AU617152B2 - Process for coating electrically conductive substrates, substrates so obtained, and aqueous electrophoretic enamel baths - Google Patents

Abstract

A cathodic electrophoretic enamelling process is characterized in that the electrophoretic enamelling bath contains at least 7.5 wt. % of a polyoxyalkylene polyamine or a mixture of several polyoxyalkylene polyamines of differing chemical structures, the percentage by weight being expressed with respect to the total binder content in the electrophoretic enamelling bath.

Description

GRIFFITH HACK CO___ PATENT AN D TRADE MARK, ATTORNEYS M EIBOU R NE -S Y DNE Y P ERT H

PCT

0 INTERNATIONALE ANf' INTERNATIONALE ZUE (51) Intern~ationale Patentkiassifikaloii C09D 3/58, 5/44 (21) Interriationales Akienzeichen: ONI DATE 11/08/89 APPLN. ID 30529 89 01f89 06 NUMBER PCT/EP88/01164 11) Int nat~l Vc Z ntichungsnuimcr WO 89/ 06673 (43) Internationales 'Verffentlichungsdatum: 27. Jul! 1989 (27,07.89) PCT/EP88/Pl 164 (22) Internationales Anmeldedatum: Dezember 1988 (15,12,88) (31) Priori 1atsa ktenzeichen: (32) Prioritatsdatum: P 38 01 787,3 (74) Anwalt: LEIFERT, Elmar; BASF' Lacke Farben AG, Postfach 61 23, D-4400 MWnster (DE).

(81) Bestimnmungsstaaten: AT (europiiisches Patent), AU, BE (europatisches Patent), BR, CH (europgiisches Pa-, tent), DE (europiiisches Patent), FRI (europ~isches Patent), GB (europ~isches Patent), IT (europ~isqhes Patent), JP, KR, LU (europfiisches Patent), NL (europ~qisches P-tent), SE (europaiisches Patent), US.

Verbffientlicht Alit in terna tion alern Re'cherch enberichi.

22, Januar 1988 (22,01.88) DE 1(33) Prioritlitsland, (71) Aninelder (ffir alle Bestimnnngsstaaten at, sser US); BASF LACKE FARBEN AKTIENGESELL- SCHAFT [DE/DE]; Max-Winkelmann'Strage 80, D- 4400 Manster (DE).

(72) Ertinder;und Erfinder/Anmelder (nur ,iir US) OTT, Gilnther [DE/ DE]; Yon-Holte-Stra~c 101 a, D-4400 MOnster (DE), REITER, 'Ido [DE/DE]; Regerstrake 22, 0.4404 Telgte JOUCK,, W~1tpr [DE/DE], GrOner Weg 7, D-4400 MOnster SANTURE, David, J, [US/ DM Hummelbrink 13, D-4400Mnse

(D)

R ,HL, Dieter [DE/DE]; Ellttorfstrnae 57, D-4400 MOnster (DE (54)Til; PROCESS FOR COATING ELECTRICALLY CONDUCTIVE SUBSTRATES, SUBSTRATES SO OBTAI- NED, AND AQUEOUS ELECTROPHORETIC ENAMEL BATHS (54) Bezeichnung: VERFAHREN ZUR BESCHICH-TUNG EL.EKTRISCH- L.EITFAI-IGER SUBSTRATE, NACH- DIESEM VERFAI4REN BESCHICHTETE SUBSTRATE UND WASSRIGE ELEKTROTAUCH-I

LACKBADER

(57) Abstract A cathodic electrophoretic enamelling process is characterized in that the electrophoretic enamelling bath contains at least 7,5 wt, 1/o of a polyoxyalkylene polyamine or a mixture or several polyoxyalkylene polyamines of differing chemit cal structures, the percenta-)e by weight being expressed with respect to the total binder content in the electrophoretic en4 amelling bath, (57) Zusammenfassung Die Erfindlung betrlfft ein kathodisches Elektrotauchlackierverfahren, das dadurch gekennizelchttet 1st, dall das Iclktrott~uchlackbad mlndestens 7,5 etlnes Polyoxyalkylenpolyamins oder eines Gemisches aus mehreren Polyoxyalkylenpolyarninen mit unterschledllchen chemischen Strukturen enthillt, wobei sich die Cew.,o'Angabe auf die im Elektro.

tauchlackbad enthaltene Gesamntmeqc, an Bindernitteln bezieht,

JL

1 Process for coating electrically conducting substrates, substrates coated by this process and aqueous electrocoating baths According to the present invention there is provided a process for coating electrically conducting comprising immersing the substrate in an aqueous electrocoating bath which contains a resin capable of being cathodically deposited, connecting the substrate as cathode, depositing a film on the substrate by the action of direct current, removing the substrate from the electrocoating bath and baking the deposited paint film, o-o wherein the electrocoating bath contains at least 7.5% by weight of a polyoxyalkylenepolyamine or a mixture consisting S. of several polyoxyalkylenepolyamines of different chemical structures, the percentage by weight referring to the total S:0Q 0 amount of binders contained in the electrocoating bath.

i The invention also relates to substrates coated by the process according to the invention and to the electrocoating .4 baths employed in the process according to the invention, o i 2 The cathodic electrocoating process described above is a painting process frequently used primarily for priming, in particular for priming of automotive bodies.

i Processes of the type described above have been disclosed, for example, in the following patents: DE-OS 3,518,732, DE-OS 3,518,770, DE-OS 3,409,188, EP-A 4,090 and EP-A 12,463.

