DE10247845A1 - Emulsifier-free, acrylate modified microgel dispersion obtainable by emulsion polymerization useful in the preparation of multilayer coatings, especially in the automobile industry, and for the preparation of base paint - Google Patents

Abstract

Emulsifier-free, acrylate modified microgel dispersion obtainable by emulsion polymerization of a monomer (A) containing a radically polymerisable double bond, in the presence of an aqueous dispersion of a polymer (B) containing capped NCO groups and an anion forming group, where during emulsion polymerization the OH groups of monomer A react with the capped NCO groups of polymer B with formation of urethane compounds and release of the blocking agent is new. An emulsifier-free, acarylate modified microgel dispersion obtainable by emulsion polymerization of at least one OH group containing monomer (A) which contains at least one radically polymerisable double bond, in the presence of an aqueous dispersion of a polymer (B) containing at least two capped NCO groups, in the prepolymer backbone at least one segment derived from a diol, polyol, polyether, and/or polyesterpolyol, and at least one forming group, where during emulsion polymerization the OH groups of monomer A react with the capped NCO groups of polymer B with formation of urethane compounds and release of the blocking agent.

Description

The present invention relates to a microgel and its use in a multi-layer coating, especially in the series painting of car bodies.

For The series painting of car bodies is generally a multi-layer coating of a total of four different from each other Layers (four-layer structure) used, these four layers are applied one after the other in separate painting systems:

The first, right on the car sheet layer is an electrophonetically applied layer (Electrocoat layer, KTL layer) by electro-dip painting - mainly cathodic dip painting (KTL) - for the purpose Corrosion protection is applied and then baked.

The second, on the electrocoat layer located and about 30 to 40 microns thick layer is a so-called filler layer, on the one hand Offers protection against mechanical attacks (stone chip protection function), on the other hand ensures an adequate level of topcoat, i.e. the rough surface the body shell for the subsequent top coat smoothes and fills out minor bumps. The one for making this filler layer The paints used also contain pigments in addition to binders. there the wettability of the pigments used has an impact the top coat level of the entire multi-layer coating and also on the Gloss of the filler layer, as required by some car manufacturers. The filler layer for the most part through application with electrostatic high rotation bells and followed by Burn-in process generated at temperatures above 130 ° C.

The third, on the filler layer layer is the basecoat layer, which is covered by appropriate pigments the desired body Color there. The basecoat is applied by conventional spraying. The layer thickness of this conventional Depending on the color, the basecoat layer is between about 12 and 25 μm. Mostly this layer, especially with metallic effect paints, is divided into two Process steps applied. In a first step the application by means of electrostatic high-speed rotary bells, followed by a second order using pneumatic atomization. This Layer (using aqueous basecoat) with infrared emitters and / or intermediate dried by hot air convection.

The fourth and top one, on the basecoat layer layer is the clear lacquer layer, which is usually in one Order is applied by electrostatic high-speed rotary bells. It gives the body the desired shine and protects it Basecoat against environmental influences (UV radiation, salt water, etc.).

Then the basecoat and baked the clear coat together.

To someone in this multi-layer finish usable water-dilutable Basecoat or a basecoat layer produced therefrom in addition to the coloring property, there are other essential requirements posed:

First, the basecoat layer in hardened Condition for an optimal alignment of the used as effect pigments Lead aluminum flakes. This property known under the term "flip / flop effect" is for any metallic finish is vital. A special one good "flip / flop effect" is then achieved, if the platelet-shaped effect pigments preferably evenly in one are aligned at a flat angle to the lacquer layer.

In addition, the basecoat layer a precisely defined liability for the paint layers below and above it exhibit. The basecoat thus has the decisive influence the stone chip resistance 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 "knockout criterion", i.e. only those Multi-layer painting can be used in production allowed to, who have previously passed the VDA stone chip test. This test is passed when the finished multi-layer coating at a has precisely defined mechanical stress flaking, which is a certain area do not exceed and the separation of the basecoat from the one below located filler layer are due. Consequently, the adhesion of the basecoat film must be adjusted on the one hand, that it is high enough for the clear lacquer layer does not detach from her still so low is the filler layer in the event of stone chips not to get carried away which otherwise leads to considerable corrosion damage to the automobile body to lead would.

On the other hand, the basecoat must be one have good processability. That means that if possible in such a layer thickness can be achieved with a spray application, that sufficient color coverage is ensured. Become strong for that opaque color black only 17 μm thickness of the basecoat layer for a sufficient Color coverage required, so it is for the less opaque color white at least 45 μm. Such Applying the layer thickness with a spraying process is still possible a significant problem because the rheological properties of the water-dilutable Basecoats must be available accordingly.

For basecoats with metallic effect pigments is the problem described above, i.e. at a usual Layer thickness of approximately 18 μm to ensure adequate stability, particularly clearly. On silver metallic is a particularly critical color in this context.

The term "rheological properties" means that the varnish on the one hand during the spraying process, i.e. at high shear speeds, such a low viscosity has that it atomizes easily and on the other hand when it hits the substrate, at low shear rates, has such a high viscosity that he enough is stable and no runner formation shows. The higher the thickness of the layer is supposed to be, the bigger the problem is this contradictory Unite properties. Also the formation of a pronounced metallic effect depends on these properties together.

This basic problem is well also the reason why a large number of publications deal with specially matched binder systems or with special ones Additives for dilutable Basecoats busy.

Special additives are described to improve the rheological 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 resistance to condensation in the overall structure of an automobile coating.

Therefore, it is a desire of the paint manufacturers such additives if possible to avoid and to use such polymers as binders that the desired Bring properties on their own, so-called "tailor-made" polymers.

One of the main representatives of this Species are in water Cross-linked polymer microparticles present or dispersion called "microgels" for short.

