WO1995019400A2

WO1995019400A2 - Additives, their production, cathodically precipitable electrophoretic enamelling baths and their use

Info

Publication number: WO1995019400A2
Application number: PCT/EP1995/000078
Authority: WO
Inventors: Klausjörg Klein; Matthias Kimpel; Bettina Vogt-Birnbrich
Original assignee: Herberts Gesellschaft mit beschränkter Haftung
Priority date: 1994-01-15
Filing date: 1995-01-11
Publication date: 1995-07-20
Also published as: DE4401045C1; WO1995019400A3

Abstract

Additives are disclosed, as well as their production and use in cathodically precipitable aqueous electrophoretic enamelling baths, in particular as anti-cratering agents causing no slippage effect, and baths containing the same. The additives are statistical polymers having the schematic formula (I): -[-(CH2CHX)a (CH2CHOR)b (CH2CHOR')c (CH=CH)d-]-n, in which a = 0 to 20 % by moles; b = 50 to 99 % by moles; c = 0 to 50 % by moles; d = 0 to 50 % by moles; n = 5 to 1500; X stands for a substituent different from OR and OR'; R stands for C1- to C10-alkyl; R' stands for H and/or -COR''; R'' stands for C1- to C3-alkyl and the sum c + d equals at least 1 % by moles.

Description

Additives, their preparation, cathodic electrodeposition baths containing them and their use.

The invention relates to the addition of additives to improve the surface in cathodic electrocoating, in particular the addition of anti-cratering agents. These are anti-cratering agents that can be produced by polymer-analogous implementation. Films are deposited from electrodeposition baths that have been improved in this way; these can be used, for example, as a primer layer in a multilayer coating.

Cathodic electrocoating (KTL) is a process that is frequently used, especially for priming automobile bodies, in which synthetic resins bearing water-dilutable cationic groups are deposited on electrically conductive bodies with the aid of direct current.

This principle is described in the literature and is widely used in practice. A workpiece with an electrically conductive surface made of metal or electrically conductive plastic is placed in an aqueous electrodeposition lacquer bath, connected as a cathode to a direct current source and then the lacquer on the surface is coagulated by the flowing current (EP-B-0066859, EP-A- 0 004090, DE-A-32 15 891). The electrocoating bath consists of an aqueous dispersion, e.g. Suspension or emulsion, or from an aqueous solution of one or more binders by at least partial salt formation with organic or inorganic

Neutralizing agents are made water-dispersible, from pigments, fillers, additives, solvents and conventional auxiliaries dispersed therein.

With these lacquer materials, smooth surfaces should be created after deposition and baking and cross-linking of the resulting film. These films are said to be rough and different underground surfaces cover evenly. They are used to create a homogeneous surface for the subsequent layers, which together should result in a high quality multi-layer coating. In practice, however, surface defects, in particular craters, or uneven surfaces frequently occur in the burned-in KTL film. The causes of these coating faults can be found in the electrocoat materials used, but it is often found that these malfunctions originate from impurities carried into the electrocoat bath. Examples of impurities from the coating material are gel particles from the production of binders, impurities in the pigments and impurities, for example oils or deposits, from devices which are used to produce the coating compositions. Foreign substances that are subsequently introduced over the substrates to be coated are, for example, deep-drawing greases,

Corrosion protection greases, seam sealing materials and substances from the pretreatment.

Another class of contaminants are those that are deposited on the non-crosslinked paint film after the electrodeposition coating has been removed from the air, for example silicone-containing aerosols, and lubricants from the transport systems which are necessary for moving the parts to be coated.

These substances get onto the paint film before baking and then cause surface defects, e.g. due to incompatibilities, such as e.g. Crater. A possible damage to the surface by these materials cannot be foreseen, but must be determined by experiments.

These surface defects require extensive reworking in order to achieve a smooth surface for the subsequent layers. Therefore, in order to ensure continuous production, it is necessary to avoid this type of surface disturbance. Since it is difficult to prevent the diverse causes of craters, attempts are generally made to avoid crater formation by adding additives. Silicone oils, for example, are known as additives to avoid craters. When used in the corresponding layer, these can suppress crater formation, but often lead to severe surface defects in subsequent layers. It should also be noted that the

Subsequent layers adhere poorly to such base layers. Therefore, these additives are not suitable for KTL layers.