I Using processes of this type, it is possible to achieve i coatings of excellent quality. However, surface defects S A 10 (particularly craters), well known to a person skilled in the art, often occur in the baked paint film.

1 Many attempts have been made to suppress the occurrence of surface defects by adding additives. It is true that the surface defects may be eliminated in this manner, 1 15 but, instead, problems due to adhesion failure usually appear in the overcoated paint films (for example filler and top coat 1 Problems of this sort occur especially in overcoated paint films containing alkyd resins as binders.

The object forming the basis of the present invention is to make available a novel process in accordance with the preamble to patent claim 1. The novel process should overcome or reduce, in particular, the problems outlined above, associated with the present state of the art.

3 Surprisingly, this object is achieved by a process in accordance with the preamble of patent claim 1, wherein the electrocoating bath contains at least 7.5 by weight of a polyoxyalkylenepolyamine or of a mixture consisting of several polyoxyalkylenepolyamines of different chemical structures, the percentage by weight referring to the total amount of binders contained in the electrocoating bath.

SThe advantages achieved by the invention are essentially to be found in the fact that it is possible, using the process according to the invention, to obtain paint films which, compared with the paint films of the present state of the art, exhibit fewer and/or more faintly pronounced surface defects and do not give rise to defects due to S 15 adhesion failure in overcoated paint films, especially in overcoated paint films containing alkyd resins as binders.

Further important advantages achieved by the process according to the invention lie in the fact that, compared with the present state of the art, the paint films obtained by the process according to the invention possess greater film thicknesses and greater flexibility.

US-PS 3,975,250 discloses cationic reactive plasticizers, suitable for use in electrocoating baths, which are prepared by the reaction of partly blocked polyisocyanates with polyoxypropylenediamines. However, an average person A skilled in the art, faced with the object forming the

I

4 basis of the present invention, is unable to infer from US-PS 3,975,250 any information for achieving the object.

US-PS 4,423,166 discloses an eLectrocoating process in accordance with the preamble to patent claim 1, wherein the electrocoating bath contains as anticratering agent an adduct of a polyoxyalkylenepolyamine and a polyepoxide.

It is true that the paint films obtained by the process discLosed in US-PS 4,423,166 exhibit a Lower tendency for surface defect formation, but they give rise to defects due to adhesion failure in the overcoated paint films.

Such defects occur especially in overcoated paint films containing aikyd resins as binders.

i V The advantages achieved by the present invention are all the more surprising, since US-PS 4,423,166, column 18, describes electrocoating baths which contain up to 7.0 by weight, based on the total amount of binders contained in the electrocoiting bath, of a polyoxyalkylenepolyamine, Sbut produce paint films with pronounced surface defects (cf. Table I in US-PS 4,423,166).

Electrocoating baths for cathodic electrocoating are preferably prepared by first preparing an aqueous dispersion which contains a resin capable of being cathodically deposited and, if appropriate, a crosslinking agent and other customary additives such as, for example, antifoams S 25 e tc.

A pigment paste is then incorporated in this aqueous dispers ion.

The pigment paste consists of a ground resin and pigments and/or fillers. In addition, the pigment paste may also contain other additives such as, for example, plasticizers, wetting agents, antioxidants etc.

Examples of pigments and fillers which may be contained in the pigment paste, are: titanium dioxide, antimony oxide, zinc oxide, basic lead carbonate, basic lead sul- S .1 10 fate, barium carbonate, porcelain, clay, calcium carbonate, r aluminum silicate, silicon dioxide, magnesium carbonate, magnesium silicate, cadmium yellow, cadmium red, carbon black, phthalocyanine blue, chromium yellow, toluidyl red and hydrated iron oxide.

The preparation of pigment pastes is generally known and Sneed not be explained here in greater detail for example, O.H. Parker, Principles 'of Surface Coating technology, Interscience Publishers, New York (1965); R.L. Yates, Electropainting, Robert Draper Ltd., Teddington/ England (1966); H.F. Payne, Organic Coating Technology, volume 2, Wiley and Sons, New York (1961)).

The pigmert paste is added to the aqueous dispersion described above in such an amount that the finished electrocoating bath possesses the characteristics required for S 25 the depos ition. In most cases the weight ratio of pigment I, 7p7C 6or filler to the total amount of resin capable of being cathodically deposited and contained in the electrocoating bath is 0.05 to After the aqueous dispersion and the pigment paste have been combined and the combination adjusted to a suitable solids content, an electrocoating bath ready-for-use is obtained.

The electrocoating baths used according to the invention may in principle contain all the non-sel f-crosslink ing 6* 10 or self-crosslinking resins capable of being cathodically 6a deposited which are suitable for the preparation of

S

Selectrocoating baths. The electrocoating baths used according to the invention may also contain mixtures of lit, S' different resins capable of being cathodically deposited.

