f.) chemical hardening achieved by atmospheric oxygen or by crosslinking agents.

The polyester polyol used for the present invention is a compound which is obtainable from the polycondensation of at least one of the diols or polyols described above with at least one polycarboxylic acid or its anhydride. Examples of suitable polycarboxylic acids are aromatic, aliphatic and cycloaliphatic polycarboxylic acids. Aromatic and / or aliphatic polycarboxylic acids are preferably used.

Examples of suitable aromatic polycarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic acid, isophthalic acid or terephthalic acid monosulfonate, of which isophthalic acid and trimellitic acid anhydride are advantageous and are therefore used with preference.

Examples of suitable acyclic, aliphatic or unsaturated polycarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, or dimer fatty acids or maleic acid, fumaric acid or itaconic acid, of which adipic acid, glutaric acid, azelaic acid, sebacic acid , Dimer fatty acids and maleic acid are advantageous and are therefore preferably used. Examples of suitable cycloaliphatic and cyclic 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 Methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid, tetrahydrophthalic acid or 4-methyltetrahydrophthalic acid. These dicarboxylic acids can be used both in their ice and in their trans form and as a mixture of both forms. Also suitable are the transesterifiable derivatives of the abovementioned polycarboxylic acids, such as, for example, their mono- or polyvalent esters with aliphatic alcohols with 1 to 4 carbon atoms or hydroxy alcohols with 1 to 4 carbon atoms. In addition, the anhydrides of the above-mentioned polycarboxylic acids can also be used if they exist. If appropriate, monocarboxylic acids can also be used together with the polycarboxylic acids, such as benzoic acid, tert-butylbenzoic acid, lauric acid, isononanoic acid, fatty acids of naturally occurring oils, acrylic acid, methacrylic acid, ethacrylic acid or crotonic acid. Isononanoic acid is preferably used as the monocarboxylic acid.

In addition to the diols, triols are usually used in minor amounts in order to introduce branches into the polyester polyols.

1, 6-Hexanediol and neopentyl glycol are particularly advantageous as diols and are therefore used with particular preference. Further examples of suitable polyols are polyester diols which are obtained by reacting a lactone with a diol. They are characterized by the presence of any hydroxyl groups and recurring polyester components of the formula - (- CO- (CHR) _m -CH ₂ -O -) -. The index m is preferably 4 to 6 and the substituent R = hydrogen, an alkyl, cycloalkyl or alkoxy radical. No substituent contains more than 12 carbon atoms. The total number of carbon atoms in the substituent does not exceed 12 per lactone ring. Examples include hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid and / or hydroxystearic acid. For the preparation of the polyester diols, the unsubstituted ε-caprolactone, in which m is 4 and all R substituents are hydrogen, is preferred. The reaction with lactone is started by low molecular weight polyols such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol or dimethylolcyclohexane. However, other reaction components, such as ethylenediamine, alkyldialkanolamines or urea, can also be reacted with caprolactone. Also suitable as higher molecular weight diols are polylactam diols which are prepared by reacting, for example, ε-caprolactone with low molecular weight diols.

Further examples of suitable polyols are polyether polyols, in particular with a number average molecular weight from 400 to 5,000, in particular from 400 to 3,000. Suitable polyether polyols are, for example, polyether diols of the general formula H - (- O- (CHR) ₀ -) pOH, where the substituent R = hydrogen or a lower, optionally substituted alkyl radical, the index o = 2 to 6, preferably 3 to 4 , and the index p = 2 to 100, preferably 5 to 50. Linear or branched polyether diols such as poly (oxyethylene) glycols, poly (oxypropylene) glycols and poly (oxybutylene) glycols are mentioned as particularly suitable examples. On the one hand, the polyether diols should not introduce excessive amounts of ether groups, because otherwise the polyurethanes formed to be used according to the invention swell in water. On the other hand, they can be used in amounts which ensure the nonionic stabilization of the polyurethanes. Further examples of suitable polyols are poly (meth) acrylate diols, polycarbonate diols or polyolefin polyols such as POLYTAIL ^® from the Mitsubishi Chemical Group.

The term “at least one group capable of forming anions” is understood to mean those groups and / or segments which can be converted into anions in an aqueous environment by neutralizing agents. By selecting the type and the amount of such groups, the acid number of the polymer and above The acid number of the resulting microgel can be adjusted.Examples of suitable functional groups which can be converted into anions are carboxylic acid, sulfonic acid or phosphonic acid groups, in particular carboxylic acid groups.

In particular, the functional groups which can be converted into anions originate from compounds, dihydroxypropionic acid, dihydroxysuccinic acid, dihydroxybenzoic acid, dihydroxycyclohexane monocarboxylic acid and 2,2-dialkylolalkanoic acids of the formula

3 R OH

2 I R C COOH

R- - OH in which R ^{2 represents} a hydrogen atom or an alkyl group with up to 20 carbon atoms, R ³ and R ⁴ each independently represent linear or branched alkylene groups with 1 to 6 carbon atoms, preferably -CH2-. Examples of such compounds are 2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid and 2,2-dimethylolpentanoic acid. The preferred dihydroxyalkanoic acids are 2,2-dimethylolpropionic acid and 9,10-dihydroxystearic acid.

Examples of suitable neutralizing agents for functional groups which can be converted into anions are ammonia or amines, such as e.g. Trimethylamine, triethylamine, tributylamine, dimethylaniline, diethylaniline, triphenylamine, dimethylethanolamine, diethylethanolamine, methyldiethanolamine, 2-aminomethylpropanol, dimethylisopropylamine, dimethylisopropanolamine or triethanolamine. Dimethylethanolamine and / or triethylamine is preferably used as the neutralizing agent.

The term "neutralize" means that - based on the neutralizing agent used - a theoretically calculated degree of neutralization of at least 50% is set.

The theoretical degree of neutralization NG can be calculated using the following formula: , , _,. ",, M neutralizing agent * 5,610,000

NG (in%) ~

(SZ of neutral solid resin * M of neutral solid resin g) * MGW of neutralizing medium)

The term “polyisocyanate” is understood here and below to mean a compound which has at least two NCO groups. Consequently, this definition also includes diisocyanates.

The term “active hydrogen atom” is understood here and below to mean those hydrogen atoms which, under the reaction conditions customary in polyurethane chemistry, react with uncapped NCO groups to form urethane or urea bonds. In the case of at least one bonded to a nitrogen atom, active hydrogen atom is consequently a hydrogen atom originating from an NH group and / or an NH ₂ group.

If such an active hydrogen atom is not bound to a nitrogen atom, it preferably comes from an OH group.

The capped NCO groups which are mandatory for at least one of the starting compounds can be obtained by reacting corresponding free NCO groups with the customary capping or blocking agents known in polyurethane chemistry. In the case of the crosslinking according to the invention, it is found that the capping agent is released under reaction conditions. The formation of cross-linked particles can also be clearly observed.

Furthermore, urea bonds in the reaction product can be detected by IR spectroscopy; selective detection is possible in particular by means of nuclear magnetic resonance spectroscopic methods.

With regard to a detailed production of polyurethanes, their starting products and the techniques and processes for their modification, such as chain extension, crosslinking, reference is made to the literature by D. Dieterich “Aqueous Emulsions, Dispersions and Solutions of Polyurethanes; Synthesis and Properties "in Progress in Organic Coatings, 9 (1981), pp. 281 to 340;"Ullmann's Encyclopedia of Industrial Chemistry ", 5th edition, volume 21, pp. 665 to 716 and MJ Husbands et al. "A Manual of Resins for Surface Coatings", (1987) SITA Technology, London, Volume 3, pp. 1 to 59. The particular advantage of the emulsifier-free microgels according to the invention according to the previously described embodiments is that their addition to water-dilutable coating compositions brings about a clear and positive improvement in special properties.

In principle, it can be stated that the rheological properties of the water-dilutable coating compositions obtainable using this emulsifier-free microgel dispersion are improved over those of the prior art. For example, a water-thinnable basecoat which can be used in the automotive industry shows a viscosity of at most 100 mPa-s at a shear rate of 1,000 s ^{"" 1} even when 20% of the emulsifier-free microgel dispersion according to the invention is added, based on the solids content of the coating composition are obtained, the dry film thickness of the hardened basecoat layer being 22 μ, without any runners being observed.

The emulsifier-free microgel according to the invention is particularly suitable for the production and formulation of water-thinnable basecoats, in particular for those which are used in the automotive industry.

In addition, the emulsifier-free microgel dispersion according to the invention gives the coloring coating composition sufficient adhesion to plastic substrates. This property is particularly noteworthy, since this paint can be used in its unchanged formulation for metallic, pretreated substrates (automobile bodies) as well as for add-on parts for automobiles made of plastic (e.g. bumpers). This avoids color deviations. So far, it has often been necessary for the area of industrial applications, starting from water-thinnable basecoats for the serial painting of automobile body shells, to increase their adhesion to plastic substrates by adding so-called "adhesion promoters" or even by adding additional adhesive layers.

The excellent adhesion of the basecoats containing the microgel according to the invention can be seen from the "steam jet test" established in the automotive industry as a test for adequate adhesion.

Furthermore, the addition of the emulsifier-free microgel dispersion according to the invention to the coloring coating composition does not adversely affect the overall level of properties of the finished multilayer coating. So it shows finished multi-layer coating excellent properties with regard to mechanical (stone chip resistance) and optical criteria (ie orientation of the effect pigments).

Furthermore, the microgel dispersions according to the invention have excellent utility together with binder systems based on polyurethanes, polyacrylates or mixtures of polyurethanes and polyacrylates. This good usability is demonstrated in particular by the good adhesion properties of the resulting paint film on plastic substrates. Coating composition from a combination of binder system based on polyurethanes and / or polyacrylates and the emulsifier-free microgel dispersions according to the invention result in very high-quality coatings.

According to a particular embodiment of the present invention, more than 70% of the groups are reacted with at least one active hydrogen atom bonded to a nitrogen atom with the formation of polyurea bonds. Common to all of the previously described embodiments according to the invention is that the microgels present in dispersion are largely crosslinked.

The degree of crosslinking of the microgels can be recognized from the content of the insoluble components. The insoluble fractions are determined by means of the so-called "THF method". For this purpose, about 1 g of the microgel dispersion is weighed into a centrifuge tube, 10 ml of tetrahydrofuran are added and the mixture is homogenized in an ultrasound bath for about 1 minute. Then a centrifuge with a fixed angle is used -Rotor centrifuged at 13,500 rpm for 15 minutes, then the supernatant is carefully decanted off and the tube is dried in a laboratory oven for 6 hours at 105 ° C. After the tube has cooled, the residue is weighed out, and the insoluble fractions are calculated using the following formula :

% insoluble parts = =. _{Λ OI C} rcüpkstand 10000 _™ _-

Eιnwaag% Festkorpe _. ehaltder ιkrogel _3persιon

The term "largely crosslinked" is understood to mean those microgels which, based on the crosslinked part, have a proportion of uncrosslinked polymers of not more than 30% by weight.

With regard to the core / shell microgel according to the invention, this means that the crosslinked core is referred to as "largely crosslinked" if it contains no more than 30% by weight of uncrosslinked constituents. According to a preferred embodiment of the present invention, the group having at least one active hydrogen atom bonded to a nitrogen atom is an NH ₂ group.

Diamines and polyamines are to be mentioned as compounds having at least one NH ₂ group, in particular those having 1 to 40 carbon atoms, preferably about 2 to 15 carbon atoms. They can carry substituents that do not have hydrogen atoms that are reactive with isocyanate groups.

As diamines are hydrazine, ethylenediamine, propylenediamine, 1,4-butylenediamine, piperazine, 1,4-cyclohexyldimethylamine, hexamethylenediamine-1,6, trimethylhexamethylenediamine, methanediamine, isophoronediamine, 4,4'-diaminodicyclohexylmethane Aminoethylenethanolamin. Preferred diamines are hydrazine, alkyl- or cycloalkyldiamines such as propylenediamine and 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane. Hydrazine and adipic acid bishydrazide are particularly preferred.

Polyamines are taken to mean those compounds which have two or more primary and / or secondary amino groups. Examples of suitable polyamines are essentially alkylene polyamines. Examples are polyamines with a linear or branched aliphatic, cycloaliphatic or aromatic structure and at least two primary amino groups. Examples of polyamines are: • Alkylene polyamines with 1 to 40 carbon atoms, preferably with about 2 to 15 carbon atoms, with a linear or branched aliphatic, cycloaliphatic or aromatic structure and at least two primary amino groups, which may have substituents that do not have hydrogen atoms reactive with isocyanate groups.

According to a likewise preferred embodiment of the present invention, the polymer has • a number average molecular weight of more than 2,000;

• an acid number between 10 and 30 mg KOH / g;

• At least one segment derived from a diisocyanate as the hard segment.

According to the current state of knowledge, the number average molecular weight has a considerable influence on the rheology of the coating composition containing the emulsifier-free microgel dispersion according to the invention.

In general, a higher number average molecular weight causes an increase in the crosslinking points within the microgel (ie the mesh size of the polymer is increased). It is important here, however, that even with a high number-average molecular weight, sufficient stability of the dispersion is ensured with a degree of neutralization sufficient for stabilization in water.

According to a preferred embodiment of the present invention, the triol has 3 to 24 carbon atoms.

The triols to be mentioned are: glycerol, 1, 2,4-, 1, 3,5-trihydroxycyclohexane, trimethylolethane, 1, 2,4 butanetriol, 1, 2,6-hexanetriol and trimethylolpropane. Trimethylolpropane is preferred.

According to a likewise preferred embodiment of the present invention, the polyol has 3 to 12 carbon atoms.

Pentaerythritol, di-pentaerythritol and hydroxylated epoxidized linseed or soybean oils are to be mentioned as polyols. Di-trimethylolpropane is preferred.