The addition of microgels does the trick not just an improvement in the rheological properties, but also has a significant impact on the stability of the applied lacquers, the orientation of the effect pigments and the Adhesion of the basecoat to the filler layer underneath and thus a decisive influence on the stone chip resistance of multi-layer painting. However, it should be noted that the addition of microgels does not include all of the aforementioned properties be positively influenced:

Special microgels are from the EP 0 030 439 B1 and the EP 0 242 235 A1 known. 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 “core / shell” - or also referred to as “core / shell”.

The term “core / shell structure” means that the polymer particle is essentially two different Areas is built up: the inner area (core) is surrounded by an outer area (shell) surrounded, these areas have a different chemical composition have and as a result also different physical Characteristics.

The core of this microgel can be obtained from a mixture which, in addition to monofunctional monomers, also contains difunctional monomers. Crosslinking takes place using an emulsifier. Then this cross-linked microparticle according to the EP 0 030 439 B1 covered with a layer of non-crosslinked acrylic polymer and grafted. According to the EP 0 242 235 A1 the crosslinked microparticle is coated with a layer of polymerizable aromatic compounds.

Furthermore, in the EP 0 030 439 B1 described to convert the microgels present in aqueous dispersion into a non-aqueous phase and to use them for solvent-containing coating compositions.

From the EP 0 038 127 B1 . EP 0 029 637 A1 and the GB 2 159 161 A microgels are known which can be obtained by polymerizing suitable monomers in the presence of an emulsifier, for example N, N-bis (hydroxyethyl) taurine.

Such compounds are referred to under the term “emulsifier” to understand that both a hydrophilic and a hydrophobic Have rest. Emulsifiers stabilize emulsions, i.e. of disperse systems of two not or only partially with each other miscible liquids or phases, one of which is finely divided into the other. A further definition of such connections is e.g. in “Römpps Chemie Lexicon "(Vol. 2, B. edition, 1981, pp. 1126-1127). Generally one differentiates between ionic, nonionic and amphoteric emulsifiers. For coloring Coating compositions are used emulsifiers that a group derived from sulfonic acid as the hydrophilic residue and as hydrophobic residue a longer chain Fettsäurealkylrest exhibit.

A major disadvantage of the below Microgels produced using an emulsifier consist in the Remaining of the emulsifier in the finished microgel, since the latter, for example due to the sulfur-containing groups present in the emulsifier (Sulfonic acid groups), so for a variety of applications used only with significant disadvantages can be. So have such microgels because of the contained in them Emulsifier disadvantageous properties, for example with regard to on their use in waterborne basecoats in the Automotive industry, especially with regard to water storage and condensation resistance.

Also the EP 0 502 934 describes a microgel dispersion. This serves both to improve the rheological properties as well as 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.

The use of this microgel in But has basecoats in the painting of automobile bodies the disadvantage that the adhesion between the basecoat and one on it, from a powder clearcoat or a powder clearcoat slurry applied clear coat not that of the automotive industry meets the prescribed requirements.

Furthermore, from the DE 195 04 015 A1 Microgels are known which are produced 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.

These microgels have the disadvantage that the rheological properties of these varnishes no longer match meet increased requirements of the automotive industry. This is particularly evident in terms of requirements the viscosity on the one hand and 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 (in Dependent on the respective color, also lower or higher) can be achieved without running.

Furthermore, WO 00/63265 and WO 00/63266 known microgels, which consist of a multi-stage Polymerization process available are, 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 performed becomes. As a last step, the product thus obtained is treated with a Crosslinker implemented so that a fully crosslinked microgel is obtained becomes. This completely crosslinked microgel is then added to binder formulations, which contain a crosslinkable binder. During training of the finished paint film, for example under baking conditions, the binder is then crosslinked - that of the binder formulation Microgel added can be due to the lack of functionalities on this Do not participate in networking.

A problem with using this later cross-linked microgels is that waterborne basecoats that this Microgels do not contain sufficient on plastic substrates Show adhesion to directly on without an intermediate or adhesive base layer a plastic surface, for example on bumpers from Automobiles to be painted.

Object of the present invention is the provision of a water-dilutable microgel that is used in water-dilutable Basecoats, especially for the automotive industry. The available from it Multi-layer coatings are said to have the disadvantages described above overcome the state of the art, in particular, the coloring layer should have adequate adhesion on plastic substrates and the overall property level The finished multi-layer coating should meet the high requirements the automobile manufacturer (especially with regard to appearance and stone chip resistance) are sufficient.

In addition, this microgel is said to in particular with binder systems based on polyurethanes and / or polyacrylates are well compatible and particularly high quality Coatings result.

• – mindestens zwei verkappte NCO-Gruppen;
• – im Backbone des Präpolymers mindestens ein aus einem Diol, Polyol, Polyether und/oder Polyesterpolyol stammendes Segment; und
• – mindestens eine zur Anionenbildung befähigte Gruppe,

wobei während der Emulsionspolymerisation die Hydroxylgruppen der Monomerverbindung (A) mit den verkappten NCO-Gruppen des Polymers (B) unter Bildung von Urethanbindungen und unter Freisetzung des Blockierungsmittels reagieren.This object is 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) 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,

wherein during the emulsion polymerization the hydroxyl groups of the monomer compound (A) react with the blocked NCO groups of the polymer (B) to form urethane bonds and to release the blocking agent.

In principle, this implementation two major reactions involved: first, a decapping takes place instead, i.e. the blocked NCO groups are released of the capping agent converted into free NCO groups. These free NCO groups react with the corresponding others in the reaction mixture present components containing hydroxyl groups, in particular with the hydroxyl group-containing monomer compound (A). on the other hand finds a polymerization of the hydroxyl-containing monomer compound (A) instead, i.e. a so-called polymer-analogous reaction.

The emulsifier-free and acrylate-modified microgel dispersions according to the invention are aqueous and impart 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.

Within the scope of the present invention the property "aqueous" means that the dispersions of the invention no or only minor amounts of organic solvents contain. Minor amounts are those amounts that are aqueous in nature the dispersions of the invention do not destroy.