However, electrocoating baths containing cationic aminemodified epoxy resins as the resins capable of being cathodically deposited are preferred. Self-crosslinking as well as non-self-crosslinking cationic amine-modified epoxy resins are known. Non-self-cross inking cationic amine-modified epoxy resins are preferably used.

Cationic amine-modified epoxy resins are understood to be cationic reaction products from optionally modified polyepoxides and amines.

r. I -r 7 Potyepoxides are understood to be compounds which contain two or more epoxide groups in the molecule.

Particularly preferred components are compounds which may be prepared by reacting a diepoxide compound or a mixture of diepoxide compounds of an epoxide equivalent weight below 2000 Swith a compound monofunctionally reactive toward epoxide 10 groups under the given reaction conditions and containing a phenol or thiol group, or a mixture of such compounds, the components and being used in a molar ratio of 10:1 to 1:1, preferably 4:1 to 1.5:1, and the reaction of the component with the component being carried 15 out at 100 to 190 C in the presence or absence of a catalyst (cf. DE-OS 3,518,770).

Other particularly preferred components are compounds which may be prepared by a polyaddition of a diepoxide compound and/or a mixture of diepoxide compounds, if desired in conjunction with at Least one monoepoxide compound, to an epoxy resin in which the diepoxide compound and initiator are incorporated in a molar ratio greater than 2:1 to 10:1, the said polyaddition being carried out at 100 to 195°C in the presence of absence of a catalyst and initiated by a monofunctionally reactive initiator 'A carrying either an alcoholic OH group or a phenolic OH yr -8group or an SH group (cf. DE-OS-3,518,732).

The poLyepox ides which may be used for the preparation of the particularly preferred components and may even themselves be used as the components are poLygLycidyL ethers of polyphenols prepared from polyphenols and epihaLohydrins. The use of bisphenoL A and bisphenoL F, for example, as the poLyphenoLs is particuLarly preferred.

in addition, 4,4t -dihydroxybenzophenone, bis(4-hydroxy- 0 0 0 phenyl)'1,1-ethane, bis(4-hydruxyphenyL)-1,1-isobutane, bis(4-hiycroxy-tert-butyLphenyL)-2,2-propane, bis(2hy droxynaphthyL )methane, 1,S-dihydroxynaphthalene and phenollic novoLak resins are also suitable.

Other suitable poLyepoxidles are poLygLycidyL ethers of ft poLyhydric alcohols, such as, for example, ethylene gLycol, diethyLene g~ycoL, triethyLene glycoL, 1,2-propylene gLycoL, 1,4-propylene glycol, 1,5-pentanedioL, 1,2,6hexanetrioL glycerol and bis(4-hydroxycycLohexyL propane.

PoLygLycidyL esters of polycarboxyLic acids, such as, for exampLe, oxal ic acid, succinic acid, gLutaric 4cid, terephthalic acid, 2,6-naphthalenedicarboxyLic acid and', dimerized LinoLeic acid may be a~so used. GLycidyl adipate and gLycidyL phthaLate are typical exampLes.

other sui tabLe compounds are hydantoin, epox ides, epox id ized PoLybutadiene and poLyepoxide compounds .hich are obtained ft.

UVt et -9by epox idation of an oLef inicaL Ly unsaturated al iphatic compound.

Modified potyepoxides are understood to be poLyepoxidles in which some of the reactive groups have been reacted with a modifying compound.

Examples of modifying compounds are: a) compounds containing carboxyl groups such as saturated ,or unsaturated monocarboxyLic acids for example benzoic acid, L inseed fatty ac id, 2-e thyL hexanoic ac id, versat ic acid) aL iphat ic,. cyQloaL ipha t ic and/or aromatic dicarboxyL ic acids of various chain Lengths (for exampLe adipi, acid, sebac ic ac id, isophtha',ic ac id or dlimer ic f atty ac ids) hydroxy L kyL carboxyL ic $Its, a ci ds for examp~e lact ic ac id, d imethyLoLprop ion ic a c id) as weL L as polyesters containing carboxyL groups, or b) compounds conta iriing am ino groups, such as diethy(amine or ethyL hexy~am ine or di am ines w ith secondary amino groups, f or example NN I-diaLkYL alkyLened iamines such as dime thylethyLened iam ine, N,N I -d iaL kyLpoLyoxyaLkyLeneamines such as NONH -d imnethy(PoLyoxypropyleneliamine, cyanoaLkytated aLkylenediam ires such as bis- N,N I -cyanoethyLethyLenediamine, cyanoaL kyLatod poLyoxyaL kyLene am lnes such as b is-N41' I-cyanoe thytpoLyoxy- N' -4Proo~yLenediamine, po(yiniinoam ides such ats for OxamoLe, versamidles, in part icular reaction products containing terminal amino groups, obtained from diamines (for example hexametryLi-nediamine), polycarboxytic acids, particularLy dlimeric fatty acids, and monocarboxyL ic acids, in particuLar fatty acids, or the reaction product of one mole of dliaminohexane with two moles of a monoglycidlyl ether or monogLycidy( ester, especiaLy glycidyl esters of a-branched fatty acids such as versatic acid, or c) compounds containing hydroxy( groups such as neopenty(glycoL, bis-ethoxyLatedl neopentyLglyco(, neopentyl qlycoL hydrrxyp ivaLate, dimethylhydanto in-N,N -d jethanoL, hexane-1,6-liol, hexane-2,5-dipL, 1,4-bis (hydroxymethyl)- '~"cycLohexane, 1,1-isopropyLidene-'bis(p-phenoxy)-2propanoL, trim ,th iolpropane, pentaorythrito( or amino a alcohols such cs triethanoLamine, methyldiethanoLamine or z4kyLketimines containing hydroxyl groups, such as aminomethy~propanedioL-1,3-amethyL isobutylketimine or tris(hydroxymethyL)aminomothanecyc~ohexanoneketimine, as we(L as, polyqlycoL ether$, po~yester poLyals, po~yether poLyols, polycaproLactone po~yoLs, poLycaproa (actam polyols of various functionaLities and rnoLecuLar weights, or d) saturated or unsaturated fatty acid methyl esters which 2$ are transesterifled with the hydroxyL groups of the epoxy resins in the 0ro~zence of sodium methyLate.