In particular, the use of triplets or polyols ensures a higher functionality of the prepolymer, so that increased crosslinking is achieved, which is evident in the improved rheological properties of the coating compositions containing these microgel dispersions.

According to a further, likewise preferred embodiment of the present invention, the linear and / or branched polyester polyol is obtainable from the polycondensation of a polycarboxylic acid with at least one diol or polyol.

Examples of diols for this 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-pentanediol, 1, 2-, 1,3-, 1, 4-, 1,5- or 1,6-hexanediol, hydroxypivalic acid neopentyl ester, neopentyl glycol, diethylene glycol, 1, 2-, 1, 3- or 1,4-cyclohexanediol, 1,2-, 1,3- or 1,4-cyclohexanedimethanol, trimethylpentanediol, ethylbutylpropanediol, the positionally isomeric diethyloctanediols, 2-butyl-2-ethylpropanediol-1, 3, 2-butyl- 2-methylpropanediol-1,3,2-phenyl-2-methylpropanediol-1,3,2-propyl-2-ethylpropanediol-1,3,2-di-tert-butylpropanediol-1,3,2-butyl -2-propylpropanediol-1,3,1-dihydroxymethyl-bicyclo [2.2.1] heptane, 2,2-diethylpropanediol-1,3,2,2-dipropylpropanediol-1,3,2-cyclohexyl -2-methylpropanediol-1, 3, 2,5-dimethyl-hexanediol-2,5, 2,5-diethylhexanediol-2,5, 2-ethyl-5-methylhexanediol-2,5, 2,4-dimethylpentanediol -2,4, 2,3-dimethylbutanediol-2,3,1,4- (2'-hydroxypropyl) benzene, 1,3- (2'-hydroxypropyl) benzene, trimethylolpopane monoallyl ether or dimer diol (Unichema). The compounds described above can be selected as the diol or polycarboxylic acid.

According to a further, likewise preferred embodiment of the present invention, the linear or branched polyester polyol has a number average molecular weight between 300 and 4,000 and a hydroxyl number between 28 and 580.

By selecting a suitable low molecular weight polyol and a long-chain, linear and / or branched polyester polyol, a high crosslinking density is achieved, the distance between the respective crosslinking centers being sufficiently high that the rheological properties are positively influenced.

However, it is also possible to use a polyether polyol instead of a polyester polyol.

The blocked NCO groups, identical or different, originate from the reaction with a compound, which in turn results from the reaction of a polyisocyanate with a suitable capping agent. The term "blocking agent" is synonymous with the term "capping agent".

All compounds which are used in the production of water-dilutable basecoats are suitable as polyisocyanates. Examples of such polyisocyanates are: • aliphatic diisocyanates such as 1,1-methylenebis (4-isocyanatocyclohexane) (4,4'-dicyclohexylmethane diisocyanate, Desmodur W), hexamethylene diisocyanate (HMDI, 1,6-diisocyanatohexane, Desmodur H), isophorone diisocyanate (IPDI, 3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane), 1,4-cyclohexyl diisocyanate (CHDI, trans, -trans-1,4-diisocyanatocyclohexane); Aromatic triisocyanates such as tris (4-isocyanatophenyl) methane (Desmodur R), 1,3,5-tris (3-isocyanato-4-methylphenyl) -2,4,6-trioxohexahydro-1,3,5-triazine (Desmodur IL); Adducts from aromatic diisocyanates such as the adduct of 2,4-tolylene diisocyanate (TDI, 2,4-diisocyanatotoluene) and trimethylolpropane (Desmodur L); and / or • aliphatic triisocyanates such as N-isocyanatohexylaminocarbonyl-N, N'-bis (isocyanatohexyl) urea (Desmodur N), 2,4,6-trioxo-1,3,5-tris (6-isocyanatohexyl) hexahydro -1,3,5-triazine (Desmodur N3300), 2,4,6-trioxo-1,3,5-tris (5-isocyanato-1,3,3-trimethylcyclohexylmethyl) hexahydro-1,3,5-triazine (Desmodur Z4370). Particularly good results are obtained from the reaction of a diisocyanate such as 1,1-methylenebis (4-isocyanatocyclohexane) (4,4'-dicyclohexylmethane diisocyanate, Desmodur W), hexamethylene diisocyanate (HMDI, 1,6-diisocyanatohexane, Desmodur H), isophorone diisocyanate (IPDI , 3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane), 1, 4-cyclohexyl diisocyanate (CHDI, trans, -trans-1, 4-diisocyanatocyclohexane) with a capping agent, especially with methyl ethyl ketoxime. The use of TMXDI (m-tetramethylxylylenediisocyanate), which introduces the blocked NCO groups after reaction with a blocking agent, is very particularly preferred.

The term "capping agent" is understood to mean those compounds which react with the NCO groups of a polyisocyanate in such a way that the polyisocyanate capped in this way is resistant to hydroxyl groups at room temperature. At elevated temperatures, generally in the range of about 90 up to 300 ° C, the capped polyisocyanate reacts with elimination of the capping agent.

Any suitable aliphatic, cycloaliphatic or aromatic alkyl monoalcohols can be used for the capping (or also blocking) of the polyisocyanates. Examples include aliphatic alcohols such as methyl, ethyl, chloroethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl, 3,3,5-trimethylhexyl, decyl and lauryl alcohol ; aromatic alkyl alcohols, such as phenylcarbinol and methylphenylcarbinol. Small proportions of higher molecular weight and relatively poorly volatile monoalcohols can optionally also be used, these alcohols acting as plasticizers in the coatings after they have been split off. Other suitable capping agents are oximes, such as methyl ethyl ketone oxime, acetone oxime and cyclohexanone oxime, as well as caprolactams, phenols and hydroxy formic acid esters. Preferred capping agents are malonic esters, acetoacetic esters and β-diketones. The capped polyisocyanates are produced by reacting the capping agent with the organic polyisocyanate in sufficient quantity so that there are no longer any free isocyanate groups. Examples of suitable blocking agents are a) phenols such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, tert-butylphenol, hydroxybenzoic acid, esters of this acid or 2,5-di-tert-butyl-4-hydroxytoluene; b) lactams such as ,, - caprolactam, ,, - valerolactam, ,, - butyrolactam or ß-propiolactam; c) active methylenic compounds, such as diethyl malonate, dimethyl malonate, ethyl or methyl acetoacetate or acetylacetone; d) alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether colmonomethyl ether, methoxymethanol, glycolic acid, glycolic acid ester, lactic acid, lactic acid ester, methylolurea, methylolmelamine, diacetone alcohol, ethylene chlorohydrin, ethylene bromohydrin, 1, 3-dichloro-2-propanol, 1, 4-cyclohexyldimethanol, acetocyanhydrin or furanmethanol e) mercaptans such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol or ethylthiophenol; f) acid amides such as acetoanilide, acetoanisidinamide, acrylamide, methacrylamide, acetic acid amide, stearic acid amide or benzamide; g) imides such as succinimide, phthalimide or maleimide; h) amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, diisopropylamine or butylphenylamine; i) imidazoles such as imidazole or 2-ethylimidazole; j) ureas such as urea, thiourea, ethylene urea, ethylene thiourea or 1,3-diphenylurea; k) carbamates such as phenyl N-phenylcarbamate or 2-oxazolidone; I) imines such as ethyleneimine; m) oximes such as acetone oxime, formal doxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diisobutyl ketoxime, diacetyl monoxime, benzophenone oxime or chlorohexanone oxime; n) salts of sulfurous acid such as sodium bisulfite or potassium bisulfite; o) hydroxamic acid esters such as benzyl methacrylohydroxamate (BMH) or allyl methacrylohydroxamate; or p) substituted pyrazoles, in particular dimethylpyrazole or triazoles; and q) mixtures of these blocking agents, in particular dimethylpyrazole and triazoles, malonic esters and acetoacetic acid esters or dimethylpyrazole and succinimide.

For the purposes of the present invention, methyl ethyl ketoxime is particularly preferred as the capping agent.

In order to counter the risk of gelling, the previously described polyisocyanates can be partially capped. This means the reaction of the polyisocyanate with a capping agent in deficit. However, this does not partially mask the entire polyisocyanate. The mixture of partially capped polyisocyanate and remaining, uncapped polyisocyanate obtainable in this way is then subsequently reacted with the other components to give an emulsifier-free microgel dispersion.

In addition to the previously described embodiments, the microgel in its backbone can also have other structural units or segments that originate from the usual starting components used in paint chemistry. For example, the polymer A and / or B can contain polyurethane segments which originate from the previously described, uncapped polyisocyanates and compounds containing hydroxyl groups (e.g. diols, polyester polyols, polether).

Also preferred is an embodiment of the present invention in which the group capable of forming anions originates from dimethylolpropionic acid, 9,10-dihydroxystearic acid and / or from a polyester polyol with at least one group capable of forming anions.

These specially selected compounds give the dispersion significantly improved stability.

The group capable of forming anions from a polyester polyol can have, on average, at least one free carboxyl group per molecule, which comes in particular from trimellitic acid, trimellitic anhydride, dimethylolpropionic acid or dihydroxystearic acid.

The functionality which is decisive for the stability of the dispersion is thus introduced via an additional connection, so that the risk of gelling during the preparation of the prepolymer is prevented and at the same time an increased functionality of the prepolymer building blocks is achieved.

The group capable of forming anions can likewise originate from a diamine or polyamine.

In this way it is achieved that the backbone of the and / or the polymers can contain further functional groups which enable stronger crosslinking without the stability of the dispersion being adversely affected. Because the increasing functionality of the prepolymer increases the risk of premature gelling. The introduction of the group capable of forming anions by means of the chain extender enables the introduction of those necessary for the stability of the dispersion. leaving group at a time when crosslinking of the prepolymer is not expected.

However, it is also possible for the compound having at least one group capable of forming anions to have further functional groups, such as is e.g. is the case with compounds containing amino groups. In this connection, examples include α, δ-diaminovaleric acid, 3,4-diaminobenzoic acid, 2,4-diamino-toluenesulfonic acid (5) and 4,4'-diamino-diphenyl ether sulfonic acid. These compounds bring about the incorporation of the group capable of forming anions and at the same time have an active hydrogen atom bonded to a nitrogen atom which reacts with the blocked NCO group of polymer A to release the capping agent and form a urea bond.

If the risk of gelling during the production of the starting polymers is to be reduced, emulsifier-free microgel dispersions are preferred in which the group capable of forming anions originates exclusively from the diamine or polyamine.

Of course, other influences known to the person skilled in the art (quantity and type of

Solvent, the nature of the building blocks of the backbone and their influence on the molecular weight distribution) have a not inconsiderable influence on the risk of gelling.

The group capable of forming anions can also originate exclusively from the diamine or polyamine, and it is advantageous that this group capable of forming anions is a sulfonic acid group. Diaminoalkylsulfonic acid compounds may be mentioned as preferred compounds in this connection.

It is particularly preferred if at most one group capable of forming anions is present per 8,000 number-average molecular weight units. As a result, the theological properties of the coating composition containing the emulsifier-free microgel dispersion according to the invention can be further improved.

In addition, a further embodiment of the present invention is preferred, in which the number-average molecular weight of the prepolymer is at most 10,000, preferably between 3,000 and 7,000.

This achieves an optimal range for a sufficiently high degree of crosslinking with a sufficiently large mesh size. According to the state of knowledge to date, the number average molecular weight has a considerable influence on the rheology of the coating composition containing the emulsifier-free microgel dispersion according to the invention. In general, a higher number average molecular weight causes an increase in the crosslinking points within the microgel (ie the mesh size of the polymer is increased).

It is important here, however, that even with a high number-average molecular weight, sufficient stability of the dispersion is ensured with a degree of neutralization sufficient for stabilization in water. Microgels can be obtained even with a 100% degree of neutralization.

According to a further embodiment of the present invention, the crosslinking is carried out in the presence of an additional polymer with an OH number between 30 and 400 and an acid number between 1 and 150, the polymer being selected from the group of polyacrylates, polyesters and polyurethanes.

In this embodiment according to the invention, the hydroxyl-containing polymer can participate in the crosslinking to the microgel.

If this polymer is water-dilutable, this polymer is dispersed in water after the solution polymerization under the measures known per se. Otherwise, a premix is formed from the non-water-dilutable polymer together with the polymer A not yet dispersed in water, which is then subjected to dispersion in water.

This polymer can be added in an amount between 5 and 30% by weight, based on the solids, of the entire coating composition. The corresponding acid number of the additional polymer is achieved by incorporating a group capable of forming anions in a manner known per se.

This embodiment leads to a further improvement in the stability and alignment of the effect pigments. In addition, the adhesion of the coating composition containing the emulsifier-free microgel dispersion according to the invention is increased.

Suitable polyacrylates are obtainable by solution polymerization of monomers containing hydroxyl groups and alkyl (meth) acrylates, and optionally (meth) acrylic acid, styrene and / or ethylenically unsaturated monomers.

Suitable monomers containing hydroxyl groups are described in detail below. All monomers with at least one polymerizable double bond, as are described in detail below, can be used as ethylenically unsaturated monomers.

Solvents not containing hydroxyl groups are used as solvents for this solvent polymerization, particularly preferably ketones, such as e.g. Methyl ethyl ketone, methyl isobutyl ketone or methyl amyl ketone.

Suitable hydroxyl-containing polyesters are those as listed under the following description of the polyester polyols.

Suitable polyurethanes are obtainable from the reaction of at least one diol, polyol, polyether and / or a polyester polyol with at least one polyisocyanate for the purposes of the present invention.

In a further, likewise preferred embodiment of the present invention, the crosslinking is carried out together with an emulsion polymerization, using

At least one monomer compound which contains at least one free-radically polymerizable double bond, and

• at least one hydroxyl group-containing monomer compound which contains at least one free-radically polymerizable double bond.