Therefore, attempts have been made to find other additives that do not contain silicone in order to avoid these frequent surface defects. US-A-4,810,535 describes polyoxyalkylene polyamine-epoxy resin reaction products as an additive to cathodic dipstick systems. This is to avoid craters. EP-A-0 324 951 describes polyoxyalkylenepolyaines as additives to KTL baths in order to obtain trouble-free film surfaces. DE-A-38 30 626 describes modified acrylates as additives for KTL baths, which can be added to the paint material in a way that can be neutralized or not neutralized. In this case too, various types of surface disturbances should be avoided. All of these materials show the property that they have to be used in larger amounts in order to achieve a good anti-crater effect. The difficulty arises here that liability to subsequent layers, e.g. Filler or underbody protection materials, deteriorates significantly and surface roughness and flow problems occur, which can occur even with small amounts. This leads to bad ones

Results in stone chip tests or the corrosion protection of critical body parts is deteriorated. In addition, general course disorders then often occur, which negatively influence the quality of the subsequent layers.

EP-A-0 301 293 describes cathodic electrocoating baths which contain, as an additive, a homo- or copolymer of an alkyl vinyl ether with a C ₂ -C ₄ -alkyl radical. The Ho o- or copolymers are prepared by polymerization of an alkyl vinyl ether, optionally together with up to 20 wt .-% of other copolymerizable monomers. The polymers have weight average molecular weights of 500 to 100000 and are in Quantities from 10 to 10000 pp, based on the weight of the finished KTL bath. The disadvantages of the anti-cratering agents listed above also occur here, in particular if the anti-cratering agent is used in the upper quantity range. At the

Burning in the KTL exudes the anti-crater agent, the adhesion of subsequent layers is disturbed. If the anti-cratering agent content in the KTL is in the lower range or below it, these anti-cratering agents have an undesirable potential leading to surface defects. Another problem of particular importance when using the anti-cratering agent according to EP-A-0 301 293 in KTL baths is that coating agents applied in the form of plastisols, for example undercoat protective layers based on PVC, are separated from and separated from these KTL baths burned-in layers of paint slip off during the gelling.

The object was therefore to provide a surface-improving agent, in particular an anti-crater agent, for KTL systems, which has a good anti-crater effect, has good follow-up layer adhesion, the slipping off of follow-up layers, in particular on the

Base of plastisols, avoided and can also be used in larger quantities. The anti-cratering agent should not have any effect leading to surface defects if its content in KTL baths assumes low values.

It has been shown that this object can be achieved by adding certain substances produced by polymer-analogous reaction to KTL baths.

The invention therefore relates to additives for cathodically depositable aqueous electrodeposition baths in the form of randomly built polymers or copolymers of the schematic formula obtained by polymer-analogous reaction

4 (CH ₂ CHX), (CH ₂ -CH0R) _b (CH, CH0R '), (I)

wherein a = 0 to 20 mol%, b = 50 to 99 mol%, c = 0 to 50 mol%, d = 0 to 50 mol%, n = 5 to 1500, preferably between 10 and 200,

X = a substituent different from OR and OR ', preferably halogen, -COOR "or -aryl,

R = C, - to C ₁₀ alkyl, 0

R '= H and / or -C-R ",

R "= C _r to C ₃ alkyl and the sum of c + d results in at least 1 mol%.

The expression "random polymer or copolymer" or "statistical polymer or copolymer" used in the present description and the patent claims means that individual and / or blocks of the mol% indications a, b, c, d and e labeled molecule portions are statistically distributed over the total molecule of the polymers or copolymers. For simplification, the term "polymer" is used here instead of "polymer or copolymer".

The polymers according to the invention can be produced in various ways. For example, it is possible to prepare the polymers (1) by polymer-analogous conversion of randomly structured polymers of the following schematic formula

in which

a = 0 to 20 mol%, b '= 80 to 100 mol%, n = 5 to 1500, preferably between 10 and 200, X = a substituent different from OR and OR', preferably halogen, -COOR "or - Aryl, R = C, - to C, -alkyl with acidic compounds. The reaction can be carried out under various conditions, for example in an organic medium or preferably in the presence of water. For example, it is possible to work under increased pressure and / or with an increase in temperature.

A reaction of the polymeric starting material (II) with water and acid, such as e.g. organic carboxylic acids and their derivatives. Organic solvents may optionally be present. The acids can be used alone or in a mixture with other catalysts.