Primary or -'econdary amines and their salts, salts of tertiary amines or mixtures of these compounds may be used as the component Water-soluble amines are preferably used as the component Examples of suitable amines; are monoaLkyLamine,, and dialkylamines, such as methyLamine, ethylamine, propyLamine, but)'Lamine, dimethylaniine, diethyLamine, diprqpy(amine, methyLbutyLamine etc. ALkanolamines, such as, *for exampte, methytethanolamine and dliethanolamine may also be used as components Ketimines of poLyamines with primary and secondary amino groups may also be used as the component Fur thermo r e, d ia( ky (am ino a Lkyt amines, such as, for example, dimethylam inoethylam ine, d iethyLaminopropyl amine and dime thyLam inopropyL aminee 1$ are also skuitabLe as the component Low-moleqular amines are used in most cases as the components It is also possible, however, to use highermoleu~armonoaminoas., A secondary amines are preferably used as the components Z0 in many cases several different amines are used as the component The positive charges required for water diLutability and capacity to be electricaly deposited m~y be inmparted by Orotonatijon with water-sot~ubLe acidt (for example boric 12 acid, formic acid, Lactic acid and, preferabLy, acetic acid) and/or by the use of amine saLts as the components in the binder molecuLe.

The cat ionic amine-modified epoxy resins used accordini to the invention are essentiaLLy free from epoxide groups, i -e their epoxide group conllenL i s s o L ow t h at c ro ss L inking reactions via the epoxidle groujps cannot take pLace either before or after the deposition of the, p a int f iLm The cationic amine-modified epoxy resini, used according to the invent ion pref erabLy do not conta in ny f ree epox ide groups.

The cationic amine-modified epoxy resins may beused both .as non-seLf-crossL inking res ins and as seLf-crossL inking re si1n s. Se~f-crossLinking cationic amine-mod ified epoxy r es ins may be obtained, for Lxample, by chemical modif ica-' K Hon of the cationic amine-modified epoxy resins. A selfcrossLink ing cat ionic amine-modif ied epoxy resin may be obtained, for example, by reacting the cat ionic aminemodified epoxy resin with a partly blocked poLyisocyanate aO which has on average one free isocyanate group per moLe~qute and whose bLocked isocyanate groups Lose their bLocking groups ony at elevated temperatures.

Preferred etectrodoating baths are obtained when non-$el crass (inking cation ic am ire-modlif ied epoxy res ins atre used asresint capabLe of being cathodiCaLLy depo~ited in Comib inatlion with a suitable tr'isL nkinig agent, 13 Examples of suitable crosst inking agents a re phenoplasts, poLyfunctional Mannich bases, melamine resins, benzoguanam ine re,-,ns, blocked poLy isocyana tes and compounds containing at least two groups of the general formula R-0 C0-~ The radicaL Rdenotes; R- R 20C0-QHz-, R 3 CHOH-CH 2 R 4 -C HO0R 5-C HH-C H2- I'R a Lky L R H, aLkyle R 6-H2 or R-C0-0-CH 2 R 4 H oralky( 0C 2 R H, a~kyL or ary( R 6 a~kyL, cyr.LcaLkyl or aryL K Preferred eLec'trocoating baths are obtained, when blocked if ifpolyisocyanates and/or compounds conta ining at Least two groups of the generaL formula R 1 -0-CO- are used as crossL inking agents, Any pQlsocyl-nateg in which the isocyanate groups have been react~d with a compound in such a way that the b~ocked poLy isocyana to formed~ is non-rqact iVe toward K-.droxyL and amino groups at room temperature, but becomes reactive 8t elevated temperatures, usua((y in the range from about 9 0 0C to about 300 0 (e may be used as the bloqked potyisocyanates. Any organic po~yisocyaetates suitable for xice oyscaae. Iocaae otilg~bu the e.rossLIn~k ing may be f or the preparation of the 44 4, 44 .4 4 4 49 4 4 *4 4 9 44 4 9*4 444* 44 44 9 4 4 0 9.444.