The microgels produced from them, which are in dispersion, show a wide-ranging crosslinking density. A particular advantage of such an emulsifier-free microgel dispersion lies in a further improvement in the orientation of the effect pigments, increased adhesion and improved stability.

As a result, the rheological properties of the coating composition containing the emulsifier-free microgel dispersion according to the invention can be further improved.

In this embodiment, the hydroxyl group-containing monomer compound or the emulsion polymer linked via this hydroxyl group-containing monomer compound can participate in the crosslinking to form the microgel. The microgels produced in this way show no Gore / Shell structure.

Monomers with at least one free-radically polymerizable double bond which have no hydroxyl group are, for example • vinylaromatic compounds, such as vinyltoluenes, α-methylstyrene, p-, m- or p-methylstyrene, 2,5-dimethylstyrene, p-methoxystyrene, p-ter.-butylstyrene, p-dimethylaminostyrene, p-acetamidostyrene and m Vinylphenol, particularly preferably styrene;

• esters of acrylic or methacrylic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, isopropyl (meth) acrylate , Pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, -ethyl-hexyl (meth) acrylate, furfuryl (meth) acrylate, octyl (meth) acrylate, 3,5,5-trimethylhexyl- (meth ) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, stearyl (meth) acrylate and ethyl triglycol (meth) acrylate; Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate;

• acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid;

• aminoethyl acrylate, aminoethyl methacrylate, allylamine, N-methyliminoethyl acrylate or tert-butylaminoethyl methacrylate; • N, N-di (methoxymethyl) aminoethyl acrylate or methacrylate or N, N-di (butoxymethyl) aminopropyl acrylate or methacrylate;

• (Meth) acrylic acid amides such as (meth) acrylic acid amide, N-methyl, N-methylol, N, N-dimethylol, N-methoxymethyl, N, N-di (methoxymethyl), - N-ethoxymethyl and / or N, N-di (ethoxyethyl) - (meth) acrylamide; • Acryloyloxy or methacryloyloxyethyl, propyl or butyl carbamate or - allophanate; further examples of suitable monomers containing carbamate groups are described in US Pat. Nos. 3,479,328, 3,674,838, 4,126,747, 4,279,833 or 4,340,497;

• Monomers containing epoxy groups, such as the glycidyl ester of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid or allyl glycidyl ether.

The following are to be mentioned as monomer compounds containing hydroxyl groups with at least one free-radically polymerizable double bond: • Hydroxyalkyl esters of acrylic acid, methacrylic acid or another α, β-olefinically unsaturated carboxylic acid which are derived from an alkylene glycol which is esterified with the acid, or which are reacted by reacting the α , ß-olefinically unsaturated carboxylic acid with an alkylene oxide such as ethylene oxide or propylene oxide are available, in particular hydroxyalkyl esters of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid, in which the hydroxyalkyl group contains up to 20 carbon atoms, such as 2-hydroxyethyl -, 2-hydroxypropyl, 3-hydroxypropyl, 3-hydroxybutyl, 4-hydroxybutyl acrylate, - (meth) acrylate, -ethacrylate, -crotonate, -maleinate, -fumarate or -itaconate; or hydroxycycloalkyl esters such as 1,4-bis (hydroxymethyl) cyclohexane, octahydro-4,7-methano-1 H-indene-di- methanol or methyl propane diol monoacrylate, monoethacrylate, monoethacrylate, monocrotonate, monomaleinate, monofumarate or monoitaconate;

• reaction products from cyclic esters, such as. B. ε-caprolactone, and the previously described hydroxyalkyl or cycloalkyl esters (available for example under the name Tone ^® M 100 from DOW Chemicals);

Unsaturated polyols such as trimethylolpropane mono- or diallyl ether or pentaerythritol mono-, di- or triallyl ether;

• Reaction products from acrylic acid and / or methacrylic acid with the glycidyl ester of a monocarboxylic acid with 5 to 18 carbon atoms per molecule branched in the α-position, in particular one Versatic ^® acid, or instead of the reaction product, an equivalent amount of acrylic and / or methacrylic acid which is then reacted during or after the polymerization reaction with the glycidyl ester of a monocarboxylic acid having 5 to 18 carbon atoms per molecule, in particular a Versatic ^® acid, branched in the α-position.

In a further preferred embodiment of the present invention, the emulsifier-free microgel dispersion is characterized in that the reaction mixture originating from the crosslinking is subsequently subjected to an emulsion polymerization of at least one monomer compound which contains at least one free-radically polymerizable double bond.

This monomer compound with at least one free-radically polymerizable double bond contains hydroxyl groups particularly preferably.

Such an emulsifier-free microgel, which is present in dispersion, is present in a core / shell structure. The inner area is completely networked according to the definition given above. However, the outer area of this core / shell microgel is not networked. When using a monomer compound with at least one free-radically polymerizable double bond, the outer shell is crosslinked only under baking conditions for the production of corresponding multi-layer coatings.

Partial crosslinking in the finished lacquer via the outer shell is only guaranteed if a monomer compound containing hydroxyl groups with at least one radical-polymerizable double bond is used.

According to this embodiment, the polymerized monomer mixture does not participate in the crosslinking to the microgel.

In addition, a coating composition containing this emulsifier-free microgel dispersion shows such excellent adhesion that it can also be used in can be used as critical multi-layer coatings, especially in connection with powder clearcoats, in automotive OEM painting.

In the core / shell polymers or microgels described above, according to a preferred embodiment, only those monomers with at least one free-radically polymerizable double bond that do not contain any hydroxyl groups are used.

The use of a monomer compound without hydroxyl groups surprisingly reinforces this positive adhesion property.

Such an emulsifier-free microgel, which is present in dispersion, is present in a core / shell structure. The inner area is completely networked according to the definition given above. The outer area of this core / shell microgel is also not networked. In contrast to the core / shell polymer described above, the outer shell cannot be crosslinked under baking conditions for the production of appropriate multi-layer coatings.

According to this embodiment it is ensured that the emulsion polymer cannot participate in the crosslinking during film formation. This ensures excellent adhesion to plastic substrates, even in conjunction with powder clearcoats.

Higher functional monomers of the type described above are generally used in appropriate amounts. In the context of the present invention, corresponding amounts of higher-functional monomers are to be understood as those amounts which lead to crosslinking, but not to gelation of the microgel dispersion.

The orientation of the effect pigments is significantly improved when using emulsifier-free microgel dispersions according to this embodiment in aqueous metallic basecoats.

The object is also achieved according to the invention by an emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A dispersed in an aqueous medium and a polymer B, where

Polymer A has at least two blocked NCO groups;

• the polymer B has at least three groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer A and / or the polymer B • in the backbone at least one segment originating from a diol, polyol, polyether and / or a polyester polyol; and

• have at least one group capable of forming anions and during the crosslinking the nitrogen atoms carrying at least one active hydrogen atom react with the blocked NCO groups to form urea bonds and to release the blocking agent.

This object is also achieved by an emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A and a polymer B dispersed in an aqueous medium, where

Polymer A has at least three blocked NCO groups;

• the polymer B has at least two groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer A and / or the polymer B • in the backbone at least one segment originating from a diol, polyol, polyether and / or a polyester polyol ; and

This object is likewise achieved by an emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A dispersed in an aqueous medium with a polyamine, where • the polymer A has at least two blocked NCO groups;

• the polyamine has at least three groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer

• in the backbone at least one segment originating from a diol, polyol, polyether and / or a polyester polyol; and

• Has at least one group capable of forming anions, and during the crosslinking the nitrogen atoms carrying at least one active hydrogen atom react with the blocked NCO groups to form urea bonds and to release the blocking agent.

This object is also achieved by an emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A dispersed in an aqueous medium with a polyamine, where • the polymer A has at least three blocked NCO groups; • the polyamine has at least two groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer

• has at least one group capable of forming anions and during the crosslinking the nitrogen atoms carrying at least one active hydrogen atom react with the blocked NCO groups to form urea bonds and to release the blocking agent.

The number average molecular weight of polymer A and / or polymer B in one of the aforementioned embodiments of the invention is at most 10,000, preferably between 2,000 and 8,000.

According to a preferred embodiment of the present invention, polymer A, which additionally contains two uncapped NCO groups, is chain-extended with a diamine and / or polyamine before crosslinking with polymer B (or with the polyamine).

An advantage here is that the stability can be further improved.

Polyamines are taken to mean those compounds which have two or more primary and / or secondary amino groups. Examples of polyamines are:

Hydrazine, ethylenediamine, propylenediamine, 1,4-butylenediamine, piperazine, 4-cyclohexyldimethylamine, hexamethylenediamine-1,6, trimethylhexamethylenediamine, isophoronediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 4,4'-diaminodicyclohexylmethane and aminoethylethanolamine; and • alkylene polyamines having 1 to 40 carbon atoms, preferably having about 2 to 15 carbon atoms, having a linear or branched aliphatic, cycloaliphatic or aromatic structure and at least two primary amino groups which may have substituents which have no hydrogen atoms which are reactive with isocyanate groups ,

Polyamines to be used preferably are 2-methyldiaminopentane, ethylenediamine, N, N-diethylenetriamine, adipic acid bishydrazide and hydrazine. Adipic acid bishydrazide and hydrazine are particularly preferred. Also preferred is an embodiment of the present invention in which the diamine or polyamine has at least one group capable of forming anions. In this way it is achieved that the backbone of the and / or the polymers can contain further functional groups which enable stronger crosslinking without the stability of the dispersion being adversely affected. Because the increasing functionality of the prepolymer increases the risk of premature gelling. The introduction of the group capable of forming anions by means of the chain extender enables the group which is decisive for the stability of the dispersion to be introduced at a point in time when crosslinking of the prepolymer is not to be expected.

If the risk of gelling is to be prevented, emulsifier-free microgel dispersions are preferred in which the group capable of forming anions originates exclusively from the diamine or polyamine. Of course, other influences known to the person skilled in the art (amount and type of solvent, nature of the building blocks of the backbone and their influence on the molecular weight distribution) have a not inconsiderable influence on the risk of gelling.

If the group capable of forming anions originates exclusively from the diamine or polyamine, it is advantageous that this group capable of forming anions is a sulfonic acid group.

It is particularly preferred if at most one group capable of forming anions is present per 8,000 number-average molecular weight units. As a result, the rheological properties of the coating composition containing the emulsifier-free microgel dispersion according to the invention can be further improved.

However, the object on which the present application is based is also achieved by an emulsifier-free microgel dispersion which can be obtained by crosslinking a polymer dispersed in an aqueous medium with a blocked isocyanate, where

• the blocked isocyanate is not dispersible in water and has at least two blocked NCO groups; • the polymer has at least three groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer

• in the backbone at least one segment originating from a diol, polyol, polyether and / or a polyester polyol; and • Has at least one group capable of forming anions, and during the crosslinking the nitrogen atoms carrying at least one active hydrogen atom react with the blocked NCO groups to form urea bonds and to release the blocking agent.

This object is likewise achieved by an emulsifier-free microgel dispersion, obtainable by crosslinking a polymer dispersed in an aqueous medium with a blocked isocyanate, where

• the blocked isocyanate is not dispersible in water and has at least three blocked NCO groups;

• the polymer has at least two groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer

According to a further embodiment of the present invention, the crosslinking is carried out in the presence of an additional polymer C with an OH number between 30 and 400 and an acid number between 1 and 150, the polymer C being selected from the group of polyacrylates, polyesters and polyurethanes. In this embodiment according to the invention, the hydroxyl-containing polymer can participate in the crosslinking to the microgel.

The corresponding acid number of the additional polymer (C) is achieved by incorporating a group capable of forming anions in a manner known per se.

This embodiment leads to a further improvement in the stability and alignment of the effect pigments.

In addition, the adhesion of the coating composition containing the emulsifier-free microgel dispersion according to the invention is increased.

Suitable polyacrylates are obtainable by solution polymerization of monomers containing hydroxyl groups and alkyl (meth) acrylates, and optionally (meth) acrylic acid, styrene and / or ethylenically unsaturated monomers. Suitable monomers containing hydroxyl groups are described in detail below. All monomers with at least one polymerizable double bond, as are described in detail below, can be used as ethylenically unsaturated monomers.

Suitable polyurethanes are obtainable from the reaction of at least one diol, polyol, polyether and / or a polyester polyol with at least one polyisocyanate for the purposes of the present invention. The corresponding acid number of the polyurethane is achieved by incorporating a group capable of forming anions in a manner known per se.

According to this embodiment, the adhesion of the coating composition containing the emulsifier-free microgel dispersion according to the invention is significantly increased.

This polymer C can be added in an amount between 5 and 30% by weight, based on the solids, of the entire coating composition.

In a further, likewise preferred embodiment of the present invention, the crosslinking is carried out together with an emulsion polymerization of at least one hydroxyl group-containing monomer compound, the hydroxyl group-containing monomer compound containing at least one free-radically polymerizable double bond.

A particular advantage of such an emulsifier-free microgel dispersion lies in a further improvement in the orientation of the effect pigments, increased adhesion and improved stability.

As a result, the rheological properties of the coating composition containing the emulsifier-free microgel dispersion according to the invention can be further improved. In this embodiment, the hydroxyl group-containing monomer compound or the emulsion polymer linked via this hydroxyl group-containing monomer compound can participate in the crosslinking to form the microgel. The microgels produced in this way show no core / shell structure. The compounds mentioned above can be mentioned as monomer compounds containing hydroxyl groups and having at least one free-radically polymerizable double bond.

Are particularly preferred monomers selected from the group of 2-hydroxy propyl methacrylate, 4-hydroxybutyl acrylate and Tone ^® M 100 of Messrs. Dow Chemicals.