Halogens are given as examples for the substituent X in the formula (I) and in the formulas (II) and (III) below. Examples of usable halogens are fluorine, chlorine and bromine. Preferred examples of the aryl group in the meaning of X are phenyl and substituted phenyl radicals, such as C 1 -C 4 -alkylated phenyl radicals.

In the preparation of the polymers of the formula (I), the ratio of b to c to d and, if appropriate, the ratio R '= H to R' = COR "in the polymer (I) can be controlled by suitable selection of the various process parameters in the polymer-analogous reaction .

For example, the choice of the starting material, the type and amount of acid in the reaction mixture, the proportion of water in the reaction mixture and the choice of reaction conditions (temperature, pressure, reaction time, reaction regime) have a controlling influence. For example, temperatures below 150 ^° C, preferably from 80 to 140 ^° C can be used. The pressure is, for example, normal pressure, but it is also possible, for example, to work at higher pressures, up to 6 bar, preferably below 6 bar.

In addition to typical Lewis acids, such as, for example, boron trifluoride, inorganic acids, such as, for example, hydrogen iodide, hydrogen bromide, hydrogen chloride, sulfuric acid, nitric acid, and phosphoric acid, but in particular organic acids, such as, for example, formic acid, acetic acid, are suitable as acids for the polymer-analogous conversion of the polymers (II). Oxalic acid, Lactic acid suitable. The acids can be used in aqueous solution, but also in organic solution, such as, for example, gaseous acids, such as hydrogen chloride gas, dissolved in an organic solvent. The acids can be used individually or in a mixture. Preferred acids are those which are used as neutralizing agents in conventional KTL baths. It is not necessary to remove such acids from the reaction mixture prior to the use according to the invention of the polymer (I) produced by the polymer-analogous reaction of the polymer (II) in the KTL. Examples include acetic acid, formic acid,

Lactic acid. Without being bound by theory, it is believed that Lewis acids generally have a catalytic effect and organic acids can act as catalysts and / or also as reactants.

The acids are used, for example, in amounts of 0.1 to 100% by weight, based on the weight of the polymer (II), while the amount of water in the reaction mixture is preferably, for example, 5 to 100% by weight, based on the weight of the polymer ( II) is. If the acid is to have a catalytic effect in particular, the proportion of acid in the reaction mixture can be chosen to be low, for example between 0.1 and 10% by weight, based on the weight of the polymer (II). If R 'in the target polymer (I) has the meaning of -COR "in part or in full, this is done by acylation using an organic C ₂ -C ₄ carboxylic acid, preferably acetic acid. A larger amount of the acid is preferably used, to the

Ensure acylation reaction. Then, for example, 10 to 100% by weight of carboxylic acid, based on the weight of the polymer (II), is used and the amount of water in the reaction mixture is preferably chosen to be low.

According to the invention, the polymers (I) produced by polymer-analogous reaction of polymers (II) with water and acid are particularly preferably used in KTL baths. The educt polymers of the schematic formula II used for this purpose are homo- or copolymers of vinyl ethers which can be prepared by free radical or cationic methods in accordance with the usual polymerization methods known to the person skilled in the art. For example, those in the 400

homopolymers or copolymers of vinyl ethers described at the outset in EP-A-0 301 293 can be used as starting polymer (s) (II).

The polymer (I) has a ratio of a: b: c: d = 0 to 20 mol%: 50 to 99 mol%: 0 to 50 mol%: 0 to 50 mol%. In polymer (I), a is preferably 0 mol%. The ratio of b: (c + d) in the polymer (I) is preferably 60 to 95 mol% to 5 to 40 mol%. The ratio of b: (c + d) and c: d in the polymer (I) can be influenced by the choice of the process parameters, which can easily be determined by a person skilled in the art on the basis of experiments. Thus, particularly in the case of the above-mentioned polymer-analogous reaction of polymers of the formula (II) with acids, the b / (c + d) and the c / d ratio are shifted to low values by measures such as the application of pressure (carrying out the polymer-analog Reaction in an autoclave), increased reaction temperature, long reaction time and shift in the reaction equilibrium due to the removal of reaction products. For example, in the polymer-analogous reaction of the polymer (II), a volatile alcohol ROH can be removed from the reaction equilibrium by distillation, if appropriate under vacuum.