9 4 944* 4 44 44 *444 4 94 14 3 to 36, in particuLar about 8 to about 15 carbon atoms, are preferred. Examples of suitable di isocyanates are he imethylenedi isocyanate, 2,4-toLuyLenedi isocyanate, 2,6t, nediisocyanate and cyanato-1,3,3-trimethyLcycLohexane. However, it is also possible to employ poLyisocyanates of higher isocyanate functionality. Corresponding examples are trimerized hexamethyLenedi isocyanate and trimerized isophoronedi isocyanate. in addition, mixtures of polyisocyanates may 10 also be used. The organic polyisocyanates which are suitable as crossl inking agents for the invention may also be prepoLymers derived, for example, from a poLyol including a poLyether polyoL or a polyester poLyol.

Any suitable alipbatic, cycLoaLiphatic or aromatic aLkyl- 15 monoalcohoLs may be used for the blocking of the polyisocyanates. Examples of these are aLiphatic alcohols, such as methyl, ethyl, chLoroethyL, PropyL, butyl, amyL, hexyL, heptyL, octy. nonyL, 3,3,5-trimethyLhexyL, decyL and .aury( alcohol; cycloaiphatic alcohols such as cycLopentanoL and cyclohexanol aromatic alkyLaLcohoLs such as phenyLcarbinoL and methylphenylcarbino(.

Other suitable bLocking agents are hydroxyLamines such as ethanoLamine, oximes such as methyl ethyl ketonoxime, acetone oxime, and cycLohexanone oxime or amines such as dlibutylamine and diisopropylamine. The above poLyisocyanates and bLocking agents may also be used, in svitable proportions, for the Preparation of the partly blocked 4 The se f i Lms we re then ove rcoa ted by a c omme(r c:i aL aqueous 15 polyisocyana tes referred to above.

ExampLes of compounds wh ich contain at Least two groups 1 of the generaL formula R are bis(carbalkoxymethyl) azeLate, bis(carbal(koxymethyL sebacate, bis- (carbaLkoxyrnethyL) adipate, bis(carbaLkoxymethyL) dlecdnate, bis(carbaLkoxymethyL terephthaLate, bis(2-hydroxybutyl aceLate (sic) and bis(2-hydroxyethyL) terephthalate.

The crossL inking agent is usually used in an amount f rom to 60 X by weight, preferably 20 to 40 Zby weight, 1Qbased on the totaL amoun t of c ross Li nkabL e res in c apabL e 4 4 ofbeing cathodically deposited contained in the eLectrocoa ting ba th.

It is an essentiaL part of the invent ion that in the process according to the invention. eLectrocoat ing baths are empLoyed which contain at Least 7.-5 y we ig ht o f a poLyoxyaL kyL enepolyam ine or a mixture of several po( yoxyalkyLenepoLyamines of different chemical structures, the Percent age by weight referring to the total anioun t of binders contained in the oLectrocoating bath.

The poLyoxyaLkyLenepolyam ines are understood to be coinpounds which contain both oxyalkyLene groups as weLt as at Least two amino groups, preferably at Least two primary amino groups. The poLyoxyaLkyLenepotyamines should. have a number average molecular weight of about 137 to 3600, preferably 400 to 3000, ParticularLy preferabLy 800 to 16 2500. Furthermore, the poL yoxyaL kyL enepoLyam ines shoul d have an amine equivalent weight of about 69 to about 1800, pref erably 200 to 1500, part icul arly pref erabl y 400 to 1250.

The poLyoxyaLkylenepotyamines preferably used have a c-hemicaL structure according to the generaL formuLa (1) ri 2 N-CHR-CH 2-0- -CHR-CH 2 -C H 2

CHR-N-{

2 4a 4 :oyxak~neo~aie whnc whichhmi srctr 415 fr dte preporatin aof adclo ths to 6 carbyeneon amns ar aicoe nteptn xm~s4 1 n o1 in dcnotesnce wit 60, preeab al 20 (140: a, el -HC C4 -(41(H -H2r- -~2-HC a -1? in which

V

11 3 n m denotes 5 to 60, preferabLy m denotes 1 to 59, preferabLy n denotes 1 to 59, preferabty 20 to 5 to 5 to 4 44 4 4.

*4 4 4.

4 4 44 4 4 *44 4,4.

4 4 44.4 44

S

444444 4444 44 44~ 4444 4 *44 I t is aLso poss ibl e to use poLyo yaLky'Lenepoty'am ine der ivatives which are obtainable by the reaction of the poLyoxyalkylenepoLyamines described in us-Ps 3,236,895, column 2, Lines 40-72, with acrylonitriLe, followed by 10 hydrogeniat ion o f t he reac t ion produc t.

These derivatives have a chemical structure in accordance with the general structural fo-muLa (I II E 2 N- C H 2 3 -N CH-;I 2 -0 C R C 2 -0 n -C 2 C H R N H C -NH2 i n wh ic h R denotes H or an aLkyl radical of 1 to 6 carbon atoms, preferably

-CH

3 n denotes 5 to 60, prefereabty 20 to *~It goes w ithout saying that the etectrocoating baths used Saccording to the invention may also contain a mixture of L ~11~3~ 18 several poLyoxyalkyenepoLyamines of different chemical structures.