The property "pseudoplastic" means that coating compositions, containing these emulsifier-free microgel dispersions, one at higher Shear stresses or higher velocity gradient is smaller than at low values (see Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, page 546, "Shear thinning").

This structural viscosity is independent of time. This time independence means that the course of the viscosity depending on the shear rate both with increasing shear rate and with decreasing Shear rate is identical.

This pseudoplastic behavior bears on the one hand the needs the spray application and on the other hand also the requirements with regard to Storage and settling stability Bill:

When in motion, such as when pumping around a coating composition containing the microgels according to the invention contains in the ring line of the painting system and when spraying the coating composition is in a low-viscosity state, which ensures good workability. Without shear stress however, the viscosity increases on and guaranteed in this way that the one already on the substrate surface Coating composition has a reduced tendency to run off on vertical surfaces shows ("runner formation"). In the same way leads the higher viscosity in the unmoved state, such as during storage, that a Settling of any existing solid components such as Most of the pigments is prevented or a resumption of weak during the storage period separated solid components is guaranteed.

Within the scope of the present invention means the term "physical Hardening "the hardening of a layer from a coating material by filming by solvent release from the coating material, the connection within the coating via loop formation of the polymer molecules film-forming components or the binder (for the term cf. Rompp Lexicon Varnishes and printing inks, Georg Thieme Verlag, Stuttgart, New York, 1998, "Binders", pages 73 and 74) he follows. Or the filming takes place via the coalescence of binder particles (cf.Römpp Lexicon of lacquers and printing inks, Georg Thieme Verlag, Stuttgart, New York, 1998, "Hardening", pages 274 and 275). Usually are for this no crosslinking agents necessary. If necessary, the physical hardening supported by heat or exposure to actinic radiation.

In contrast, the term "chemical hardening" means hardening a Layer of a coating material by chemical reaction (see "Hardening of Plastics "in Römpps Chemie Lexikon, B. Aufl., 1983, p. 1602 f.).

Usually becomes chemical hardening achieved by atmospheric oxygen or by crosslinking agents.

In that for the present invention polyester polyol used is a compound the available is from the polycondensation of at least one of the following described diols or polyols with at least one polycarboxylic acid or their anhydride.

Examples of suitable polycarboxylic acids are aromatic, aliphatic and cycloaliphatic polycarboxylic acids. Prefers aromatic and / or aliphatic polycarboxylic acids are used.

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

Examples of suitable acyclic, aliphatic or unsaturated polycarboxylic 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, azelaic acid, sebacic, 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, 4-methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid, tetrahydrophthalic acid or tetrahydrophthalic acid 4-methyltetrahydrophthalic. These dicarboxylic acids can both in their cis and in their trans form and as a mixture both forms can be used.

Also suitable are the transesterifiable derivatives of the abovementioned polycarboxylic acids, such as, for example, their mono- or polyvalent esters with aliphatic alcohols having 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 can also be used together with the polycarboxylic 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. Isononanoic acid is preferably used as the monocarboxylic acid.

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

1,6-Hexanediol and Neopentyl glycol is particularly advantageous and therefore special preferably 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 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 production of the polyester diols is the unsubstituted ε-caprolactone, where m has the value 4 and all R substituents are hydrogen, prefers. The reaction with lactone is characterized by low molecular weight Polyols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol or dimethylolcyclohexane started. It can however, other reaction components such as ethylenediamine, alkyldialkanolamines or also urea can be reacted with caprolactone. As a higher molecular weight Diols are also suitable polylactam diols, which are produced by the reaction of, for example, ε-caprolactone be produced 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 -) _p OH, 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.

The polyether diols are said to be on the one hand no excessive amounts bring in ether groups, because otherwise the formed to be used according to the invention Swell polyurethane in water. On the other hand, they can be used in quantities be the non-ionic stabilization of the polyurethanes guaranteed.

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

Under the designation "at least one capable of forming anions Group "become such Groups and / or segments understood in an aqueous environment by neutralizing agents be converted into anions can. By choosing the type and amount of such groups, the acid number of the polymer and above the acid number of the resulting microgel can be adjusted.

Examples of more suitable functional Groups that are converted into anions can, are carboxylic acid, sulfonic acid or phosphonic acid groups, especially carboxylic acid groups.

in der R² ein Wasserstoffatom oder eine Alkylgruppe mit bis zu 20 Kohlenstoffatomen darstellt, R³ und R⁴ unabhängig voneinander jeweils lineare oder verzweigte Alkylengruppen mit 1 bis 6 Kohlenstoffatomen, bevorzugt -CH₂-, darstellen. Beispiele für solche Verbindungen sind 2,2-Dimethylolessigsäure, 2,2-Dimethylolpropionsäure, 2,2-Dimethylolbuttersäure und 2,2-Dimethylolpentansäure. Die bevorzugten Dihydroxyalkansäuren sind 2,2-Dimethylolpropionsäure und 9,10-Dihydroxystearinsäure.In particular, the functional groups come from compounds which can be converted into anions, such as dihydroxypropionic acid, dihydroxysuccinic acid, dihydroxybenzoic acid, dihydroxy-cyclohexane monocarboxylic acid and 2,2-dialkylolalkanoic acids of the formula

in which R ^{2 represents} a hydrogen atom or an alkyl group having up to 20 carbon atoms, R ³ and R ⁴ each independently represent linear or branched alkylene groups having 1 to 6 carbon atoms, preferably -CH ₂ -. Examples of such compounds are 2,2-dimethylol acetic acid, 2,2-dimethylol propionic acid, 2,2-dimethylol butyric acid and 2,2-dimethylol pentanoic acid. The preferred dihydroxyalkanoic acids are 2,2-dimethylolpropionic acid and 9,10-dihydroxystearic acid.