The polymer-analogous reaction of the polymers (II) can be carried out with the aid of phase transfer catalysts or emulsifiers. However, such auxiliaries are preferably not added in the polymer-analogous reaction. It may be appropriate to carry out the polymer-analogous reaction in the absence of oxygen. In addition, conventional inhibitors, such as hydroquinone, can also be added in order to largely prevent free-radical side reactions.

The polymers (I) can alternatively, but less preferably, by polymer-analogous conversion of randomly structured polymers of the schematic formula

(CH ₂ CHX). (CH ₂ CH0R) _b (III)

can be obtained with water and base, whereby a = 0 to 20 mol%, b = 50 to 99 mol%, e = 1 to 50 mol%, n = 5 to 1500, preferably between 10 and 200,

X = a substituent different from OR and OR ', preferably halogen, -COOR "or -aryl, R = C _r to C ₁₀ alkyl, R ^ = C _r to C ₃ alkyl.

Organic and / or inorganic bases can be used as bases. Examples of these are organic amines, such as primary, secondary and tertiary amines, and hydroxides, such as alkali metal hydroxides, e.g. Sodium hydroxide and potassium hydroxide. The bases are generally used in catalytic amounts of 0.1 to 10% by weight, based on the weight of the polymer (III), while the amount of water in the reaction mixture is preferably 5 to 10% by weight, based on the weight of the polymer (III) is. The bases should preferably be removed from the reaction mixture before the polymer (I) is used in the KTL according to the invention. This can be done for example by distillation extraction or also by neutralization.

The polymers (I) prepared by polymer-analogous reaction are generally obtained as a reaction mixture with catalyst, water and / or organic solvent. It is convenient to organic

Remove solvents or inorganic salts from the mixture. However, carboxylic acids or water can remain in the reaction mixture since the generally small proportions in this mixture do not interfere with the KTL bath.

The polymers (I) which can be used according to the invention as surface-improving agents in KTL baths preferably have an OH number between 0 and 500 mg KOH / g, particularly preferably below 300, particularly preferably below 100. The polymers (I) can, for example, be C = C -Double bonds corresponding to an iodine number of 0 to 250, preferably less than 150, particularly preferably less than 100 contained. The olefinic double bonds can be isolated and / or conjugated in the polymer (I) available. They can be in teral or distributed along the main chain. The weight average molecular weight (Mw) of the polymers (I) is preferably between 500 and 100,000. The polymers (I) are essentially water-insoluble and become cataphoretic

Separation from the KTL baths according to the invention in the ratio of the solid bath also separated, i.e. they do not accumulate in the KTL bath. The polymers (I) have no membrane compatibility with regard to an ultrafiltration process coupled with the electrocoating, i.e. the ultrafiltrate is free of them.

The polymers (I) act as surface-improving agents if they are used in KTL systems in proportions of, for example, 10 to 10000 ppm, preferably from 100 to 7000 ppm, particularly preferably from 200 to 5000 ppm, based on the finished KTL bath .

Another object of the invention are cathodically depositable aqueous electrocoating baths which contain the usual binder systems suitable for cathodic deposition in addition to crosslinking agents, pigments, fillers, solvents and / or customary lacquer additives and additionally contain one or more polymers (I).

In the KTL deposition of the KTL baths according to the invention, smooth, crater-free and trouble-free surfaces are formed after baking (for example at temperatures from 110 to 190 ^° C.), which do not have any adhesion problems with the usual subsequent layers. Coating layers applied in the form of plastisols to the burned-in KTL layers, for example underbody protection layers, show good adhesion to the primer and do not slip during the gelling process. An undesirable uneven distribution in the layer thickness of the plastisol is certainly avoided. This is, for example, of essential importance in automotive painting, since KTL-primed bodies are also coated on vertical surfaces, such as wheel arches or in the sill area, with underbody protection plastisols, for example based on PVC. The KTL baths show excellent crater resistance. The craters caused by impurities are within wide limits reduced. Surprisingly, there are no additional surface defects if only small amounts of the anti-cratering agent are present. Amounts of the polymer (I) higher than 10,000 ppm can also be present without the occurrence of interfering effects, such as exudation or disturbances in the subsequent layer adhesion.

Cathodic electrocoating baths to which polymers (I) have been added according to the invention are distinguished by an extraordinary resistance to contamination by substances that cause craters.