The polyoxyalkylenepolyamines or the polyoxyalkylenepoLyamine mixtures may be incorporated in the eLectro- S coating baths at any time during the preparation and even to the finished electrocoating baths. The pokyoxyalkylenepolyamines or the poLyoxyalkylenepoLyamine mixtures are preferably added either to the aqueous dispersion or a pre- 4,4, *cursor of the aqueous dispersion which contains a resin capable of being cathodically deposited and, optionally, a crosslinking agent and other :ustomary additives such as, for exampLe, antifoams etc. (cf. page 4, Lines 19 ff), or to the pigment paste or a precursor of the pigment paste (cf. page 4, Lines 26 ff).

The polyoxyakyenepolyamine molecules are in all proba- 4 bility protonized by the acid contained in the aqueous 4*44 dispersion or the pigment paste.

However, it is also possible to add the corresponding polyoxyaLkyenepolyamine or poLyoxyalkylenepolyamine mixture in thi protonized form to the aqueous dispersion under discussion or a precu'sur of this dispersion, or to the pigment paste or a precursor of the pigment paste.

The protonized polyoxyakyenepoLyamtne or polyoxyalkylenepolyamine mixture may be obtained by the simple addition of a Bransted acid to the corresponding polyoxyalkylenep Lyamine or polyoxya L kyLenepoLyamine mixture. The total 19 amount of Br6nsted acid contained in the finished electrocoating bath should be selected in such a manner that the pH of the electrocoating bath is between 4 and 8, preferably between 5 and It is 6n essential part of the invention that the amount of polyoxyalkylenepolyamine or polyoxyalkylenepolyamine mixture contained in the electrocoating baths used according to the invention is at least 7.5 X by weight, the ,t t i' percentage by weight referring to the total amount of 10 binders contained in the electrocoating bath. This means in other words that the electrocoating baths used accordiI ing to the invention must contain at least 7.5 parts by weight of polyoxyalkylenepolyamine or polyoxyalkylenepolyamine mixture per 100 parts by weight of binder.

When electrocoating baths with a lower content of polyoxyalkylenepolyamine or polyoxyalkylenepolyamine mixture are used, the resultant paint films exhibit considerably more and/or considerably more strongly pronounced surface defects than when the electrocoating baths accordi 20 ing to the invention are used.

The upper l iit of the amount of polyoxyalkylenepolyamine or polyoxyalkylenepolyamine mixture contained in the electrocoating baths used accordirg to the invention is determined by the plasticizing effect of the added polyoxyalkylenepolyamine or polyoxyalkylenepolyamine mixture 4 and is generally from 20 to 40 by weight, the percent- 11 age by weight referring to the total amount of binders rrr 9 9 9.

9 L .9

I

j 3 I I 20 contained in the eLectrocoating bath.

The electrocoating baths used according to the invention preferably contain 8 to 18, particularLy preferably to 15 by weight of polyoxyalkyenepoLyamine or polyoxyalkylenepolyamine mixture, the percentage by weight referring to the total amount of binders contained in the electrocoating bath.

The total amount of binders contained in the electrocoating bath is determined by adding the amount of resin capable of being cathodicaly deposited contained in the electrocoating bath, the amount of crosslinking agents optionally containtd in the electrocoating bath, the amount of ground resin contained in the eLectrocoating bath and the amount of resins which crossl ink under the baking conditions which may or may not be additionaLLy present in the electrocoating bath.

The solids content of the eLectrocoating baths used according to the invention is preferably 7 to 35 parts by weight, particularly preferably 12 to a5 parts by weight.

The electrocoating bath is brought into contact with an electrically conducting anode and with the eLectritaaLy conducting substrate connected as Cathode. When electric current passes between the anode and the cathode, a highly adherant paint film is deposited on the Cathode.

9 .'~iC

K/I

21 The temperature of the electrocoating bath should be between 15 and 35°C, preferably between 20 and The applied voltage may fluctuate within a wide range and may be, for example, between two and one thousand t 5 volt. However, typical operational voltages are between and 500 volt. The current density is usually between about 10 and 100 ampere/m 2 The current density tends to drop in the course of the deposition.

SWhen the deposition is completed, the coated object is rinsed and is then ready for baking.

V The deposited paint films are generally oaked at temperatures from 130 to 200°C during a period of 10 to minutes, preferably at 150 to 180 C during a period from 15 to 30 minutes.

The process according to the invention may be employed i for coating of any electrically conducting substrate, in particular, however, for coating Jf metals such as steel, K aluminum, copper and the l ke.

The invention is explained in greater detail in the exampl :s below. All parts and percentages are parts and percentages by weight, unless expressly stated otherwise.

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*I a i" 22 1. Preparation of aqueous dispersions containing a resin capable of being cathodically deposited and a crosslinking agent, 1.1 Preparation of an amine-modified epoxy resin 1780 g of Epikote 1001 280 g of dodecylpheno and 105 g of xylene are placed in a reaction vessel and molten at 120 0 C in an atmosphere of nitrogen.