According to this embodiment, this monomer compound does not participate in the crosslinking to the microgel. This has a decisive positive influence on the adhesion to plastic substrates.

Such an emulsifier-free microgel, which is present in dispersion, is also present in a core / shell structure.

Partial crosslinking in the finished lacquer via the outer shell is only guaranteed if a monomer compound containing hydroxyl groups and at least one radical-polymerizable double bond is used.

By using the above-described monomer compound with at least one free-radically polymerizable double bond, the adhesion properties of the coating compositions containing the emulsifier-free microgel dispersion according to the invention can be further improved.

The use of a monomer compound without hydroxyl groups further enhances this positive adhesion property.

It should be noted that, in addition to the hydroxyl-containing acrylate monomers described above, it is also possible to use monomers which do not contain any hydroxyl groups.

Accordingly, the emulsion polymerization is carried out in the presence of at least one monomer compound without hydroxyl groups, which contains at least one free-radically polymerizable double bond. Mixtures of monomers containing hydroxyl groups and those without hydroxyl groups are particularly preferred.

Monomers with at least one free-radically polymerizable double bond which have no hydroxyl group are the compounds already mentioned above. Monomers selected from the group of the esters of acrylic or methacrylic acid and styrene are particularly preferred.

Such mixtures of monomer units with and without hydroxyl groups show excellent properties with regard to adhesion to plastic substrates without additional primer or adhesion promoter layers.

The orientation of the effect pigments is also significantly improved when using emulsifier-free microgel dispersions according to this embodiment in aqueous metallic basecoats. From a methodological point of view, this reaction has no peculiarities, but instead takes place according to the customary and known methods of radical emulsion polymerization in the presence of at least one polymerization initiator. Examples of suitable polymerization initiators are free radical initiators such as dialkyl peroxides such as di-tert-butyl peroxide or dicumyl peroxide; Hydroperoxides, such as cumene hydroperoxide or tert-butyl hydroperoxide; Peresters, such as tert-butyl perbenzoate, tert-butyl perpivalate, tert-butyl per-3,5,5-trimethyl hexanoate or tert-butyl per-2-ethyl hexanoate; Potassium, sodium or ammonium peroxodisulfate; Azodinitriles such as azobisisobutyronitrile; C-C-cleaving initiators such as benzpinacol silyl ether; or a combination of a non-oxidizing initiator with hydrogen peroxide. Water-insoluble initiators are preferably used. The initiators are preferably used in an amount of 0.1 to 25% by weight, particularly preferably 0.75 to 10% by weight, based on the total weight of the monomers (a).

Polymerization initiation by means of a redox system has proven to be particularly advantageous. This process, which is well known in emulsion polymerization technology, takes advantage of the fact that hydroperoxides are excited to free radical decomposition by suitable reducing agents even at very low temperatures. Suitable reducing agents are, for example, sodium metabisulfite or its formaldehyde addition product (Na hydroxymethanesulfinate). Is very suitable also isoascorbic acid. The combination of tert-butyl hydroperoxide, (iso) ascorbic acid and iron (II) sulfate is particularly advantageous.

The use of this mixture has the advantage that the polymerization can be started at room temperature.

The corresponding monomers are then polymerized in the solutions or the aqueous emulsions with the aid of the radical-forming initiators mentioned above at temperatures from 30 to 95 ° C., preferably 40 to 95 ° C., and when using redox systems at temperatures from 35 to 90 ° C. When working under excess pressure, the emulsion polymerization can also be carried out at temperatures above 100 ° C.

The same applies to solution polymerization if higher-boiling organic solvents and / or excess pressure are used. It is preferred that the initiator feed be started some time, generally about 1 to 15 minutes, before the monomers feed. A method is further preferred in which the initiator addition begins at the same time as the addition of the monomers and is terminated about half an hour after the addition of the monomers has ended. The initiator is preferably added in a constant amount per unit of time. After the addition of the initiator has ended, the reaction mixture is kept at the polymerization temperature (as a rule 1 to 1.5 hours) until all of the monomers used have essentially been completely reacted. "Substantially completely converted" is intended to mean that preferably 100% by weight of the monomers used have been reacted, but it is also possible that a low residual monomer content of at most up to about 0.5% by weight, based on the Weight of the reaction mixture can remain unreacted.

The reactors for the graft copolymerization are the customary and known stirred tanks, stirred tank cascades, tubular reactors, loop reactors or Taylor reactors, as described, for example, in patent specification DE 10 71 241 B1, patent applications EP 0 498 583 A1 or DE 198 28 742 A1 or in Articles by K. Kataoka in Chemical Engineering Science, Volume 50, Issue 9, 1995, pages 1409 to 1416.

According to a likewise preferred embodiment of the present invention, the polymer A and / or B • has a number average molecular weight of more than 800;

• an acid number between 10 and 70 mg KOH / g; on. According to the state of knowledge to date, the number average molecular weight has a considerable influence on the rheology of the coating composition containing the emulsifier-free microgel dispersion according to the invention. In general, a higher number average molecular weight causes an increase in the crosslinking points within the microgel (ie the mesh size of the polymer is increased).

It is important here, however, that even with a high number-average molecular weight, sufficient stability of the dispersion is ensured with a degree of neutralization sufficient for stabilization in water.

The diol or polyol, which can be found as a corresponding segment in the backbone of the polymer A and / or B, is preferably a diol and / or polyol with 2 to 36 carbon atoms in the sense of the present invention, which is preferably selected is from the group of trimethylolpropane monoallyl ether, di-trimethylolpropane and hydroxylated fatty acid compounds.

By using polyols, i.e. of compounds with more than three OH groups, a higher functionality of the prepolymer is also ensured here, so that an increased crosslinking is achieved, which is shown in improved rheological properties of the coating compositions containing these microgel dispersions.

The polyester polyol used for the present invention is a compound which is obtainable from the polycondensation of at least one diol and / or polyol with at least one polycarboxylic acid or its anhydride. Examples of suitable polycarboxylic acids are aromatic, aliphatic and cycloaliphatic polycarboxylic acids. Aromatic and / or aliphatic polycarboxylic acids are preferably used.

Examples of suitable aromatic polycarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic acid, isophthalic acid or terephthalic acid monosulfonate, or halophthalic acids, such as tetrachloro- or tetrabromophthalic acid, of which isophthalic acid and trimellitic acid anhydride are preferably used, and therefore trimellitic acid anhydride is preferably used.

Examples of suitable acyclic aliphatic or unsaturated polycarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid or dimer fatty acid or maleic acid, fumaric acid, adasic acid, sebacic acid, or adipic acid, or adipic acid, or adipic acid, or adipic acid, or adipic acid, or adipic acid, sorbic acid, Dimer fatty acids and maleic acid are advantageous and are therefore used with preference. Examples of suitable cycloaliphatic and cyclic 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, tetrahydrophthalic acid or 4-methyltetrahydrophthalic acid. These dicarboxylic acids can be used both in their ice and in their trans form and as a mixture of both forms.

The transesterifiable derivatives of the above-mentioned polycarboxylic acids, such as e.g. their mono- or polyvalent esters with aliphatic alcohols with 1 to 4 carbon atoms or hydroxy alcohols with 1 to 4 carbon atoms. In addition, the anhydrides of the above-mentioned polycarboxylic acids can also be used if they exist.

If necessary, monocarboxylic acids, such as, for example, benzoic acid, tert-butylbenzoic acid, lauric acid, isononanoic acid, fatty acids of naturally occurring oils, acrylic acid, methacrylic acid, ethacrylic acid or crotonic acid can also be used together with the polycarboxylic acids. Isononanoic acid is preferably used as the monocarboxylic acid.

Examples of suitable polyols are diols and triols, especially diols. In addition to the diols, triols are usually used in minor amounts in order to introduce branches into the polyester polyols. 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-pentanediol, 1, 2-, 1, 3-, 1, 4-, 1,5- or 1,6-hexanediol, hydroxypivalic acid neopentyl ester, neopentyl glycol, diethylene glycol, 1, 2-, 1, 3- or 1, 4-cyclohexanediol, 1, 2-, 1, 3- or 1, 4-cyclohexanedimethanol, trimethylpentanediol, ethylbutylpropanediol, the positionally isomeric diethyloctanediols, 2-butyl-2-ethylpropanediol-1, 3, 2-butyl-2- methylpropanediol-1,3,2-phenyl-2-methylpropanediol-1,3,2-propyl-2-ethylpropanediol-1,3,2-di-tert-butylpropanediol-1,3,2-butyl-2 -propylpropanediol-1, 3, 1-dihydroxymethyl-bi-cyclo [2.2.1] heptane, 2,2-diethylpropanediol-1,3, 2,2-dipropylpropanediol-1, 3, 2-cyclohexyl-2-methylpropanediol -1, 3, 2,5-dimethyl-hexanediol-2,5, 2,5-diethylhexanediol-2,5, 2-ethyl-5-methylhexanediol-2,5, 2,4-dimethylpentanediol-2,4 , 2,3-dimethylbutanediol-2,3,1,4- (2'-hydroxypropyl) benzene or 1,3- (2'-hydroxypropyl) benzene. Of these diols, 1, 6-hexanediol and neopentyl glycol are particularly advantageous and are therefore used with particular preference.

Higher functional polyols such as trimethylolpropane, glycerol, pentaerythritol, di-trimethylolpropane and di-pentaerythritol can also be used. Further examples of suitable polyols are polyester diols which are obtained by reacting a lactone with a diol. They are characterized by the presence of terminal hydroxyl groups and recurring polyester components of the formula - (- CO- (CHR) _m -CH ₂ -O -) -. Here, the index m is preferably 4 to 6 and the substituent R = hydrogen, an alkyl, cycloalkyl or alkoxy radical. No substituent contains more than 12 carbon atoms. The total number of carbon atoms in the tuenten does not exceed 12 per lactone ring. Examples include hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid and / or hydroxystearic acid. For the preparation of the polyester diols, the unsubstituted ε-caprolactone, in which m is 4 and all R substituents are hydrogen, is preferred. The reaction with lactone is started by low molecular weight polyols such as ethylene glycol, 1,3-propanediol, 1, 4-butanediol or dimethylolcyclohexane. However, other reaction components, such as ethylenediamine, alkyldialkanolamines or urea, can also be reacted with caprolactone. Also suitable as higher molecular weight diols are polylactam diols which are prepared by reacting, for example, ε-caprolactam with low molecular weight diols.

Further examples of suitable polyols are polyether polyols, in particular with a number average molecular weight from 400 to 5,000, in particular from 400 to 3,000. Highly suitable polyether polyols are, for example, polyether diols of the general formula H - (- O- (CHR) o-) pOH, where the substituent R = hydrogen or a lower, optionally substituted alkyl radical, the index o = 2 to 6, preferably 3 to 4 , and the index p = 2 to 100, preferably 5 to 50. Linear or branched polyether diols such as poly (oxyethylene) glycols, poly (oxypropylene) glycols and poly (oxybutylene) glycols are mentioned as particularly suitable examples. On the one hand, the polyether diols should not introduce excessive amounts of ether groups, because otherwise the polyurethanes formed to be used according to the invention swell in water. On the other hand, they can be used in amounts which ensure the nonionic stabilization of the polyurethanes. They then serve as the functional nonionic groups (a3) described below. Further examples of suitable polyols are poly (meth) acrylate diols, polycarbonate diols or polyolef in polyols such as POLYTAIL ^® from the Mitsubishi Chemical Group. In a preferred embodiment, the polyester polyol has a number average molecular weight between 200 and 6,000, an OH number between 20 and 550 and an acid number less than 5. Particularly good results with regard to advantageous crosslinking - suitable for the use of the emulsifier-free microgels according to the invention in coating compositions - are achieved if in the backbone of polymer A and / or B from different OH-functional compounds, ie from different diols, polyols, polyethers and / or a polyester polyol, originating segments are present.

This crosslinking then also has a decisive influence both on the adhesion, the orientation of the effect pigments, the stability and the rheology of the coating composition containing the emulsifier-free microgel dispersion according to the invention. For example, by selecting a suitable low molecular weight polyol and a long-chain, linear polyester polyol, a high crosslinking density is achieved, the distance between the respective crosslinking centers being sufficiently high without the rheological properties and the adhesion of a coating composition containing the emulsifier-free microgel dispersion according to the invention would no longer be guaranteed in this case.

In a particularly preferred embodiment of the present invention, the group capable of forming anions originates from dimethylolpropionic acid and / or 9,10-dihydroxystearic acid. These specially selected compounds give the dispersion significantly improved stability.

According to a further, likewise preferred embodiment of the present invention, the group capable of forming anions originates from a polyester polyol which, on a statistical average, has at least one free carboxyl group per molecule which originates from trimellitic acid, trimellitic anhydride, dimethylolpropionic acid or dihydroxystearic acid.

Here, too, the functionality which is decisive for the stability of the dispersion is introduced via an additional connection, so that the risk of gelling during the preparation of the prepolymer is prevented and at the same time an increased functionality of the prepolymer building blocks is achieved.

Emulsifier-free microgel dispersion according to one of the preceding claims, characterized in that at least one of the groups having at least one active hydrogen atom of the polymer bound to a nitrogen atom is composed of a di or polyamine, in particular of 2-methyldiaminopentane, ethylenediamine, N, N-diethylenetriamine, Adipic acid bishydrazide or hydrazine segment.

Hydrazine and adipic acid bishydrazide are particularly preferably used as polyamines for the purposes of the present invention.

Adducts from the reaction of the polyamines described above with one or more monomers with at least one vinyl double bond by Michael addition can also be used.