Examples of suitable neutralizing agents for in Anion convertible functional groups are ammonia or amines, such as. Trimethylamine, triethylamine, tributylamine, dimethylaniline, Diethylaniline, triphenylamine, dimethylethanolamine, diethylethanolamine, Methyldiethanolamine, 2-aminomethylpropanol, dimethylisopropylamine, Dimethylisopropanolamine or triethanolamine. Is preferred as Neutralizing agent dimethylethanolamine and / or triethylamine used.

The term “neutralize” means that - based on the neutralization used onsmittel - 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:

The term "polyisocyanate" is used here and in following understood a compound, the at least two NCO groups having. Consequently, this definition also includes diisocyanates.

The mandatory for the output connection masked NCO groups can are obtained by using corresponding free NCO groups the usual, capping or blocking agents known in polyurethane chemistry implements.

In the networking according to the invention it should be noted that the capping agent is under reaction conditions is released. Likewise, the formation of cross-linked particles clearly observed.

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 for about 1 minute in an ultrasonic bath -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 according to the following formula :

Under the term "mostly be networked " understood such microgels related to the cross-linked part a proportion of uncrosslinked polymers of not more than 30% by weight exhibit.

With regard to the microgel according to the invention this means that the networked core is then referred to as "largely networked," if it contains no more than 30% by weight of uncrosslinked components.

Regarding a detailed Production of polyurethanes, their starting products and the techniques and methods for modifying them, such as chain extension, Networking, is based on 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 ed., Volume 21, pp. 665 to 716 and M.J. Husbands et al. "A Manual of Resins for Surface Coatings ", (1987) SITA Technology, London, Volume 3, pp. 1 to 59.

The particular advantage with the emulsifier-free according to the invention and acrylate-modified microgels according to the previously described embodiments is that their addition to waterborne coating compositions a clear and positive improvement of special properties causes.

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 that 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 , with addition of 20% of the emulsifier-free microgel dispersion according to the invention, based on the solids content of the coating composition, the dry film thickness being cured basecoat layer is 22 μm without runners being observed.

The emulsifier-free and acrylate-modified according to the invention Microgel is particularly suitable for manufacturing and Formulation water-dilutable Basecoats, especially for those used in the automotive industry.

In addition, the emulsifier-free according to the invention and acrylate-modified microgel dispersion of the color coating composition adequate adhesion to plastic substrates.

This characteristic is particularly noteworthy since this paint in unchanged Wording for both metallic, pre-treated substrates (automobile bodies) as also for Attachments for Automobiles made of plastic (e.g. bumpers) can be used. This avoids color deviations. So far it was for the area industrial applications often required, starting from water-dilutable Basecoats for the serial painting of car bodies, their liability for plastic substrates specifically by adding so-called "adhesion promoters" or even through additional To increase adhesive layers.

The excellent liability of the microgel according to the invention containing basecoats is shown by the for in the automotive industry as a test for sufficient liability for established "steam jet tests".

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

Furthermore, the emulsifier-free according to the invention and acrylate-modified microgel dispersions are excellent Can be used together with binder systems based on polyurethanes, polyacrylates or mixtures of polyurethanes and polyacrylates. This good usability is particularly evident in the good adhesion properties of the resulting paint film on plastic substrates. coating compositions from a combination of a binder system based on Polyurethanes and / or polyacrylates and the emulsifier-free according to the invention Microgel dispersions result in very high quality coatings.

According to a preferred embodiment In the present invention, the emulsion polymerization is additionally described in Presence of at least one hydroxyl group-free monomer compound (C) performed which contains at least one radically polymerizable double bond.

This makes the networking points scattered and subject to statistical distribution.

Monomers (C) with at least one radical polymerizable double bond that has no hydroxyl group have, for example

• - vinyl aromatic Connections such as Vinyl toluenes, 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 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, furturyl (meth) acrylate, Octyl (meth) acrylate, 3,5,5-trimetyhlhexyl (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) acrylic acid amide;
• - Acryloyloxy or methacryloyloxyethyl, propyl or butyl carbamate or allophanate; further examples of suitable monomers which contain carbamate groups are described in the patents US 3,479,328 . US 3,674,838 . US 4,126,747 . US 4,279,833 or US 4,340,497 described;
• - epoxy groups containing monomers such as the glycidyl ester of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic or allyl glycidyl ether.

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

In this embodiment of the invention the polymer containing hydroxyl groups can be linked to the microgel take part.

If this polymer (D) is water-dilutable, it becomes after solution polymerization among the measures known per se dispersed in water. Otherwise, it will not be in water dilutable Polymer (D) together with the one not yet dispersed in water Polymer (B) formed a premix, which is then a dispersion undergoes in water.

The polymer (D) can be used in an amount between 5 and 30% by weight, based on the solids content of the entire coating composition be added.

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

In addition, liability the emulsifier-free according to the invention Coating composition containing microgel dispersion increased.

Suitable polyacrylates are included available by solution polymerization of hydroxyl-containing monomers and alkyl (meth) acrylates, and optionally (meth) acrylic acid, styrene and / or ethylenic unsaturated Monomers.

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

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

Suitable hydroxyl groups Polyesters are those as described below in the Polyester polyols listed are.

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

Suitable polyurethanes are available from the implementation of at least one diol, polyol, polyether and / or a polyester polyol with at least one polyisocyanate in the sense of the present invention.

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

As a solvent for this solution polymerization solvents not containing hydroxyl groups are used, especially preferably ketones, e.g. Methyl ethyl ketone, methyl isobutyl ketone or methyl amyl ketone.

In addition, the present concerns Invention in a further, also preferred embodiment an emulsifier-free microgel dispersion in which the crosslinking originating reaction mixture then a further emulsion polymerization is subjected to at least one monomer compound, the Monomer compound contains at least one radically polymerizable double bond.

This monomer compound with at least a radically polymerizable double bond is special preferably containing hydroxyl groups.