According to the invention, customary electrodeposition coating baths can be used which consist of an aqueous solution or dispersion of cathodically depositable self- or externally crosslinking synthetic resins, optionally crosslinking agents, optionally customary pigments and / or fillers as well as other customary lacquer additives and auxiliaries and optionally organic solvents. The solids content of the KTL baths used according to the invention, which is calculated from binders, any crosslinking agent, pigments and / or fillers present, is, for example, 10 to 25% by weight, based on the total bath. The ratio of pigments and fillers to binder (plus any crosslinking agent present) is, for example, 0 to 0.7: 1, based on the weight. The organic solvent content is, for example, up to 10% by weight. If non-self-crosslinking binders that require a crosslinker are used, the ratio of binder / crosslinker is, for example, 90:10 to 60:40, in each case based on the weight of the solid resin.

For this purpose, the binders used in the KTL baths contain common basic resins with basic groups, which can contain sulfur, nitrogen or phosphorus. Nitrogen-containing basic groups are preferred. These groups can be quaternized, or they are converted into ionic groups using a conventional neutralizing agent, such as, for example, organic monocarboxylic acids. Basic base resins are, for example, resins containing primary, secondary or tertiary amino groups, the amine numbers of which are, for example, 20 to 250 mg KOH / g. The weight average (Mw) of the molar mass of the base resins is preferably 300 to 10,000. In addition to -NH ₂ , -NRH, -NR ₂ and -H, for example also -S ^* R ₂ , -PΕ ₃ , where R represents, for example, an alkyl radical having 1 to 4 carbon atoms and the radicals R can be the same or different. Nitrogen-containing basic groups are preferred. The inorganic and / or organic acids theoretically known and used in practice can be used as neutralizing agents which supply anions in the aqueous binder solutions. In practice, monovalent acids are mainly used, which cause the binder to be water-dilutable. Formic acid, acetic acid, lactic acid or alkyl phosphoric acids are preferably used.

Base resins are e.g. Amino acrylate resins, amino epoxy resins, amino epoxy resins with terminal double bonds, amino polyurethane resins, amino group-containing polybutadiene resins and modified epoxy resin-carbon dioxide-amine reaction products.

These base resins can be self-crosslinking or they are used in a mixture with known crosslinking agents. Examples of such crosslinkers are aminoplast resins, blocked polyisocyanates, crosslinkers with terminal double bonds, polyepoxide compounds or crosslinkers which contain groups capable of transesterification and / or amidation.

Examples of base resins and crosslinking agents which can be used in cathodic dip coating (KTL) baths and which can be used according to the invention are described in EP-A-0 082 291, EP-A-0 234 395, EP-A-0 209 857, EP -A-0 227 975, EP-A-0 178 531, EP-A-0 333 327, EP-A-0 310 971, EP-A-0 456 270, US-A-3 922 253, EP-A -0 261 385, EP-A-0 245 786, DE-A-33 24 211, EP-A-0 414 199, EP-A-0 476 514. These resins can be used alone or in a mixture. The electrocoat materials of the invention can contain pigments. Typical pigments and / or fillers such as carbon black, titanium dioxide, iron oxide red, kaolin, talc or silicon dioxide can be used as pigments for the KTL deposition. The pigments are preferably dispersed and rubbed into conventional pigment paste resins. Such resins are described for example in EP-A-0 469 497. The production of the pigment pastes and the production of the cathodic dip baths are familiar to the person skilled in the art. For example, pigments and / or fillers can be dispersed in customary grinding binders and then ground on a suitable aggregate, for example a bead mill. The pigment paste thus obtained can then be added to the KTL binders in various ways. For example, it is mixed with the KTL binders. The KTL coating bath can then be made from this material by diluting it with deionized water. An example of a different procedure first converts the neutralized and thus water-soluble binders or binder mixtures into a dispersion. This is further diluted with deionized water and then the aqueous pigment paste is added. A KTL bath that can be coated is also obtained in this way. Such electrocoat baths contain not only pigments and fillers but also necessary neutralizing agents; They can additionally contain solvents customary for KTL baths and / or further additives or auxiliary substances customary in paint, such as defoamers or catalysts.

The surface-improving agent of the formula (I) can be added to the electrocoating baths from the outset during production, or else subsequently directly when used for electrocoating.