Suitable monomers with at least one vinyl double bond are esters of acrylic or methacrylic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, isopropyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, α-ethylhexyl (meth) acrylate, furfuryl (meth) acrylate, octyl (meth) acrylate, 3.5 , 5-trimethylene hexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, stearyl (meth) acrylate and ethyl triglycol (meth) acrylate; Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate. The blocked NCO groups, identical or different, originate from the reaction with a compound, which in turn results from the reaction of a polyisocyanate with a suitable capping agent. The term "blocking agent" is synonymous with the term "capping agent".

All compounds which are used in the production of water-dilutable basecoats are suitable as polyisocyanates. The above-mentioned isocyanate compounds should be mentioned as examples of such polyisocyanates. Particularly good results are obtained with 1,1-methylenebis (4-isocyanatocyclohexane), (4,4'-dicyclohexylmethane diisocyanate, Desmodur W), hexamethylene diisocyanate (HMDI, 1,6-diisocyanatohexane, Desmodur H), isophorone diisocyanate (IPDI, 3,5, 5-TrimethyM-isocyanato-3-isocyanatomethylcyclohexane), 1, 4-cyclohexyl diisocyanate (CHDI, trans, - trans-1, 4-diisocyanatocyclohexane), N-isocyanatohexylaminocarbonyl-N, N'-bis (isocyanate hexyl) urea (Desmodur N ), 2,4,6-trioxo-1,3,5-tris (6-isocyanatohexyl) hexa- hydro-1,3,5-triazine (Desmodur N3300), 2,4,6-trioxo-1,3. 5-tris (5-isocyanato-1,3,3-trimethylcyclohexylmethyl) hexahydro-1,3,5-triazine (Desmodur Z4370). The use of TMXDI (m-tetramethylxylylenediisocyanate), which introduces the blocked NCO groups after reaction with a blocking agent, is very particularly preferred. The term "capping agent" is understood to mean those compounds which react with the NCO groups of a polyisocyanate in such a way that the polyisocyanate capped in this way is resistant to hydroxyl groups at room temperature. At elevated temperatures, generally in the range of about 90 up to 300 ° C, the capped polyisocyanate reacts with elimination of the capping agent.

Any suitable aliphatic, cycloaliphatic or aromatic alkyl monoalcohols can be used for the capping (or also blocking) of the polyisocyanates. Examples include aliphatic alcohols such as methyl, ethyl, chloroethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl, 3,3,5-trimethylhexyl, decyl and lauryl alcohol ; aromatic alkyl alcohols, such as phenylcarbinol and methylphenylcarbinol. Small proportions of higher molecular weight and relatively poorly volatile monoalcohols can optionally also be used, these alcohols acting as plasticizers in the coatings after they have been split off. Other suitable capping agents are oximes, such as methyl ethyl ketone oxime, acetone oxime and cyclohexanone oxime, as well as caprolactams, phenols and hydroxy formic acid esters. Preferred capping agents are malonic esters, acetoacetic esters and β-diketones. The capped polyisocyanates are prepared by reacting the capping agent in sufficient quantities with the organic polyisocyanate so that no free isocyanate groups are present.

Examples of suitable blocking agents are the compounds mentioned above.

In the context of the embodiment of the present invention, methyl ethyl ketoxime is particularly preferred as the capping agent.

In order to counter the risk of gelling, the previously described polyisocyanates can be partially capped. This means the reaction of the polyisocyanate with a capping agent in deficit.

The object is also achieved according to the invention by an emulsifier-free and acrylate-modified microgel dispersion, obtainable by emulsion polymerization of at least one hydroxyl-containing monomer compound (A) which contains at least one free-radically polymerizable double bond, in the presence of an aqueous dispersion of a polymer (B), the latter containing

• at least two blocked NCO groups; • in the backbone of the prepolymer at least one segment originating from a diol, polyol, polyether and / or polyester polyol; and

• at least one group capable of forming anions, during which the hydroxyl groups of the monomer compound (A) react with the blocked NCO groups of the polymer (B) to form urethane bonds and release the blocking agent during the emulsion polymerization.

In principle, two major reactions are also involved in this implementation: First, decapping takes place, ie the blocked NCO groups are converted into free NCO groups with the release of the capping agent. These free NCO groups react with the corresponding other hydroxyl-containing components present in the reaction mixture, in particular with the hydroxyl-containing monomer compound (A). On the other hand, the hydroxyl group-containing monomer compound (A) is polymerized, ie, a so-called polymer-analogous reaction. According to a preferred embodiment of the present invention, the emulsion polymerization is additionally carried out in the presence of at least one hydroxyl-free monomer compound (C) which contains at least one free-radically polymerizable double bond.

As a result, the networking points are scattered and are subject to statistical distribution.

Monomers (C) with at least one free-radically polymerizable double bond which have no hydroxyl group are the unsaturated compounds already described above.

According to a further embodiment of the present invention, the crosslinking is carried out in the presence of an additional polymer (D) with an OH number between 30 and 400 and an acid number between 1 and 150, the polymer (D) being selected from the group of Polyacrylates, polyesters and polyurethanes.

In this embodiment according to the invention, the hydroxyl-containing polymer can participate in the crosslinking to the microgel. If this polymer (D) is water-dilutable, this polymer (D) is dispersed in water after the solution polymerization under the measures known per se. Otherwise, a premix is formed from the non-water-dilutable polymer (D) together with the non-water-dispersed polymer (B), which is then subjected to dispersion in water. The polymer (D) can be added in an amount between 5 and 30% by weight, based on the solids, of the entire coating composition.

The corresponding acid number of the polyacrylate is achieved by incorporating a group capable of forming anions in a manner known per se.

The corresponding acid number of the polyester is achieved by incorporating a group capable of forming anions in a manner known per se.

Furthermore, in a further, likewise preferred embodiment, the present invention relates to an emulsifier-free microgel dispersion in which the reaction mixture originating from the crosslinking is subsequently subjected to a further emulsion polymerization with at least one monomer compound, the monomer compound containing at least one free-radically polymerizable double bond.

This monomer compound with at least one radical-polymerizable double bond is particularly preferably hydroxyl-containing.

The compounds already mentioned above may be mentioned as monomer compounds containing hydroxyl groups and having at least one free-radically polymerizable double bond.

Such an emulsifier-free microgel, which is present in dispersion, is present in a core / shell structure. The inner area is largely networked according to the definition given above. However, the outer area of this core / shell microgel is not networked. The outer shell is crosslinked when in use of a monomer compound with at least one free-radically polymerizable double bond only under baking conditions for the production of corresponding multi-layer coatings.

Partial crosslinking in the finished lacquer via the outer shell is only guaranteed if a hydroxyl group-containing monomer compound with at least one radical-polymerizable double bond is also used.

According to this embodiment, the polymerized monomer compound does not participate in the crosslinking to the microgel. In addition, a coating composition containing this emulsifier-free microgel dispersion exhibits such excellent adhesion that it can also be used in multi-layer coatings, which are considered critical, in particular in conjunction with powder clearcoats, in automotive series coating. In the core / shell polymers or microgels described above, according to a preferred embodiment, only those monomers with at least one free-radically polymerizable double bond are used which do not contain any hydroxyl groups.

Such an emulsifier-free microgel, which is present in dispersion, is present in a core / shell structure. The inner area is largely networked according to the definition given above. The outer area of this core / shell microgel is also not networked. In contrast to the core / shell polymer described above, the outer shell cannot be crosslinked under baking conditions for the production of appropriate multi-layer coatings.

The orientation of the effect pigments is significantly improved when using emulsifier-free microgel dispersions according to this embodiment in aqueous metallic basecoats. From a methodological point of view, this reaction has no peculiarities, but instead takes place according to the customary and known methods of radical emulsion polymerization in the presence of at least one polymerization initiator. Examples of suitable polymerization initiators are the 3 compounds already mentioned above. Water-insoluble initiators are preferably used. The initiators are preferably used in an amount of 0.1 to 25% by weight, particularly preferably 0.75 to 10% by weight, based on the total weight of the monomers (a). One possibility of initiating polymerization by means of a redox system is also described above.

The same applies to solution polymerization if higher-boiling organic solvents and / or excess pressure are used.

It is preferred that the initiator feed be started some time, generally about 1 to 15 minutes, before the monomers feed. Furthermore, a method is preferred in which the initiator addition begins at the same time as the addition of the monomers and is ended about half an hour after the addition of the monomers has ended. The initiator is preferably added in a constant amount per unit of time. After the initiator addition has ended, the reaction mixture is kept at the polymerization temperature (as a rule 1 to 1.5 hours) until all of the monomers used have essentially been completely reacted. "Substantially completely converted" is intended to mean that preferably 100% by weight of the monomers used have been reacted, but it is also possible that a low residual monomer content of at most up to about 0.5% by weight, based on the Weight of the reaction mixture can remain unreacted.

Suitable reactors for the graft copolymerization are the customary and known reactors already mentioned above. According to a likewise preferred embodiment of the present invention, the polymer A

• a number average molecular weight of more than 800;

• an acid number between 20 and 150 mg KOH / g; on.

According to the state of knowledge to date, the number average molecular weight has a considerable influence on the rheology of the coating composition containing the emulsifier-free microgel dispersion according to the invention. In general, a higher number average molecular weight causes an increase in the crosslink points within the microgel (i.e. the mesh size of the polymer is increased).

It is important here, however, that even with a high number average molecular weight, the dispersion is sufficiently stable with a degree of neutralization sufficient for stabilization in water.

According to a preferred embodiment of the present invention, a diol and / or polyol having 2 to 36 carbon atoms is used as the diol or polyol, which can be found as a corresponding segment in the backbone of the polymer (B).

Examples of diols for this 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-pentanediol, 1, 2-, 1, 3-, 1,4-, 1,5- or 1, 6-hexanediol, hydroxypivalic acid neopentyl ester, neopentyl glycol, diethylene glycol, 1, 2-, 1,3- or 1, 4-cyclohexanediol, 1, 2-, 1, 3- or 1, 4-cyclohexanedimethanol, trimethylpentanediol, ethylbutylpropanediol, the positionally isomeric diethyloctanediols, 2-butyl-2-ethylpropanediol-1, 3, 2-butyl- 2-methyl propanediol-1, 3, 2-phenyl-2-methyl propanediol-1, 3, 2-propyl-2-ethyl propanediol-1, 3, 2-di-tert-butyl propanediol-1, 3, 2-butyl -2-propylpropanediol-1, 3, 1 -dihydroxymethyl-bi-cyclo [2.2.1] heptane, 2,2-diethylpropanediol-1, 3, 2,2-dipropylpropanediol-1, 3, 2-cyclohexyl-2 -methylpropanediol-1, 3, 2,5-dimethyl-hexanediol-2,5, 2,5-diethylhexanediol-2,5, 2-ethyl-5-methylhexanediol-2,5, 2,4-dimethylpentanediol-2,4 , 2,3-dimethylbutanediol-2,3, 1,4- (2'-hydroxypropyl) benzene, 1,3, (2'-hydroxypropyl) benzene or dimer diol (Un ichema).

Trimethylolpropane, glycerol, pentaerythritol, di-trimethylolpropane, di-pentaerythritol and hydroxylated, epoxidized linseed or soybean oils are to be mentioned as polyols for this purpose.

The diol or polyol is preferably selected from the group of 1,6-hexanediol and di-trimethylolpropane.

In particular, the use of polyols (ie compounds with more than three OH groups) also results in a higher functionality of the prepolymer. ensures that increased crosslinking is achieved, which is reflected in improved rheological properties of the coating compositions containing these microgel dispersions.

Examples of suitable aromatic polycarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic acid, isophthalic acid or terephthalic acid monosulfonate, of which isophthalic acid and trimellitic anhydride are advantageous and are therefore used with preference.

Examples of suitable acyclic, aliphatic or unsaturated polycarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, or dimer fatty acids or maleic acid, fumaric acid or itaconic acid, of which adipic acid, glutaric acid, azelaic acid, sebacic acid ; whereby dimer fatty acids are advantageous and are therefore preferably used.

Examples of suitable cycloaliphatic and cyclic 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 Methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid, tetrahydrophthalic acid or 4-methyltetrahydrophthalic acid. These dicarboxylic acids can be used both in their ice and in their trans form and as a mixture of both forms. Also suitable are the transesterifiable derivatives of the abovementioned polycarboxylic acids, such as, for example, their mono- or polyvalent esters with aliphatic alcohols with 1 to 4 carbon atoms or hydroxy alcohols with 1 to 4 carbon atoms. In addition, the anhydrides of the above-mentioned polycarboxylic acids can also be used if they exist. If necessary, monocarboxylic acids, such as, for example, benzoic acid, tert-butylbenzoic acid, lauric acid, isononanoic acid, fatty acids of naturally occurring oils, acrylic acid, methacrylic acid, ethacrylic acid or crotonic acid can also be used together with the polycarboxylic acids. In addition to the diols, triols are usually used in minor amounts in order to introduce branches into the polyester polyols.

1, 6-Hexanediol and neopentyl glycol are particularly advantageous as diols and are therefore used with particular preference. Further examples of suitable polyols are polyester diols which are obtained by reacting a lactone with a diol. They are characterized by the presence of any hydroxyl groups and recurring polyester components of the formula - (- CO- (CHR) _m -CH ₂ -O -) -. Here, the index m is preferably 4 to 6 and the substituent R = hydrogen, an alkyl, cycloalkyl or alkoxy radical. No substituent contains more than 12 carbon atoms. The total number of carbon atoms in the substituent does not exceed 12 per lactone ring. Examples include hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid and / or hydroxystearic acid. For the preparation of the polyester diols, the unsubstituted ε-caprolactone, in which m is 4 and all R substituents are hydrogen, is preferred. The reaction with lactone is started by low molecular weight polyols such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol or dimethylolcyclohexane. However, other reaction components, such as ethylenediamine, alkyldialkanolamines or urea, can also be reacted with caprolactone. Also suitable as higher molecular weight diols are polylactam diols, which are produced by reacting, for example, ε-caprolactam with low molecular weight diols.