As monomer compounds containing hydroxyl groups with at least one radically polymerizable double bond are to be mentioned:

• - hydroxyalkyl esters acrylic acid, methacrylic acid or another α, β-olefinic unsaturated Carboxylic acid, which are derived from an alkylene glycol that esterifies with the acid is, or by reacting the α, β-olefinically unsaturated carboxylic acid are available with an alkylene oxide such as ethylene oxide or propylene oxide, in particular hydroxyalkyl esters of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic, in which the hydroxyalkyl group contains up to 20 carbon atoms, such as e.g. 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-1H-indene-dimethanol or methyl propanediol monoacrylate, -onomethacrylate, -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 branched in the α-position with 5 to 18 carbon atoms per molecule, in particular a Versatic ^® acid, or instead of the reaction product, an equivalent amount of acrylic and / or methacrylic acid then during or after the polymerization reaction with the glycidyl ester of a monocarboxylic acid branched in the α-position with 5 to 18 C atoms per molecule, in particular a Versatic ^® acid, is reacted.

Such a dispersion emulsifier-free microgel is in a core / shell structure. there is the inner area according to the definition given above Mostly networked. The outer area this core / shell microgel is not networked. A networking the outer shell takes place when using a monomer compound with at least a radically polymerizable double bond only under baking conditions for the Manufacture of appropriate multi-layer coatings.

Partial crosslinking in the finished lacquer via the outer shell is only guaranteed albeit a hydroxyl group-containing monomer compound with at least a free-radically polymerizable double bond is used.

According to this embodiment the polymerized monomer mixture does not take up crosslinking to the microgel part.

In addition, one shows this Coating composition containing emulsifier-free microgel dispersion such an excellent liability that it is also considered critical Multi-layer coatings, especially in connection with powder clearcoats, can be used in automotive OEM painting.

In the case of 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. The use of a monomer compound without Hy Surprisingly, droxyl groups further reinforce this positive adhesion property.

Such a dispersion emulsifier-free microgel is in a core / shell structure. there is the inner area according to the definition given above Mostly networked. The outer area this core / shell microgel is also not networked. In contrast The core / shell polymer described above can be burned in for the Production of appropriate multi-layer coatings no crosslinking the outer shell respectively.

According to this embodiment it is ensured that the emulsion polymenisate crosslinks while who cannot participate in film education. This will make an excellent one Adhesion to plastic substrates achieved, also in connection with Powder clear coats.

higher-functional Monomers of the type described above are generally used in appropriate amounts. As part of the present Invention are under appropriate amounts of higher functional monomers to understand such quantities as for crosslinking, but not for gelation the microgel dispersion.

The orientation of the effect pigments accordingly when using emulsifier-free microgel dispersions this embodiment in watery Metallic basecoats significantly improved.

This implementation points methodologically seen no peculiarities, but takes place according to the usual and known methods of radical emulsion polymerization in the presence of at least one polymerization initiation.

Examples of suitable polymerization initiators are free radical initiators such as dialkyl peroxides, such as Di-tert-butyl peroxide or dicumyl penoxide; Hydroperoxides such as cumene hydoperoperoxide or tert-butyl hydroperoxide; Perests, such as tert-butyl perbenzoate, tert-butyl perpivalate, tert-butylpen-3,5,5-tnimethyl hexanoate or tert-butylpen-2-ethylhexanoate; Potassium, sodium or ammonium penoxodisulfate; Azodinitniles such as azobisisobutynonitrile; C-C-cleaving initiators such as benzpinacol silyl ether or a combination of a non-oxidizing initiator with hydrogen peroxide. Prefers become water-insoluble Initiators used. The initiators are preferred in one Amount from 0.1 to 25% by weight, particularly preferably from 0.75 to 10% by weight, based on the total weight of the monomers (A).

One possibility is to initiate polymerization through a redox system. This in the emulsion polymerization technique well-known method takes advantage of the fact that hydroperoxides with suitable reducing agents even at very low temperatures be encouraged to radically decay.

Suitable reducing agents are, for example Sodium metabisulfite or its formaldehyde addition product (Na hydroxymethanesulfinate). Isoascorbic acid is also very suitable. Particularly advantageous is the combination of tert-butyl hydroperoxide, (iso) ascorbic acid and Iron (II) sulfate.

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

In the solutions or the aqueous ones The corresponding monomers are then emulsions with the help of radical 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 Polymerized at 90 ° C. When working under excess pressure emulsion polymerization can also be carried out at temperatures above 100 ° C are carried out.

The same applies to solution polymerization when higher boiling organic solvents and / or overpressure is applied.

It is preferred that with the initiator feed some time, generally about 1 to 15 minutes, before the feed of the monomers is started. A method is also preferred where the initiator addition is at the same time as the addition of the monomers started and about half an hour after the addition of the monomers has ended, is ended. The initiator will preferably added in a constant amount per unit of time. To Completion of the initiator addition is the reaction mixture long (usually 1 to 1.5 hours) at the polymerization temperature held until all of the monomers used are essentially fully implemented have been. "In the essentially complete implemented " mean that preferably 100% by weight of the monomers used have been implemented, but it is also possible that a minor Residual monomer content of at most up to about 0.5% by weight, based on the weight of the reaction mixture, remain unconverted can.

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

• – ein zahlenmittleres Molekulargewicht von mehr als 800;
• – eine Säurezahl zwischen 20 und 150 mg KOH/g;

auf.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 current knowledge the number average molecular weight has a significant impact on the Rheology of the emulsifier-free according to the invention Coating composition containing microgel dispersion.

In general, a higher number average Molecular weight an increase the cross-linking points within the microgel (i.e. the mesh size of the polymer is increased).

However, it is important here that sufficient even with a high number average molecular weight stability the dispersion at one for the stabilization in water ensures a sufficient degree of neutralization.

According to a preferred embodiment The present invention is used as a diol or polyol, the corresponding Segment in the backbone of the polymer (B) is a diol and / or polyol with 2 to 36 carbon atoms.