The anti-crater additive used according to the invention can, for example, be dispersed in the binder mixture before or after neutralization and can be transferred together with the binder into the dispersion phase. An example of another procedure is that after the binder has been transferred into the water phase, the additive is mixed with an auxiliary, such as, for example, part of the dispersible one neutralized resins or neutralized paste resin or a suitable solvent of the dispersion. After thorough homogenization, the additive is stably incorporated.

Another possibility is to incorporate the anti-crater additive into any pigment paste used. This is advantageously done before the pigment paste is ground, so as to ensure that the additive is homogeneously distributed in the pigment paste. The pastes thus obtained are stable and show the desired properties after addition to the electrocoating bath.

It goes without saying that the polymer (I) which can be used according to the invention as an anti-cratering agent in cathodic electrocoating materials can also be used in a mixture with one or more other anti-cratering agents which are suitable for use in cathodic electrocoating materials.

Examples of such substances which can be used as anti-cratering agents in cathodic electrocoating baths are copolymers of alkyl vinyl ethers, polyesters with beta-hydroxyalkyl groups, polyoxyalkylene polyamines, polyether urethanes with amine groups in the molecule, cationic acrylate resins, cationic microgels, polymer microparticles and / or polyoxyalkylene resin-polyamine-epoxidation products.

The sum of the anti-cratering agents used is preferably kept as low as possible, preferably below 2% by weight, based on the finished KTL bath. If the amount is too large, there may be disadvantages in the paint properties.

It is possible to add the anti-crater additive to KTL baths ready for coating. For this purpose, it is expediently converted into a water-dilutable form, for example by means of solvents, water-dispersible emulsifiers, water-dilutable binders or water-dilutable paste resins. This procedure is particularly suitable if it has been found that when working with a KTL-Bad surface disturbances occur. After the addition of the anti-cratering agent according to the invention, these disorders are then eliminated.

Various substrates can be coated under the usual conditions from the electrocoat baths provided with anti-cratering agents according to the invention. After baking, they have a smooth, crater-free surface. Due to the anti-crater additive used according to the invention, other varnish properties, such as e.g. Corrosion protection, stone chip resistance, subsequent layer adhesion, not affected.

Slipping of plastisol coating layers applied to the burned-in KTL layers, e.g. Underbody protective layers, during the gelling process is avoided.

As an alternative to their use as surface-improving additives in the KTL bath, the polymers (I) can also be used for the aftertreatment of KTL-Fi en according to the procedure of the as yet unpublished application P 4 303 812 by the same applicant. To this end, o / w emulsions (oil-in-water emulsions) of the polymers (I) are prepared. Moist, non-crosslinked KTL coatings which have been deposited from KTL baths free of polymers (I) are brought into contact with these emulsions before the subsequent baking. The surface-improving effect when using the polymers (I) as an o / w emulsion, in particular the anti-crater effect, corresponds entirely to that when using the polymers (I) as part of the KTL bath. Here too, the adhesion to subsequent layers is perfect and the slipping of plastisols during the gelling process is avoided.

The anti-cratering agent used according to the invention is therefore particularly suitable in the motor vehicle sector, for example for priming motor vehicle bodies or motor vehicle body parts, with the subsequent multilayer paint structure. Production of the polymers (I) by polymer-analogous reaction

example 1

A two-phase mixture of 1200 g of a commercially available polyvinyl vinyl ether (Lutonal A 25 ^R from BASF AG), 400 g of glacial acetic acid and 200 g of deionized water is heated to 100 ^° C. for 8 hours with stirring and inert gas flushing. 102 g of ethanol are distilled off. The material obtained forms a stable single-phase system.

Example 2

Example 1 is repeated with the difference that 100 g of glacial acetic acid, 50 g of deionized water and 10 ml of a 41% solution of

Boron trifluoride can be used in glacial acetic acid. 132 g of distillate are obtained.

Example 3

Example 1 is repeated with the difference that 50 g of glacial acetic acid and 72 g of deionized water are used. 72 g of distillate are obtained.

Example 4

Example 1 is repeated with the difference that no glacial acetic acid, 50 g of deionized water and 2 ml of the boron trifluoride solution from Example 2 are used. The single-phase system obtained has an iodine number of 53.