Further examples of suitable polyols are the polyether polyols described above. On the one hand, the polyether diols should not introduce excessive amounts of ether groups, because otherwise the polyurethanes formed to be used according to the invention swell in water. On the other hand, they can be used in amounts which ensure the nonionic stabilization of the polyurethanes.

Further examples of suitable polyols are poly (meth) acrylate diols, polycarbonate diols or polyolefin polyols such as POLYTAIL ^® from the Mitsubishi Chemical Group.

According to a further, likewise preferred embodiment of the present invention, the polyester polyol has a number average molecular weight between 200 and 6,000, an OH number between 20 and 550 and an acid number less than 5.

Particularly good results with regard to advantageous crosslinking - suitable for the use of the emulsifier-free microgels according to the invention in coating compositions - are achieved if in the backbone of the polymer (B) from different OH-functional compounds, ie from different diols, polyols, polyethers and / or a polyester polyol , originating segments are present. This crosslinking then also has a decisive influence both on the adhesion, the orientation of the effect pigments, the stability and the rheology of the coating composition containing the emulsifier-free microgel dispersion according to the invention. Here too, a high crosslinking density can be achieved by choosing a suitable low molecular weight polyol and a long-chain, linear and / or branched polyester polyol, the distance between the respective crosslinking centers being sufficiently high that the rheological properties are positively influenced.

In a particularly preferred embodiment of the present invention, the group capable of forming anions originates from dimethylolpropionic acid and / or 9,10-dihydroxystearic acid.

According to a further, likewise preferred embodiment of the present invention, the group capable of forming anions originates from a polyester polyol which on average has at least one free carboxyl group per molecule which originates from trimellitic acid, trimellitic anhydride, dimethylolpropionic acid or dihydroxy-stearic acid.

Here, too, the functionality which is decisive for the stability of the dispersion is introduced via an additional compound, so that the risk of gelling during the preparation of the prepolymer is reduced and at the same time an increased functionality of the prepolymer building blocks is achieved.

The blocked NCO groups, identical or different, originate from the reaction with a compound, which in turn results from the reaction of a polyisocyanate with a suitable capping agent. The term "blocking agent" is synonymous with the term "capping agent". All compounds which are used in the production of water-dilutable basecoats are suitable as polyisocyanates. Examples of such polyisocyanates have already been mentioned above.

Particularly good results are obtained with 1,1-methylenebis (4-isocyanatocyclohexane), (4,4'-dicyclohexylmethane diisocyanate, Desmodur W), hexamethylene diisocyanate (HMDI, 1,6-diisocyanatohexane, Desmodur H), isophorone diisocyanate (IPDI, 3,5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane), 1, 4-cyclohexyldiisocyanate (CHDI, trans, - trans-1, 4-diisocyanatocyclohexane), N-isocyanatohexylaminocarbonyl-N, N'-bis (isocyanatehexyl) urea ( Desmodur N), 2,4,6-trioxo-1, 3,5-tris (6-isocyanatohexyl) hexa- hydro-1,3,5-triazine (Desmodur N3300), 2,4,6-trioxo-1,3,5-tris (5-isocyanato-1,3,3-trimethylcyclohexylmethyl) hexahydro-1,3. 5-triazine (Desmodur Z4370) achieved. The use of TMXDI (m-tetramethylxylylenediisocyanate), which introduces the blocked NCO groups after reaction with a blocking agent, is very particularly preferred.

The term “capping agent” is understood to mean compounds which react with the NCO groups of a polyisocyanate in such a way that the polyisocyanate capped in this way is resistant to hydroxyl groups at room temperature. At elevated temperatures, generally in the range from about 90 to 300 ° C, the capped polyisocyanate reacts with elimination of the capping agent.

Any suitable aliphatic, cycloaliphatic or aromatic alkyl monoalcohols, as already described above, can be used for the capping (or also blocking) of the polyisocyanates.

Preferred capping agents are malonic esters, acetoacetic esters and β-diketones. The capped polyisocyanates are produced by reacting the capping agent with the organic polyisocyanate in sufficient quantity so that there are no longer any free isocyanate groups.

In order to counter the risk of gelling here, too, the polyisocyanates described above can be partially capped.

In addition to the previously described embodiments, the microgel in its backbone can also have other structural units or segments that originate from the usual starting components used in paint chemistry. For example, the polymer A may contain polyurethane segments which originate from the previously described, uncapped polyisocyanates and compounds containing hydroxyl groups (e.g. diols, polyester polyols, polether).

According to a preferred embodiment, the number average molecular weight of polymer A is at most 10,000, preferably between 1,000 and 8,000.

This achieves an optimal range for a sufficiently high degree of crosslinking with a sufficiently large mesh size. According to a further, likewise preferred form of the invention, the microgel has an acid number between 10 and 50 mg KOH / g, in particular between 10 and 30 mg KOH / g.

On the one hand, sufficient stability in water and on the other hand not excessively high hydrophilicity is achieved, i.e. the resulting paints do not show insufficient resistance to condensation.

According to the invention, the emulsifier-free microgel dispersion described above is particularly suitable for producing a multilayer coating, in particular in the automotive industry.

The use of the emulsifier-free microgel dispersion in the coloring coating composition, i.e. in a basecoat.

The best results in terms of rheological, mechanical and optical properties are achieved if the proportion of microgel, based on the solids content of the layer obtainable therefrom, is between 20 and 85%, preferably between 20 and 65%. It is also surprising that the emulsifier-free microgel dispersions according to the invention can be used in addition to the conventional sheet silicates in water-dilutable basecoats. In this case, the resulting paint films do not show insufficient resistance to condensation.

For the use according to the invention, the multi-layer coating can consist of three different layers, i.e. out

1) a first layer of an electrophoretically deposited coating agent located on the electrically conductive substrate;

2) a second, color-providing layer, obtainable from a water-dilutable coating composition, which contains the emulsifier-free microgel dispersion according to the invention; and

3) a third layer of clear varnish.

In the case of this multi-layer coating comprising in particular only three layers which are different from one another, it should be emphasized that the resulting multi-layer coating also has sufficient stone chip resistance, which is attributable to the special properties of the water-dilutable basecoat containing the emulsifier-free microgel of the present invention. It is also possible that the multi-layer coating consist of four different layers, ie of

2) a second layer of primer or filler;

3) a third, color-imparting layer, obtainable from a water-dilutable coating composition, which contains the emulsifier-free microgel dispersion according to the invention; and

4) a fourth layer of a clear lacquer.

An advantage in this four-layer structure is that the hardened coloring layer has a further positive effect on the stone chip protection properties of the filler layer.

By using the emulsifier-free microgel according to the invention, a significantly higher layer thickness can be achieved, based on conventional basecoats. The thickness of the cured layer produced from a coating composition containing the emulsifier-free microgel dispersion according to the invention can be between 15 and 55 μm.

The coating agents to be deposited electrophoretically are aqueous coating compositions with a solids content of about 10 to 20% by weight, which usually carry binders, ionic or ionic substituents and groups capable of chemical crosslinking, and also contain pigments and other customary additives , Examples of such electrocoat materials are in DE 28 24 418 A1, DE 33 24 211 A1, EP 0 082 291, EP 0 178 531, EP 0 227 975, EP 0 234 395, EP 0 245 786, EP 0 261 385, EP 0 310 971, EP 0 333 327, EP 0 414 199, EP 0 456 270, EP 0 476 514 and US 3 922 253.

The clear lacquer layer, which is arranged above the color-imparting basecoat layer in a multilayer coating for automobiles, can be obtained by applying and baking a customary, solvent-containing or aqueous clear-coating composition which is present as a one-component or two-component mixture and contains one or more base resins as film-forming binders. If the binders are not self-crosslinking, the clear lacquer composition can optionally also contain crosslinking agents. Polyester, polyurethane and / or poly (meth) acrylate resins, for example, can be used as film-forming binders (base resins). In addition to the chemically crosslinking binders and, if appropriate, crosslinking agents, these clearcoats can contain customary paint auxiliaries, such as, for example, catalysts, leveling agents and light stabilizers.

Examples of solvent-containing clear lacquer compositions in one-component or two-component mixtures are in DE 38 26 693 A1, DE 40 17 075 A1, DE 41 24 167 A1, DE 41 33 704 A1, DE 42 04 518 A1, DE 42 04 611 A1, EP 0 257 513, EP 0 408 858, EP 0 523 267 and EP 0 557 822.

Examples of aqueous clear lacquer compositions in one-component or two-component mixtures are in DE 39 10 829 A1, DE 40 09 931 A1, DE 40 09 932 A1, DE 41 01 696 A1, DE 41 32 430 A1, DE 41 34 290 A1, DE 42 03 510 A1, EP 0 365 098, EP 0 365 775, EP 0 469 079 and EP 0 546 640, in particular in DE 44 19 216 A1 and DE 44 42 518 A1.

The clear lacquer layer can also be produced from a powder clear lacquer or a powder clear lacquer slurry.

With regard to the powder clearcoat or powder clearcoat slurry, reference is made to DE 42 22 194 A1, DE 42 27 580 A1, EP 0 509 392, EP 0 509 393, EP 0 522 648, EP 0 544 206, EP 0 555 705, EP 0 652 265, EP 0 666 779 and EP 0 714 958.

However, it is also possible to convert the microgel dispersion according to the invention into a non-aqueous phase and to use it in coating compositions containing solvents.

In order to obtain microgels in the non-aqueous phase, the water must be removed from the microgels according to the invention which are present in the aqueous phase. This can be done by any known method, for example by spray drying, freeze drying or evaporation, if appropriate under reduced pressure.

After dehydration, the microgel according to the invention can be in powder form or as a resinous mass.

According to a preferred variant, the microgel present in the aqueous phase is converted into a liquid organic phase. This can be done by azeotropic distillation. The procedure here can be such that the aqueous, emulsifier-free microgel dispersion is introduced continuously or discontinuously into a reactor at elevated temperature, optionally under reduced pressure, which contains an entrainer, i.e. a solvent or a mixture of several solvents, at least one of which forms an azeotrope with water.

The reactor is equipped with a suitable condensing device and a water separator with a return to the reactor. After reaching the boiling point During the azeotrope, the gaseous azeotropic phase (ie entrainer and water) rises into the condensing device. The azeotrope condenses there and runs from there into the water separator. In the water separator there is a phase separation between the entrainer and the water. When azeotropic distillation is carried out continuously, the entrainer flows back into the reactor, so that only small amounts of entrainer have to be used. The water obtained from the water separator is free from organic constituents and can be used again to produce the aqueous microgel dispersion according to the invention. The entrainer can be selected from the group of xylene, butyl acetate, methyl isobutyl ketone, methyl amyl ketone, pentanol, hexanol or ethyl hexanol. A major advantage here is that the entrainer remains there after the conversion into the organic phase and is advantageous for the use of solvent-containing coating compositions. With regard to the further use of these microgels present in the organic phase for the production of solvent-containing coating compositions, the aforementioned entraining agents are suitable solvents.

Due to the simultaneous reuse of the entrainer and the water obtained without additional process steps, this process is characterized by an extraordinary degree of environmental compatibility, since no by-products to be disposed of are produced which are produced in large quantities in comparison with known production processes.

In a special form of azeotropic distillation, this is carried out in such a way that the aqueous emulsifier-free microgel dispersion is added to a mixture of an entrainer and a high-boiling organic solvent. This high-boiling, organic solvent prevents caking of the microgels on the wall of the reactor during the conversion into the organic phase. The high-boiling solvent can be selected from the group of glycol esters, e.g. Butyl glycol acetate and / or butyl diglycol acetate may be selected.

As in the case of the entrainer, the high-boiling solvent is also a component customary for a solvent-containing coating composition.

The microgel obtainable in this way can be used in particular for solvent-containing coating compositions.

A preferred form of use of the invention is the use in solvent-borne basecoats, in particular effect basecoats and clearcoats, for the topcoating or painting of automobiles. This microgel, which is in the organic phase, also gives these solvent-containing coating compositions excellent application behavior and outstanding decorative properties, which can be demonstrated, for example, by a pronounced metallic effect, very good resistance to vertical runoff (SCA - Sagging Control Agent), freedom from clouds, resistance to reactivation Solve with clear varnish, good sanding groove coverage and the fulfillment of the property specifications common in the automotive industry.

The microgels can also be used for the production of solventborne clearcoats, coil coating compositions and stoving lacquers for industrial applications as well as paints for the construction sector.

Another special feature of this microgel is its high shear resistance. This property makes it possible for the first time to use such microgels for the production of pigment preparations, in particular as a grinding agent for tinting pastes. This ensures that the tinting pastes thus produced have a high pigment content with a low viscosity at the same time.

EXAMPLES:

Production of the starting products

Polyester 1: In a 4 liter reaction vessel with stirrer and packed column 722.7 g of 1, 6 hexane diol, and 2621, 2 g of a dimerized fatty acid (Pripol ^® 1013 of the firm Uni chema) was weighed and heated such that the column head temperature 100 ° C does not exceed. The max. Esterification temperature is 230 ° C. If the acid number is below 3, the mixture is cooled. A polyester with a calculated molecular weight of 2000 and a hydroxyl number of 56 is obtained.