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, Hydroxypivalinsäureneopentylester, Neopentyl glycol, diethylene glycol, 1,2-, 1,3- or 1,4-cyclohexanediol, 1,2-, 1,3- or 1,4-cyclohexanedimethanol, trimethylpentanediol, ethyl butyl propanediol, the positionally isomeric diethyloctanediols, 2-butyl-2-ethylpropanediol-1,3, 2-butyl-2-methyl propanediol-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-dihydroxymethylbi-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 (Unichema).

The following may be mentioned as polyols: trimethylolpropane, Glycerin, pentaerythritol, di-trimethylolpropane, di-pentaerythritol, as well as hydroxylated, epoxidized linseed or soybean oils.

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

Especially through the use polyols (i.e. compounds with more than three OH groups) becomes a higher one here too functionality of the prepolymer guaranteed so an increased Networking is achieved, which results in improved rheological Properties of the coating compositions containing these microgel dispersions shows.

In that for the present invention polyester polyol used is a compound the available is from the polycondensation of at least one of the previously described Diols or polyols with at least one polycarboxylic acid or their anhydride.

Examples of suitable polycarboxylic acids are aromatic, aliphatic and cycloaliphatic polycarboxylic acids. Prefers aromatic and / or aliphatic polycarboxylic acids are used.

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

Examples of suitable acyclic, aliphatic or unsaturated polycarboxylic 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, azelaic acid, sebacic acid; taking 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, 4-methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid, tetrahydrophthalic acid or tetrahydrophthalic acid 4-methyltetrahydrophthalic. These dicarboxylic acids can both in their cis and in their trans form and as a mixture both forms can be used.

The transesterifiable derivatives are also suitable the above-mentioned polycarboxylic acids, such as. their mono- or polyvalent esters with aliphatic alcohols with 1 to 4 carbon atoms or hydroxy alcohols with 1 to 4 carbon atoms. Moreover can the anhydrides of the abovementioned polycarboxylic acids can also be used, provided that they exist. If necessary, you can together with the polycarboxylic acids also monocarboxylic acids are used, 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.

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

1,6-Hexanediol and Neopentyl glycol is particularly advantageous and therefore special preferably used.

Further examples of suitable polyols are polyester diols which are obtained by reacting a lactone with egg a diol can be obtained. 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 production of the polyester diols is the unsubstituted ε-caprolactone, where m has the value 4 and all R substituents are hydrogen, prefers. The reaction with lactone is characterized by low molecular weight Polyols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol or dimethylolcyclohexane started. It can however, other reaction components such as ethylenediamine, alkyldialkanolamines or also urea can be reacted with caprolactone. As a higher molecular weight Diols are also suitable polylactam diols, which are produced by the reaction of, for example, ε-caprolactam be produced 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 -) _p OH, 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.

The polyether diols are said to be on the one hand no excessive amounts bring in ether groups, because otherwise the formed to be used according to the invention Swell polyurethane in water. On the other hand, they can be used in quantities be the non-ionic stabilization of the polyurethanes guaranteed.

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 another, also preferred embodiment In 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 regarding an advantageous - for use the emulsifier-free according to the invention Microgels in coating compositions - suitable crosslinking achieved when in the backbone of the polymer (B) from different OH functional compounds, i.e. from different diols, polyols, Polyether and / or polyester polyols, originating segments present are.

This networking also has one decisive influence both on liability and orientation the effect pigments, the stability, as well as the rheology the emulsifier-free according to the invention Coating composition containing microgel dispersion.

By choosing a suitable low molecular weight Polyols and a long chain, linear and / or branched polyester polyol a high crosslinking density is achieved, the distance between the respective network centers is sufficiently high that the rheological properties can be positively influenced.

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

These specially selected connections give the dispersion a significantly improved stability.

According to another, likewise preferred embodiment The present invention is derived from the group capable of forming anions from a polyester polyol, which on average at least one free carboxyl group per molecule which consists of trimellitic acid, trimellitic anhydride, dimethylolpropionic or dihydroxystearic acid comes.

Again, the stability of the dispersion authoritative Functionality over a additional connection introduced so that the risk of gelling during the preparation of the prepolymer reduced and at the same time increased functionality of the prepolymer building blocks is achieved.

The capped NCO groups, same or different, come from the reaction with a compound, which in turn results from the reaction of a polyisocyanate with a suitable Capping agent results. The term "blocking agent" is synonymous with the term "capping agent".

All are suitable as polyisocyanates Compounds used in the manufacture of waterborne basecoats Find use. Examples of such polyisocyanates are to call:

• - 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 will be with 1,1-methylenebis (4-isocyanatocyclohexane), (4,4'-dicyclohexylmethane diisocyanate, Desmodur W), hexamethylene diisocyanate (HMDI, 1,6-diisocyanatohexane, Desmodur N), isophorone diisocyanate (IPDI, 3,5,5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane), 1,4-cyclohexyl diisocyanate (CHDI, trans, -trans-1,4-diisocyanatocyclohexane), 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 N 3300), 2,4,6-trioxo-1,3,5-tris (5-isocyanato-1,3,3-trimethylcyclohexylmethyl) hexahydro-1,3,5-triazine (Desmodur Z4370) achieved.

That is very particularly preferred Use of TMXDI (m-tetramethylxylylene diisocyanate), which after Reaction with a capping agent the capped NCO groups brings.

Such connections are referred to as "capping agents" understood that with the NCO groups of a polyisocyanate in the React in such a way that the polyisocyanate capped in this way at room temperature Hydroxyl groups resistant is. With increased Temperatures, usually in the range of about 90 to 300 ° C, reacts the capped polyisocyanate with elimination of the capping agent.

For the capping (or blocking) of the polyisocyanates can be any suitable aliphatic, cycloaliphatic or aromatic alkyl mono alcohols be used. Examples of this are 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. It can also small proportions of higher molecular weight and relatively volatile Monoalcohols may also be used, these alcohols after they split off act as plasticizers in the coatings.

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 using the capping agent in sufficient quantity reacts with the organic polyisocyanate, so that no free Isocyanate groups are more present.