Traces of water are subsequently removed in a slight vacuum. 3 g of N,N-dimethylbenzylamine are then added, the reaction mixture is heated to 130"C and kept at this temperature for about 3 h until the epoxide equivalent weight (EEW) has risen to 1162. The mixture is then cooled and 131 g of hexylglycol, 131 g of diethanolamine and 241 g of xylene are then added in rapid succession. This causes a slight temperature rise. The reaction mixture is then cooled to 90 0 C and further diluted by the addition of 183 g of butylglycol and 293 g of isobutanol. When the temperature has dropped to 700C, 41 g of N,N-dimethylaminopropylamine are added, the temperatur( is kept for 3 h and the mixture is then discharged.

The resin has a solids content of 70.2 and a base content of 0.97 milliequivalents/gram.

An epoxy resin from Shell with an epoxide equivalent weight of 500.

w/ I i L L 23 1.2 Preparation of a crosslinking agent 1.129 g of toLuyLene dfisocyanate (commercial mixture of isomers consisting of the 2,4 and 2,6 isomers) and 490 g of methyl isobutyt ketone are placed in a reaction vesseL in an atmosphere of nitrogen. 0.6 g of dibutyltin diLaurate and then, in small portions, 290 g of trimethylolpropane are added with stirring in such a manner that with external cooling the internal temperature does not exceed 50 0 C (duration about 2 h).

*r I The reaction mixture is further stirred, while cooLing, until the NCO equivalent weight has reached a value of 215. 675 g of ethylene glycol monopropy ether are then added dropwise at such a rate that the internal temperature does not exced 100C. The temperature is then kept at 10 0 C for 1 h, the mixture is diluted with 3642 g of methyl isobuty ketone and g of n-butanol, and after brief cooling the mixture is discharged. The resin has a solids content of 71.8 X (1 h at 130 0 C) and a viscosity of 1.5 dPas (50 X solution in methyl isobuty ketone, measured in a plate- one viscomoter).

1.3 Preparation of the aqueous disoersions 1.3.1 Dispersion (I) 915 g of resin according to proCeds re 1.1, 493 g S of crosstinking agent according to procedure 1.Z and 134 g of a polyoxypropyLenediamine of the formuLa 24- H 2 NCH(CH 3 )-Cd 2 (-OCH 2 -CHQH X -NH 2 x =33. 1 (JeffamineR 0 2000, commer~ia( product from Texaco ChemiqaL company) are mixed at room temperature and stirred. As soon as the solution has become homogeneous, g of qn antifoam so~ution 1 and 22 q, of gLacia( acetic acid are stirred in, and 674 g of deionized water are added in 6 portions.

The mixture is then diluted with fujrther 960 g of deionized water added in sniaU. portions, The resuLtant aqueous dispersion is freed from (owboiling solvents by Vacuum disti(Lation and subsequentLy diluted with deionized water to a iolids contqmt of 33 1,3.2 Dispersion (111) The procedure 1,3.1 is followed, except that 67 g of poLyoxypropylenediamine are used in pLace of 134 g of oQLyoxypropylenedlamite.

1SurfynoL (Commercial Product from Air Chemicals), a 50 t stength soLution in ethyLene SlycoL monobutyl other 1.3.3 Dispersion (111) Procedure 1.3.1 is foLtowed, excqpt that no potyoxypropyLenediamine is used. After vacuum disti(- Lat ion a correspondfingty smaLLer amou~nt of de ionized water is added in order to adjust the soL ids content o f 3 3 'Zb.

2. Preparation of a Pigment Paste 2.1 Preparation of a ground resin according to DE-OS 3,42Z,457 640 parts of a dig()c cdyl ether based on b isphenoL A and epich(orohydrin with an epoXidq eqivaLent weight of 485 and 160 parts of such dig~yc idy( ether w ith an epox ide qiu iva ten t we ight of 189 are mi xed a t IQOQC, par ts of 'Rxane thyL enediqm ine are p( aced in a f urther vessat hea ted to 1006r and t rea ted w ith 720 par ts of h- above hot epoxy res in m Ix ture in the Course of one hour, gentLA Coo( ng be ing necessary in order to k eep the temperature a t 1000 C. A fter a fur the per iod of 3U m inutes the excess hexamothy( Oee'140 ine is removed wh ite increas ing the tem~erazu~e and redue Ing the pressure, a f ina( teimporature of and a f inaL pressure of 30 mbar be inq reoc~ed- parts of stear Ic 4Cifds 172.i7 part$ of dimer ii fatty a4 id and 115 parts of xyLeone are then added. The water formed is then removed by azeotrop ic dist iLLion at to 180 0

C

in the Course of 90 m i. 5 8 orts o f bu t yiL9L yCo and if 26 322 parts of isobutano( are then added. The product has a so~ids content of 70 X and a viscosity'of 2240 mPas, measured at 75 0 C in a p( ate-cone v iscometer.