Production of a pigment paste

Example 5

223 parts of a paste resin according to EP-A-0 469 497 AI Example 1 (55%) are mixed with 15 parts of acetic acid (50%) under a high-speed stirrer %), 30 parts of a commercial wetting agent (50%) and 374 parts of deionized water.

5 parts of carbon black, 5 parts of fumed silica, 25 parts of dibutyltin oxide powder, 38 parts of lead silicate and 560 parts of titanium dioxide are added. With approx. 225 parts of deionized water, the mixture is adjusted to approx. 50% solids and ground on a pearl mill. A stable pigment paste is created.

Manufacture of anti-crater preparations

Comparative experiment A

42.5 parts of the paste resin according to EP-A-0 469 497 Example 1 (55%) are mixed with 23 parts of the commercially available polyvinyl vinyl ether from Example 1 and 2.3 parts of acetic acid (50%) and diluted with 43.6 parts of deionized water .

Example 6a

The procedure is as in Comparative Experiment A, with the difference that the polyethyl vinyl ether is replaced by 32 parts of the anti-cratering agent from Example 1 produced by the polymer-analogous reaction.

Examples 6b to d

The procedure is as in Comparative Experiment A, with the difference that the polyethyl vinyl ether is in each case replaced by the same amount of the anti-cratering agents from Examples 2 to 4 produced by the polymer-analogous reaction.

Production of a cathodic dip lacquer

Example 7a a) 832 parts of the monocarbonate of an epoxy resin based on bisphenol A (commercial product Epicote 828) are mixed with 830 parts of a commercially available polycaprolactone polyol (commercial product CAPA 205) and 712 parts of diglycol dimethyl ether and at 70 to 140 ^° C. with about 0.3% BF ₃ etherate reacted until an epoxide number of 0 is reached. 307 parts of a reaction product of 174 parts of tolylene diisocyanate (2.) Are added to this product (solids 70%, 2 equivalents of carbonate) at 40 to 80 ^° C in the presence of 0.3% of Zn acetylacetonate as catalyst

Equivalents of NCO) with 137 parts of 2-ethylhexanol with the addition of 0.3% benzyltrimethylammonium hydroxide (Triton B) with an NCO content of approximately 12.8%. It is reacted up to an NCO value of approximately 0 and then adjusted to approximately 70% solids with diglycol dimethyl ether.

b) To 1759 parts of a biscarbonate of an epoxy resin based on bisphenol A (commercial product Epicote 1001 ") will be at 60 to 80 ^° C 618 parts of a reaction product of 348 parts of tolylene diisocyanate (80% 2,4 isomer; 20% 2,6 Isomeres) with 274

Parts of 2-ethylhexanol with addition of 0.3%

Benzyltrimethylammonium hydroxide as a catalyst with a residual NCO content of 12.8% slowly added with the catalysis of 0.3% of a non-ionic emulsifier (Triton B ^s ). The reaction is continued up to an NCO value of approximately 0. The product has one

Solids content of 70%. To 860 parts of bishexamethylenetriamine in 2315 parts of methoxypropanol, 622 parts of the reaction product of 137 parts of 2-ethylhexanol with 174 parts of tolylene diisocyanate are added at a temperature of 20 to 40 ^° C. with benzyltrimethylammonium hydroxide catalysis (0.3%) (NCO-

Content about 12.8%) and implemented up to an NCO content of about 0. Then 4737 parts of the reaction product b) and 3246 parts of the reaction product a) (each 70% in diglycol dimethyl ether) are added and reacted at 60 to 90 ^° C. The reaction is terminated at an amine number of about 32 mg KOH / g. The resulting product is distilled off in vacuo to a solid of about 85% and after neutralization with 30 mmol formic acid / 100 g resin converted into an aqueous dispersion (solids 40%).

4.5 parts of formic acid (50) and 1760 parts of deionized water are added to 815.5 parts of the dispersion obtained above. 420 parts of pigment paste according to Example 5 are added with thorough stirring.

Example 7b

1.5 parts of a crater-forming substance (Anticorrit 15 N-68, from Fuchs Mineralölwerke, Mannheim) are added to the cathodic dip coating from Example 7a and homogeneously distributed overnight. For better incorporation, the crater-forming substance can be diluted beforehand with a mixture of xylene and butyl glycol.