Examples of suitable blocking agents are

• a) phenols such as phenol, cresol, xylenol, nitrophenol, Chlorophenol, ethylphenol, tert-butylphenol, hydroxybenzoic acid, esters this acid or 2,5-di-tert-butyl-4-hydroxytoluene;
• b) Lactams such as "-Caprolactam," -Valerolactam, "-Butyrolactam or β-propiolactam;
• c) active methylenic compounds, such as diethyl malonate, dimethyl malonate, ethyl acetoacetate or methyl ester 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, propylene glycol monomethyl ether, methoxymethanol, Glycolic acid, Glykolsäureester, Lactic acid, Milchsäureester, Methylol urea, methylol melamine, diacetone alcohol, ethylene chlorohydrin, Ethylene bromohydrin, 1,3-dichloro-2-propanol, 1,4-cyclohexyldimethanol or acetocyanhydrin;
• 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 or butylphenylamine;
• i) imidazoles such as imidazole or 2-ethylimidazole;
• j) ureas such as urea, thiourea, ethylene urea, Ethylene thiourea or 1,3-diphenyl urea;
• k) carbamates such as phenyl N-phenylcarbamate or 2-oxazolidone;
• l) 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 oximes;
• n) salts of the 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, especially dimethylpyrazole or triazoles; such as
• q) mixtures of these blocking agents, especially dimethylpyrazole and triazoles, malonic esters and acetoacetic acid esters or dimethylpyrazole and succinimide.

Particularly preferred in the sense of The present invention is methyl ethyl ketoxime as a capping agent.

To counter the risk of gelling, can the polyisocyanates described above are partially capped.

This means the implementation of the polyisocyanate with a capping agent in deficit. hereby however, the entire polyisocyanate is not partially capped. The obtainable in this way Mixture of partially masked polyisocyanate and the rest, not then capped polyisocyanate is then with the other components implemented for emulsifier-free microgel dispersion.

In addition to the previously described embodiments the microgel can also have other structural units in its backbone or have segments that are from the usual in paint chemistry used starting components come.

For example, the polymer A contain polyurethane segments made from the previously described uncapped polyisocyanates and hydroxyl groups Compounds (e.g. diols, polyester polyols, polyethers) originate.

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 will make a optimal area for a sufficiently high degree of crosslinking with a sufficiently high level at the same time Mesh size achieved.

According to another, likewise preferred form of the invention, the microgel has an acid number between 10 and 30 mg KOH / g.

On the one hand there is sufficient stability in water and on the other hand not excessively high hydrophilicity achieved, i.e. the resulting varnishes do not show insufficient ones Condensation resistance.

The previously described emulsifier-free Microgel dispersion according to the invention is particularly suitable for production a multi-layer coating, especially in the automotive industry.

That is very particularly preferred 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 of the available from it Layer, between 20 and 85%, preferably between 20 and 65%, lies.

It is also surprising that the emulsifier-free according to the invention Micro gel dispersions in addition to the usual Layered silicates in water-dilutable Basecoats can be used. In this case, the resulting paint films do not show any insufficient resistance to condensation.

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

• 1) a first one, on the electrically conductive substrate located layer of an electrophoretically deposited coating agent;
• 2) a second, color-providing layer, obtainable from a water-dilutable Coating composition containing the emulsifier-free according to the invention Contains micro gel dispersion; and
• 3) a third layer of clear varnish.

With this multi-layer coating is in particular only three different layers to emphasize that the resulting multi-coat paint too has a sufficient stone chip resistance, which on the special properties of the emulsifier-free microgel present invention-containing water-borne basecoat.

It is also possible that the multi-coat paint consist of four different layers, i.e. out

• 1) a first one, on the electrically conductive substrate located layer of an electrophoretically deposited coating agent;
• 2) a second layer of primer or filler;
• 3) a third, color-providing layer, obtainable from a water-dilutable Coating composition containing the emulsifier-free according to the invention Contains micro gel dispersion; and
• 4) a fourth layer of a clear lacquer.

An advantage in this four-layer structure is that the cured coloring layer the stone chip protection properties of the second filler layer still positively influenced.

By using the emulsifier-free microgel according to the invention, a - based on conventional basecoats - significantly higher layer thickness can be achieved. 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.

With the coating agents to be deposited electrophoretically it is watery Coating compositions with a solids content of about 10 to 20% by weight, the usual Binder, ionic or convertible into ionic substituents and capable of chemical crosslinking Wear groups and contain pigments and other common 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 described.

The clear coat that is used in a Multi-layer paint for Automobiles over the color-imparting basecoat layer can be obtained are obtained by applying and baking a customary, solvent-based or aqueous clear lacquer composition, which is available as a one-component or two-component mixture and contains one or more base resins as film-forming binders. Provided the binders are not self-crosslinking, the clear coat composition optionally also contain crosslinkers. As a film-forming binder (Base resins) can for example polyester, polyurethane and / or poly (meth) acrylate resins used become.

In addition to the chemically crosslinking binders and, if appropriate, crosslinking agents, these clear lacquers can contain customary lacquer additives, such as. Contain catalysts, leveling agents and light stabilizers.

Examples of solvent-borne clear lacquer compositions in one-component or two-component mixtures are shown 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 described.

Examples of aqueous clear lacquer compositions in one-component or two-component mixture 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 , especially in the DE 44 19 216 A1 and DE 44 42 518 A1 , described.

The clear coat can also be made a powder clearcoat or a powder clearcoat slurry can be produced.

With regard to the powder clearcoat or the powder clearcoat slurry, the 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 , as well as on the EP 0 714 958 , referred.

But it is also possible that Microgel dispersion according to the invention in a non-aqueous Phase and in solvent-based To use coating compositions.

To microgels in non-aqueous To arrive phase, the present invention must be in an aqueous phase Microgels are removed from the water.

This can be done by any known method, for example by spray drying, Freeze-drying or evaporation, if necessary under reduced pressure Pressure, happen.