Polyester 2:

In a 2 liter reaction vessel with stirrer and packed column, 47.2 g of 1.6 hexanediol, 167.5 g of trimethylolpropane, 60.9 g of trimethylolpropane monoallyl ether, 111 g of phthalic anhydride and 350 g of an isomerized soybean fatty acid are weighed out and heated so that the column top temperature is 100 ° C does not exceed. The max. Esterification temperature is 230 ° C. If the acid number is below 10, the mixture is cooled to 150 ° C. 144 g of trimellitic anhydride are added at 150 ° C. and thus heats that the column head temperature does not exceed 100 ° C. The max. Esterification temperature is 180 ° C. At an acid number of 51, the mixture is cooled and diluted with 146 g of methyl ethyl ketone. A polyester with a solids content of 85% is obtained (60 minutes at 120 ° C.).

Polyester 3:

In a 4 l reaction vessel with stirrer and packed column, 1274.4 g of 1, 6 hexanediol and 1593.6 g of isophthalic acid are weighed out and heated in such a way that the column top temperature does not exceed 100.degree. The max. Esterification temperature is 230 ° C. If the acid number is below 3, the mixture is cooled. A polyester with a calculated molecular weight of 2100 and a hydroxyl number of 53 is obtained.

Polyester 4:

660.8 g 1, 6 hexanediol, 531, 2 g isophthalic acid and 153.6 g trimellitic anhydride are weighed in a 2 l reaction vessel with stirrer and packed column and heated so that the column top temperature does not exceed 100.degree. The max. Esterification temperature is 230 ° C. If the acid number is below 3, the mixture is cooled and diluted with 502 g of methyl ethyl ketone. A polyester with a solids content of 71% is obtained (60 minutes at 120 ° C.).

Polyester 5:

In a 4 l reaction vessel with stirrer and packed column 1252.8 g of a dimerized fatty acid (Pripol ^® 1013 from Unichema), 669.1 g of 1, 6-hexanediol and 493 g of isophthalic acid are not weighed out and heated so that the column head temperature 100 ° C exceeds. The max. Esterification temperature is 230 ° C. If the acid number is below 3, the mixture is cooled and diluted with 860 g of methyl ethyl ketone. A polyester with a solids content of 74% (60 minutes at 120 ° C.) is obtained.

Acrylate dispersion 1 (for application examples): 200 g of butylglycol are weighed into a 4 l reaction vessel with a stirrer and an inlet vessel and heated to 120.degree. At 120 ° C., a mixture of 285 g of methyl methacrylate, 140 g of 2-ethylhexyl acrylate, 60 g of 2-hydroxypropyl methacrylate, 15 g of methacrylic acid and 10 g of tert-butyl per-2-ethylhexanoate is uniformly metered in from the feed vessel over the course of 3 hours. After the end of the feed, polymerization is continued for 0.5 hours. A mixture of 10 g of butyl glycol and 1 g of tert-butyl per-2-ethylhexanoate is then metered in over the course of 0.1 hour. After this feed has ended, polymerization is continued for 1.5 hours. Then 15.5 g of dimethylethanolamine and 1630 g of demineralized water are added. A stable dispersion with an acid number of 19 and a solids content of 22% is obtained (30 minutes at 180 ° C.).

Polyurethane dispersion 1:

614.9 g of tetramethylxylylene diisocyanate are placed in a 4 liter reaction vessel with a reflux condenser and 94 g of methyl ethyl ketoxime are metered in with stirring in half an hour. After a further hour of reaction time at 70 ° C., 180 g of polyester 1, 120.6 g of dimethylolpropionic acid, 15.7 g of trimethylolpropane monoallyl ether, 112.5 g of di-trimethylolpropane, 0.9 g of dibutyltin dilaurate and 612 g of methyl ethyl ketone are weighed into the reaction vessel. The process is continued at 85 ° C. until the isocyanate content is 0.25%. 8.5 g of methyl ethyl ketoxime are then added and the mixture is run at 85 ° C. to an isocyanate content of <0.02%. A mixture of 31.1 g of dimethylethanolamine and 1400 g of deionized water is then added. After vacuum distillation, in which the methyl ethyl ketone is removed, a dispersion with a solids content of 42% is obtained (60 minutes at 120 ° C.).

Polyurethane dispersion 2:

273.6 g of tetramethylxylylene diisocyanate are placed in a 2 liter reaction vessel with a reflux condenser, and 48.7 g of methyl ethyl ketoxime are metered in with stirring in half an hour. After a further hour of reaction time at 70 ° C., 216.3 g of polyester 5, 44.8 g of dimethylolpropionic acid, 60 g of di-trimethylolpropane, 0.3 g of dibutyltin dilaurate and 187.3 g of methyl ethyl ketone are weighed into the reaction vessel. The process is continued at 85 ° C. until the isocyanate content is 0.45%. Then 7.6 g of methyl ethyl ketoxime are added and the mixture is run at 85 ° C. to an isocyanate content of <0.02%. A mixture of 20.5 g of dimethylethanolamine and 919 g of deionized water is then added. A dispersion with a solids content of 34% (60 minutes at 120 ° C).

Polyurethane dispersion 3:

300 g of polyester 3, 60.3 g of dimethylolpropionic acid, 37.5 g of di-trimethylolpropane, 293.3 g of tetramethylxylylenediisocyanate, 0.5 g of dibutyltin dilaurate and 400 g of methyl ethyl ketone are weighed out and at 80 ° C. in a 4 liter reaction vessel with a reflux condenser heated. This mixture is kept at 80 ° C. until the isocyanate content is 2.01%. A mixture of 31.9 g of dimethylethanolamine, 90.9 g of adipic acid bishydrazide and 1489 g of completely deionized water is then added. A dispersion is obtained with a solids content of 29% (60 minutes at 120 ° C).

Polyurethane dispersion 4 (for application example):

249.4 g of polyester 3, 15.9 g of dimethylolpropionic acid, 86.9 tetramethylxylylene diisocyanate, 0.2 g of dibutyltin dilaurate and 117.2 g of methyl ethyl ketone are weighed out and heated to 85 ° C. in a 4 l reaction vessel with a reflux condenser. This mixture is kept at 85 ° C. until the isocyanate content is 1.95%. Then 76.8 g of a di-trimethylolpropane monolauric acid ester are added and the mixture is run at 85 ° C. to an isocyanate content of <0.02%. A mixture of 10.7 g of dimethylethanolamine and 1080 g of fully deionized water is then added. After vacuum distillation, in which the methyl ethyl ketone is removed, a dispersion with a solids content of 29% is obtained (60 minutes at 120 ° C.).

Preparation of the microgel dispersions according to the invention

Microgel dispersion 1:

504 g of fully demineralized water are weighed into a 2 l reaction vessel with a reflux condenser and heated to 98.degree. 10 percent by weight of a mixture of 361.2 g of polyurethane dispersion 1, 2.2 g of dimethylethanolamine, 195 g of fully demineralized water, 17.6 g of butanediol monoacyrlate, 54.8 g of styrene, 80.1 g of butyl methacrylate and 4.9 g of tert-butyl per -2-ethylhexanoate are added with stirring and mixed at 98 ° C for 15 minutes. The remaining 90 percent by weight of this mixture is then metered in uniformly within 3 hours. After the end of the feed of the mixture, a sample of the entire reaction mixture diluted with THF shows turbidity. After the end of the feed, polymerization is continued for 0.5 hours. A mixture of 3 g of methyl ethyl ketone and 0.7 g of tert-butyl per-2-ethylhexanoate is then metered in over the course of 0.1 hour. After this feed has ended, the batch is kept at 98 ° C. for a further 8 hours and then cooled. A stable dispersion with a solids content of 25% (60 minutes at 120 ° C.) is obtained. A sample of this dispersion diluted with tetrahydrofuran shows a strong turbidity. Microgel dispersion 2:

510 g of fully demineralized water, 4.8 g of dimethylethanolamine and 65.5 g of polyester 2 are weighed into a 2 l reaction vessel with a reflux condenser and heated to 96.degree. 10 weight percent of a mixture of 495.2 of the polyurethane dispersion 1, 2.2 g of dimethylethanolamine, 397 g of deionized water, 16 g Butandiolmonoacyrlat, 49.8 g styrene, 72.6 g butyl methacrylate and 2 g of ^2,2'-azo-bis g -isobutyronitrile (AIBN) are added with stirring and mixed at 96 ° C for 15 minutes. The remaining 90 percent by weight of this mixture is then metered in uniformly over the course of 2.5 hours. After the end of the feed of the mixture, a sample of the entire reaction mixture diluted with THF shows turbidity. After the end of the feed, polymerization is continued for 0.5 hours. A mixture of 3 g of methyl ethyl ketone and 0.4 g of 2,2'-azo-bis-isobutyronitrile (AIBN) is then metered in over the course of 0.1 hour. After this feed has ended, the batch is kept at 98 ° C. for a further 8 hours and then cooled. A stable dispersion with a solids content of 25% (60 minutes at 120 ° C.) is obtained. A sample of this dispersion diluted with tetrahydrofuran shows a strong turbidity.

Microgel dispersion 3:

268.4 g of tetramethylxylylene diisocyanate are placed in a 2 liter reaction vessel with a reflux condenser, and 34.8 g of methyl ethyl ketoxime are metered in with stirring in half an hour. After a further hour of reaction time at 70 ° C., 211.9 g of polyester 4, 26.8 g of dimethylolpropionic acid, 50 g of di-trimethylolpropane, 0.5 g of dibutyltin dilaurate and 274 g of methyl ethyl ketone are weighed into the reaction vessel. The process is continued at 80 ° C. until the isocyanate content is 1.80%. A mixture of 10.7 g of dimethylethanolamine, 23.7 g of hydrazine hydrate (80% in water) and 500 g of fully deionized water is then added. A sample of this dispersion diluted with tetrahydrofuran shows no visually perceptible turbidity at this time. When heating to 98 ° C, the methyl ethyl ketone is removed by distillation using a water separator. After a further reaction time of 2 hours at 98 ° C. and subsequent cooling, 7.2 g of dimethylethanolamine are added. A dispersion with a solids content of 34% is obtained (60 minutes at 120 ° C.). A sample of this dispersion diluted with tetrahydrofuran shows a strong turbidity.

Microgel dispersion 4: 500 g of polyurethane dispersion 2 and 950 g of polyurethane dispersion 3 are weighed into a 2 l reaction vessel with a reflux condenser. A sample of this mixture diluted with tetrahydrofuran shows no visually perceptible turbidity at this time. The mixture is then heated to 98 ° C. During the heating, the methyl ethyl ketone is removed by distillation using a water separator. After 1.5 hours at 98 ° C, a mixture of 8 g of dimethylethanolamine and 410 g of deionized water is added. After a further 4 hours at 98 ° C., the mixture is cooled. A dispersion with a solids content of 28% is obtained (60 minutes at 120 ° C.). A

Sample of this dispersion diluted with tetrahydrofuran shows a strong turbidity.

Use of the microgel dispersions according to the invention

Application Example 1 To prepare a metallic aqueous basecoat 93.1 g of the polyurethane dispersion 4, 216 g of the microgel according to the invention 1, 165.5 g Acrylatdisper- version 1, 19.4 g of a commercial melamine resin (Cymel ^® 327 from Dyno Cytec) , 42.9 g of a commercial aluminum bronze, pasted beforehand in 56.2 g of butyl glycol and 31, 6 g of n-butanol and a mixture of 19.8 g of a commercial acrylate thickener (Latekoll D ^® from BASF) and 50 g of demineralized water to processed a varnish. The pH is adjusted to 8.00 to 8.30 with dimethylethanolamine and to a viscosity of 100 mPas with deionized water (measured at 1000 s- ¹ ).

Example of use 2:

The procedure is as in Example 1. However, the 216 g microgel dispersion 1 are replaced by 216 g of the microgel dispersion 2 according to the invention.

Application example 3: The procedure is as in example 1. However, the 216 g microgel dispersion 1 are replaced by 158.8 g of the microgel dispersion 3 according to the invention.

Example of use 4:

The procedure is as in Example 1. However, the 216 g microgel dispersion 1 are replaced by 192.9 g of the microgel dispersion 4 according to the invention.

Comparative Example 1:

The procedure is as in Example 1. However, the 216 g microgel dispersion 1 is replaced by 216 g of a microgel dispersion produced from Example 9 from DE 39 40 316. Testing the steam jet test:

The aqueous basecoats prepared according to the application examples described above are applied by spray application in each case on a 5 × 10 cm coated polycarbonate substrate in an air-conditioned spray booth in such a way that a dry layer thickness of 15-18 μm is obtained. After an intermediate drying period of 10 minutes at 80 ° C, the substrates coated in this way are each provided with a 2K clearcoat for plastic coating, which is commercially available in the automotive industry, with a dry layer thickness of 40 - 45 μm and the layers are then baked at 80 ° C for 45 minutes. A St. Andrew's cross with a cutting length of 10 cm is incised on each of these coated test specimens using a Sikkens incisor, Erichsen type 463, 1 mm blade with a cutting angle of approx. 30 °.

The respective test specimen and the steam jet lance are fixed in such a way that the jet center is located above the St. Andrew's cross, the steam jet is parallel on a scratch, the distance from the steam jet lance to the sample body is 10 cm and the angle of incidence is 90 °.

With 60 ° C hot water, the test specimen is irradiated for 60 seconds with a trapezoidal beam pattern at a volume flow of 11-11.5 l / min. The evaluation is carried out via a visual assessment: no flaking or up to max. 1 mm infiltration is OK

Infiltration from> 1 mm to large-scale spalling is not ok.

The individual results are shown in the table below:

Table I

Table I clearly shows that the use of the microgel dispersions according to the invention gives coatings which are distinguished by good adhesion to polycarbonate. Furthermore, the examples according to the invention show very good aluminum orientation and stability as well as an excellent topcoat level.