Manufacture of cathodic electrodeposition paints

Examples 7c to g

25 parts of anti-crater preparation according to comparative experiment A and inventive examples 6a to 6d according to the following table are added to the cratered lacquer from example 7b and homogenized well.

Conventional phosphated steel sheets are coated from these cathodic lacquer baths (dry film thickness approx. 20 μ) and baked for 15 minutes at an object temperature of 165 ^° C. The behavior regarding crater formation and the slipping behavior of PVC materials applied to the burned-in KTL layer are assessed. For this, approx. 10 g of the PVC material are applied and the vertical sample sheet is baked for 10 minutes at an object temperature of 140 ^° C. The slip behavior is assessed, expressed as the distance in centimeters by which the PVC material has migrated. The PVC material does not change its outer shape, so that the route through

Measure the difference between the bottom edge of the PVC material before and after the branding can be determined. The PVC materials are common underbody protection materials from Dr. A. Stankiewicz GmbH, Celle and Teroson GmbH, Heidelberg.

Example crater slip behavior (cm)

7a ¹ ) little 0 7b ² ) many 0

7c (7b + compare A) none 4

7d (7b + 6a) no 0

7e (7b + 6b) no 0

7f (7b + 6c) none 0 7g (7b + 6d) none 0

') without anti-crater and without crater-causing substance ² ) without anti-crater

The corrosion protection results and the technological properties of the different approaches are comparable and give good results.

Claims

Claims:

1) Additive for cathodically depositable aqueous electrocoating baths in the form of a polymer of the schematic formula

J. (CH, CHX) _a (CH ₂ CH0R) _b (CH ₂ CH0R ') _c (I)

wherein the parts of the molecule identified by the indices a, b, c, and d are statistically distributed over the entire molecule

a = 0 to 20 mol%, b = 50 to 99 mol%, c = 0 to 50 mol%, d = 0 to 50 mol%, n = 5 to 1500,

X = a substituent different from OR and OR,

R = C ₁ to C _1Q alkyl,

R '= H and / or -COR ", R" = C. - to C ₃ alkyl and the sum of c + d gives at least 1 mol .-%.

2) Additive according to claim 1, obtainable by polymer-analogous reaction of randomly structured polymers of the schematic formula

wherein a, n, X and R are as defined in claim 1 and b '= 80 to 100 mol%,

with acidic compounds. 3) Process for the preparation of the additives according to claim 1 or 2, characterized in that one uses a statistically constructed polymer of the schematic formula

CH.CHX), (CH.CH0R)

! ^■ 'Ü wherein a, b', n, X and R as defined in claims 1 and 2 are reacted with acidic compounds.

4) Process for the preparation of the additives according to claim 1 or 2, characterized in that one uses a statistically constructed polymer of the schematic formula

-f (CH, CHX) _a (CH, CH0R) _b (CH, CH0C0R) _e ; (III)

// where a, b, n, X, R and R are as defined in claim 1 and e =

1 to 50 mol%, reacted with bases in an aqueous medium.

5) Additive and method according to one of the preceding claims, wherein the polymer of the schematic formula (I) has a weight average molecular weight (Mw) of 500 to 100000, an OH number of 0 to 500 and C = C double bonds corresponding to an iodine number of 0 up to 250.

6) Cathodically depositable aqueous electrodeposition coating baths which contain conventional binder systems suitable for cathodic deposition in addition to any crosslinking agents, pigments, fillers, solvents and / or customary lacquer additives which additionally contain one or more additives according to one of the preceding claims or prepared according to one of the preceding claims .

7) Cathodic aqueous electrodeposition baths according to claim 6, containing 10 to 10,000 ppm of the additives, based on the finished bath. 8) Use of the additives according to one of claims 1, 2 or 5 or produced by the method of claims 3, 4 or 5 in cathodic electrodeposition baths.

9) Use of the additives according to one of claims 1, 2 or 5 or produced by the method of claims 3, 4 or 5 as an anti-cratering agent for cathodically deposited coatings from electrocoating baths.

10) Use of the additives according to one of claims 1, 2 or 5 or produced by the method of claims 3, 4 or 5 as anti-cratering agent without slipping effect of subsequent layers for coatings deposited cathodically from electrocoating baths.

11) Use of the additives according to one of claims 1, 2 or 5 or produced by the method of claims 3, 4 or 5 for coatings cathodically deposited from electrocoating baths in the production of multi-layer coatings.