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

According to a preferred variant it becomes watery Phase present microgel converted into a liquid organic phase. This can be done by an azeotropic distillation. Here you can proceed in such a way that the watery, emulsifier-free microgel dispersion at elevated temperature, if necessary under reduced pressure, continuously or discontinuously is placed in a reactor containing 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 suitable Condensing device and a water separator with return to Reactor equipped. After reaching the boiling point of the azeotrope the gaseous increases azeotropic phase (i.e. entrainer and water) into the condenser on. 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. With a continuous azeotropic Distillation flows the entrainer back again into the reactor so that only small amounts of entrainer are used have to. The water obtained from the water separator is free of organic Ingredients and can be used again to produce the aqueous Microgel dispersion can be used.

The entrainer can be from the group of xylene, butyl acetate, methyl isobutyl ketone, methyl amyl ketone, pentanol, Hexanol or ethylhexanol selected his.

A major advantage here is that the entrainer after conversion into the organic phase stays there and for the use of solvent-based Coating compositions is advantageous. With regard to the further use of these microgels present in the organic phase for the production of solvent-based Coating compositions are the aforementioned entraining agents suitable solvents.

This procedure stands out due to the simultaneous reuse of the entrainer and the accruing Water without additional Procedural steps through an extraordinary Degree of environmental because there are no by-products to be disposed of, which in comparison incurred in large quantities with known manufacturing processes.

In a special form of azeotropic Distillation is carried out in such a way that the aqueous emulsifier-free Microgel dispersion in a mixture of an entrainer and one high-boiling organic solvents is given. This high-boiling, organic solvent prevents during the transfer into the organic phase a caking of the microgels on the wall of the Reactor.

The high-boiling solvent can be selected from the group of glycol esters, e.g. Butyl glycol acetate and / or Butyl diglycol acetate selected his.

As in the case of the entrainer the high-boiling solvent also one for a solvent-based Coating composition usual Component.

The so available Microgel can be used especially for solventborne Coating compositions are used.

A preferred form of use of the Invention is the use in solvent-based Basecoats, especially effect basecoats and clearcoats, for topcoats or painting of automobiles.

This is in an organic phase Microgel gives this solvent-based Coating compositions also have excellent application behavior. and excellent decorative properties, for example based on a pronounced Metalliceffekt, a very good resistance to runoff in the Vertical (SCA - Sagging Control Agent), freedom from clouds, resistance to re-dissolving by Clear varnish, good sanding marks coverage and compliance with usual in the automotive industry Show property specifications.

The microgels can also be good for manufacturing of solvent-based Clear lacquers, coil coating compositions and stoving lacquers for industrial use Applications as well as paints used for the construction sector become.

Another peculiarity of this Microgel lies in its high shear resistance. This attribute allows for the first time use of such microgels for the production of pigment preparations, in particular as a rubbing agent for Tinting pastes. This ensures that the tinting pastes produced in this way have a high pigment content with low viscosity.

Claims (16)

Emulsifier-free and acrylate-modified microgel dispersion, available by emulsion polymerization of at least one containing hydroxyl groups Monomer compound (A) which has at least one radical polymerizable Contains 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 derived from a diol, polyol, polyether and / or polyester polyol Segment; and - at least one capable of forming anions Group, being during the emulsion polymerization, the hydroxyl groups of the monomer compound (A) with the blocked NCO groups of the polymer (B) to form Urethane bonds react and release the blocking agent. Emulsifier-free and acrylate-modified microgel dispersion according to claim 1, characterized in that the emulsion polymerization additionally in the presence of at least one hydroxyl-free monomer compound (C) performed is the at least one radically polymerizable double bond contains. Emulsifier-free and acrylate-modified microgel dispersion according to claim 1 or 2, characterized in that the emulsion polymerization in the presence of an additional Polymers (D) with an OH number between 30 and 400 and an acid number performed between 1 and 150 will be chosen from the group of polyacrylates, polyesters and polyurethanes. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, characterized in that the reaction mixture originating from the emulsion polymerization subsequently a further emulsion polymerization with at least one monomer compound, which contains at least one radically polymerizable double bond, and in particular has at least one hydroxyl group becomes. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, 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. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, characterized in that the polymer (B) - on number average molecular weight of more than 800; - an acid number between 20 and 150 mg KOH / g; having. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, characterized in that the diol or polyol has 2 to 36 carbon atoms and preferably selected is from the group of trimethylolpropane monoallyl ether, di-trimethylolpropane and hydroxylated fatty acid compounds. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, 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 has less than 5. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, characterized in that enabled them to form anions Group from dimethylolpropionic acid and / or 9,10-dihydroxystearic comes. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, characterized in that enabled them to form anions Group comes from a polyester polyol, the statistical average has at least one free carboxyl group per molecule consisting of trimellitic acid, trimellitic anhydride, Dimethylolpropionäure or dihydroxystearic acid comes. Emulsifier-free and acrylate-modified 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 TMXDI (m-tetramethylxylylene diisocyanate), 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-cyclohexyldiiso cyanate (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 (5-isocyanato-1,3,3-trimethylcyclohexylmethyl) hexahydro-1,3,5-triazine (Desmodur Z4370) with a capping agent, in particular with methyl ethyl ketoxime, come. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, characterized in that the number average molecular weight of the polymer (B) is at most 10,000, preferably between 1,000 and 8,000. Emulsifier-free and acrylate-modified microgel dispersion according to one of the preceding claims, characterized in that the microgel has an acid number has between 10 and 30 mg KOH / g. Use of an emulsifier-free and acrylate-modified Microgel dispersion according to one of the preceding claims for Manufacture of a multi-layer coating, especially in the automotive industry. Use according to claim 14 for the production of a Basecoat. Use according to claim 14 or 15, characterized in that that the proportion of microgel, based on the solids of the available from it Layer, between 20 and 85%, preferably between 20 and 65%, lies.