Claims

Patent claims

1.) Emulsifier-free microgel dispersion, obtainable by intermolecular or intramolecular crosslinking in an aqueous medium of a prepolymer, the prepolymer

• at least two blocked NCO groups;

2.) Emulsifier-free microgel dispersion, obtainable by intermolecular or intramolecular crosslinking in an aqueous medium of a prepolymer, the prepolymer

• at least three blocked NCO groups;

• at least two groups with at least one active hydrogen atom bonded to a nitrogen atom;

3.) Microgel dispersion according to claim 1 or 2, characterized in that more than 70% of the groups are reacted with at least one active hydrogen atom bound to a nitrogen atom to form polyurea bonds.

4.) Microgel dispersion according to one of the preceding claims, characterized in that the group having at least one active hydrogen atom bonded to a nitrogen atom is an NH ₂ group.

5.) Microgel dispersion according to one of the preceding claims, characterized in that the prepolymer

• a number average molecular weight of more than 2,000;

• an acid number between 10 and 30 mg KOH / g;

• has at least one segment derived from a diisocyanate as the hard segment.

6.) Microgel dispersion according to one of the preceding claims, characterized in that the triol has 3 to 24 carbon atoms and is preferably trimethylolpropane.

7.) Microgel dispersion according to one of the preceding claims, characterized in that the polyol has 3 to 12 carbon atoms and is preferably di-trimethylolpropane.

8.) Microgel dispersion according to one of the preceding claims, characterized in that the linear and / or branched polyester polyol is obtainable from the polycondensation of a polycarboxylic acid with at least one diol or polyol.

9.) Microgel dispersion according to claim 8, characterized in that the linear or branched polyester polyol has a number average molecular weight between 300 and 4,000 and a hydroxyl number between 28 and 580.

10.) Microgel dispersion according to one of the preceding claims, characterized in that the blocked NCO groups are the same or different and from the reaction of a diisocyanate such as 1,1-methylenebis (4-isocyanatocyclohexane) (4,4'-dicyclohexylmethane diisocyanate, Desmodur W ), Hexamethylene diisocyanate (HMDI, 1, 6-diisocyanatohexane, Desmodur H), isophorone diisocyanate (IPDI, 3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane), 1, 4-cyclohexyl diisocyanate

(CHDI, trans, -trans-1, 4-diisocyanatocyclohexane), in particular 1, 3-bis (1-isocyanato-1-methylethyl) benzene (TMXDI, m-tetramethylxylylene diisocyanate), with a capping agent, in particular with methyl ethyl ketoxime.

11.) Microgel dispersion according to one of the preceding claims, characterized in that the group capable of forming anions comes from dimethylolpropionic acid, 9,10-dihydroxystearic acid and / or from a polyester polyol with at least one group capable of forming anions.

12.) Microgel dispersion according to one of the preceding claims, characterized in that the number average molecular weight of the prepolymer is at most 10,000, preferably between 3,000 and 7,000.

13.) Microgel dispersion according to one of the preceding claims, characterized in that the crosslinking is carried out in the presence of an additional polymer with an OH number between 30 and 400 and an acid number between 1 and 150, selected from the group of polyacrylates, polyesters and polyurethanes ,

14.) Microgel dispersion according to one of the preceding claims, characterized in that the crosslinking is carried out together with an emulsion polymerization, using

15.) Microgel dispersion according to one of the preceding claims, characterized in that the reaction mixture originating from the crosslinking is then subjected to an emulsion polymerization of at least one monomer compound which contains at least one free-radically polymerizable double bond and in particular has at least one hydroxyl group.

16.) Microgel dispersion according to claim 14 or 15, characterized in that the emulsion polymerization is carried out in the presence of at least one monomer compound without hydroxyl groups which contains at least one free-radically polymerizable double bond.

17.) Emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A dispersed in an aqueous medium and a polymer B, where

Polymer A has at least two blocked NCO groups;

• the polymer B has at least three groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer A and / or the polymer B

• at least one group capable of forming anions and wherein during the crosslinking the nitrogen atoms carrying at least one active hydrogen atom react with the blocked NCO groups to form urea bonds and to release the blocking agent.

18.) Emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A dispersed in an aqueous medium and a polymer B, where

Polymer A has at least three blocked NCO groups;

• the polymer B has at least two groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer A and / or the polymer B

19.) Emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A dispersed in an aqueous medium with a polyamine, where

Polymer A has at least two blocked NCO groups;

20.) Emulsifier-free microgel dispersion, obtainable by crosslinking a polymer A dispersed in an aqueous medium with a polyamine, where

Polymer A has at least three blocked NCO groups;

• the polyamine has at least two groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer

21.) Microgel dispersion according to one of claims 17 to 20, characterized in that the number average molecular weight of polymer A and / or polymer B is at most 10,000, preferably between 2,000 and 8,000.

22.) Microgel dispersion according to one of claims 17 to 21, characterized in that the polymer A additionally contains two uncapped NCO groups and that the polymer A chain-lengthens with a diamine and / or polyamine before crosslinking with the polymer B or polyamine becomes.

23.) Microgel dispersion according to claim 22, characterized in that the diamine or polyamine has at least one group capable of forming anions.

24.) Microgel dispersion according to claim 23, characterized in that the group capable of forming anions originates exclusively from the diamine or polyamine.

25.) Microgel dispersion according to claim 24, characterized in that the group capable of forming anions is a sulfonic acid group.

26.) Emulsifier-free microgel dispersion according to claim 25, characterized in that at least one group capable of forming anions is present per 8,000 number-average molecular weight units.

27.) Emulsifier-free microgel dispersion, obtainable by crosslinking a polymer B dispersed in an aqueous medium with a capped polyisocyanate, where

• the blocked isocyanate is not dispersible in water and has at least two blocked NCO groups;

• the polymer B has at least three groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer B

28.) Emulsifier-free microgel dispersion, obtainable by crosslinking a polymer B dispersed in an aqueous medium with a capped polyisocyanate, where

• the polymer B has at least two groups with at least one active hydrogen atom bonded to a nitrogen atom, and wherein the polymer B

29.) Microgel dispersion according to one of claims 17 to 28, characterized in that the crosslinking is carried out in the presence of an additional polymer C with an OH number between 30 and 400 and an acid number between 1 and 150, selected from the group of polyacrylates, Polyester and polyurethane.

30.) Microgel dispersion according to one of claims 17 to 29, characterized in that the crosslinking is carried out together with an emulsion polymerization of at least one hydroxyl-containing monomer compound which contains at least one free-radically polymerizable double bond.

31.) Microgel dispersion according to one of claims 17 to 30, characterized in that the reaction mixture originating from the crosslinking is subsequently subjected to an emulsion polymerization of at least one monomer compound which contains at least one free-radically polymerizable double bond and in particular has at least one hydroxyl group.

32.) Microgel dispersion according to claim 30 or 31, characterized in that the emulsion polymerization is carried out in the presence of at least one monomer compound without hydroxyl groups which contains at least one free-radically polymerizable double bond.

33.) Microgel dispersion according to one of claims 17 to 32, characterized in that the polymer A and / or B. • a number average molecular weight of more than 800;

• an acid number between 10 and 70 mg KOH / g; having.

34.) Microgel dispersion according to one of claims 17 to 33, characterized in that the diol or polyol has 2 to 36 carbon atoms and is preferably selected from the group of trimethylolpropane monoallyl ether, di-trimethylolpropane and hydroxylated fatty acid compounds.

35.) Microgel dispersion according to one of claims 17 to 34, characterized in that the polyester polyol has a number average molecular weight between 200 and 6,000, an OH number between 20 and 550 and an acid number less than 5.

36.) Microgel dispersion according to one of claims 17 to 35, characterized in that the group capable of forming anions originates from dimethylolpropionic acid and / or 9, 10-dihydroxystearic acid.

37.) Microgel dispersion according to one of claims 17 to 35, characterized in that the group capable of forming anions comes from a polyester polyol, which on average has at least one free carboxyl group per molecule, which comes from trimellitic acid, trimellitic anhydride, dimethylolpropionic acid or dihydroxystearic acid.

38.) Microgel dispersion according to one of claims 17 to 37, characterized in that at least one of the groups of the polymer having at least one active hydrogen atom bonded to a nitrogen atom from a di- or polyamine, in particular from 2-methyldiaminopentane, ethylenediamine, N , N-diethylene triamine, adipic acid bishydrazide or hydrazine segment.

39.) Microgel dispersion according to one of claims 17 to 38, characterized in that the blocked NCO groups are the same or different and from the reaction of a diisocyanate such as TMXDI (m-tetramethylxylylene diisocyanate), 1, 1-methyl-enbis (4-isocyanatocyclohexane ), (4,4'-dicyclohexylmethane diisocyanate, Desmodur W), hexamethylene diisocyanate (HMDI, 1, 6-diisocyanatohexane, Desmodur H), isophorone di-isocyanate (IPDI, 3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane) , 1,4-cyclohexyl diisocyanate (CHDI, trans, -trans-1,4-diisocyanatocyclohexane) and / or from aliphatic triisocyanates such as N-isocyanatohexylaminocarbonyl-N, N'-bis (isocyanate hexyl) urea (Desmodur N), 2, 4,6-Trioxo-1,3,5-tris (6-isocyanatohexy |) hexahydro-1,3,5-triazine (Desmodur N3300), 2,4,6-trioxo-1,3,5-tris (5-isocyanato-1, 3,3-tri- methylcyclohexylmethyl) hexahydro-1,3,5-triazine (Desmodur Z4370) with a capping agent, especially with methyl ethyl ketoxime.

40.) Emulsifier-free and acrylate-modified microgel dispersion, obtainable by emulsion polymerization of at least one hydroxyl-containing monomer compound (A) which contains at least one free-radically polymerizable double bond, in the presence of an aqueous dispersion of a polymer (B) containing the latter

• at least two blocked NCO groups;

• in the backbone of the prepolymer at least one segment originating from a diol, polyol, polyether and / or polyester polyol; and

• at least one group capable of forming anions, the hydroxyl groups of the monomer compound (A) reacting with the blocked NCO groups of the polymer (B) during the emulsion polymerization to form urethane bonds and to release the blocking agent.

41.) Microgel dispersion according to claim 40, characterized in that the emulsion polymerization is additionally carried out in the presence of at least one hydroxyl group-free monomer compound (C) which contains at least one free-radically polymerizable double bond.

42.) Microgel dispersion according to claim 40 or 41, characterized in that the emulsion polymerization is carried out in the presence of an additional polymer (D) with an OH number between 30 and 400 and an acid number between 1 and 150, selected from the group of polyacrylates, Polyester and polyurethane.

43.) Microgel dispersion according to one of claims 40 to 42, characterized in that the reaction mixture originating from the emulsion polymerization is subsequently subjected to a further emulsion polymerization with at least one monomer compound which contains at least one free-radically polymerizable double bond and in particular has at least one hydroxyl group.

44.) Microgel dispersion according to one of claims 40 to 43, characterized in that the further emulsion polymerization is carried out in the presence of at least one monomer compound without hydroxyl groups which contains at least one free-radically polymerizable double bond.

45.) Microgel dispersion according to one of claims 40 to 44, characterized in that the polymer (B)

• a number average molecular weight of more than 800; • an acid number between 20 and 150 mg KOH / g; having.

46.) Microgel dispersion according to one of claims 40 to 45, characterized in that the diol or polyol has 2 to 36 carbon atoms and is preferably selected from the group of trimethylolpropane monoallyl ether, di-trimethylolpropane and hydroxylated fatty acid compounds.

47.) Microgel dispersion according to one of claims 40 to 46, characterized in that the polyester polyol has a number average molecular weight between 200 and 6,000, an OH number between 20 and 550 and an acid number less than 5.

48.) Microgel dispersion according to one of claims 40 to 47, characterized in that the group capable of forming anions originates from dimethylolpropionic acid and / or 9,10-dihydroxystearic acid.

49.) Microgel dispersion according to one of claims 40 to 48, characterized in that the group capable of forming anions originates from a polyester polyol, which on average has at least one free carboxyl group per molecule which comes from trimellitic acid, trimellitic anhydride, dimethylolpropionic acid or dihydroxystearic acid.

50.) Microgel dispersion according to one of claims 40 to 49, characterized in that the blocked NCO groups are the same or different and from the reaction of a diisocyanate such as TMXDI (m-tetramethylxylylene diisocyanate), 1,1-methylenebis (4-isocyanatocyclohexane), (4,4'-dicyclohexylmethane diisocyanate, Desmodur W), hexamethylene diisocyanate (HMDI, 1, 6-diisocyanatohexane, Desmodur H), isophore diisocyanate (IPDI, 3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane) , 1,4-cyclohexyl diisocyanate (CHDI, trans, -trans-1,4-diisocyanatocyclohexane) and / - or from aliphatic triisocyanates such as N-isocyanatohexylaminocarbonyl-N, N'-bis (isocyanatohexyl) urea (Desmodur N), 2, 4,6-trioxo-1,3,5-tris (6-isocyanatohexyl) hexahydro-1,3,5-triazine (Desmodur N3300), 2,4,6-trioxo-1,3,5-tris (5th -isocyanato-1, 3,3-trimethylcyclohexylmethyl) hexahydro-1,3,5-triazine (Desmodur Z4370) with a capping agent, in particular with methyl ethyl ketoxime.

51.) Microgel dispersion according to one of claims 40 to 50, characterized in that the number average molecular weight of the polymer (B) is at most 10,000, preferably between 1,000 and 8,000.

52.) Microgel dispersion according to one of the preceding claims, characterized in that the microgel has an acid number between 10 and 50 mg KOH / g, in particular between 10 and 30 mg KOH / g.

53.) Use of a microgel dispersion according to one of the preceding claims for producing a multi-layer coating, in particular in the automotive industry.

54.) Use according to claim 53 for the production of a basecoat.

55.) Use according to claim 53 or 54, characterized in that the proportion of microgel, based on the solid of the layer obtainable therefrom, is between 20 and 85%, preferably between 20 and 65%.