Z.2 Preparation of the pigment paste 586 parts of the ground resin are thorough~y mixed with 116? parts of deionized water and 22 parts of g~aciaL acetic acid. The mixture is subsequent~y treated with 880 parts Qf Ti102, 2 50 parts of an extender based on aluminum s iL ioate,. 53 parts of Lead s iL ieate and 10 parts of carbon bLack, This mixture is comminu~ted in a grinding unit to a Hegman fineness of Less than 12 Pm, Deionized water i s then added in order to reach the requ ired pas te consi1 stqney 3. Prepara tion of etcct rocoa ting ba th s and depos ited coatings according to the invention 700 parts of the pigment paste accord ing to procedu~re 2.2 are added to 2200 parts by weight of the dispersilons a ccord i rr to p roceOdwre 1 .3 anad the s6(lds Content of the bath is adjusted to 20 b y weig9h t uS i n g ce0- 0 ~ionized water4 The deposition of the paint, f iLms is carried out for 2 minutes at 300 V on~ phospha ted meta( sheep;. The bath temperature is 27C The I iL's are baked at 1656C for, 20 minutes.

Electrocoating bath 1: ELectrocoating bath 2: 27 Dispets ion according to procedure 1.3.1 wich paste according I;o procedure 2.2 PoL YoXYProp~yLenediamine conter t (based on~ the total amount of binders): 11,9% by weight Dilpersion ocs'ordlirg to procedure with paste a ,ording to procedure 8.Z PoLyoxypropv~ernecljamine content (ba ed on the tot4L amoujnt of binders): 6.0 by weight Dispersion according to procedure 1.3.3 with paste according to procedure Z.2 Po yoxyp ropy( ened iamni,,e content: o by weight t ELectrocoating bath 11: ,Depo'sit ion rsuL t8 ELectrocoat ing bath FiLm thickness, (tim) F iow-ou 1) Cr3 ters/dnA2 Z 7 2 20 2, 3 16 11.5 I IP-~l -j 26 These films were then overcoated by a commercial aqueous filler and a white alkyd topcoat, and tested in a condensed water static test for 240 h. The adhesion of the films was subsequently tested by the crosshatch test and the Tesa puLL-off test.

Electrocoating bath 1 2 3 Adhesion 0.5 0.5 S/ Rating 0 5 (good poor) I

Claims (7)

1. A process for coating electrically conductinga- substrates comprising immersing the substrate in an aqueous electrocoating bath which contains a resin capable of being cathodically deposited, connecting the substrate as cathode, depositing a film on the substrate by the action of direct current, removing the substrate from the electrocoating bath and baking the deposited paint film, wherein the electrocoating bath contains at least 7.5% by o weight of a polyoxyalkylenepolyamine or a mixture consisting of several polyoxyalkylenepolyamines of different chemical structures, the percentage by weight referring to the total amount of binders contained in the electrocoating bath, a S I,

2. The process as claimed in claim 1, wherein the Selectrocoating bath contains a cationic amine-modified epoxy S2"1 resin as the resin capable of being cathodically deposited. S3, The process as claimed in claim 1 or 2, wherein the electrocoating bath contains a polyoxyalkylenepolyamine of the general formula (I) 1 H 2 N-CHR-CH 2 -O-(-CHR-CH 2 -O-)n-CH2-CHR-NH2 (I) in which R denotes H or an alkyl radical of 1 to 6 carbon atoms, preferably -CH 3 n denotes S to 60, preferably 20 to

4. A substrate coated by the process according to any one of claims 1 to 3, An aqueous electrocoating bath containing resins 4 30 capable of being cathodically deposited, wherein the said bath contains at least 7.5% by weight of a polyoxyalkylene- polyamine or a mixture of several polyoxyalkylenepolyamines of different chemical structures, the percentage by weight referring to the total amount of binders contained in the electrocoating bath.

6. An electrocoating bath as claimed in claim containing a cationic amine-modified epoxy resin as the resin capable of being cathodically deposited. 7, An electrocoating bath as claimed in claim 5 or 6, containing a polyoxyalkylenepolyamine of the general formula H 2 N-CHR-CH 2 -O-(-CHR-CH 2 -O-)n-CH 2 -CHR-NH 2 (I) R denotes H or an alkyl radical of 1 to 6 carbon atoms, preferably -CH 3 n denotes 5 to 60, preferably 20 to

8. A process for coating electrically conducting g substrate'substantially as hereinbefore described with 21 reference to any one of the foregoing examples.

9. An aqueous electrocoating bath containing resins capable of being cathodically deposited substantially as hereinbefore described with reference to any one of the foregoing examples. Dated this 4th day of September, 1991 BASF LACKE FARBEN AKTIENGESELLSCHAFT By its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia PAT 88 169 04.12.1987 Abstract Process for coating electrically conducting substrates, substrates coated by this process and aqueous electro- coating baths The invention relates to a process for a cathodic electro- coating process, wherein the electrocoating bath contains ft I ft at least 7.5 by weight of a polyoxyalkylenepolyamine t or a mixture consisting of several polyoxyalkyenepoly- amines of different chemical structures, the percentage by weight referring to the total amount of binders con- tained in the electrocoating bath. INTERNATIONAL SEARCH REPORT International Application No PCT/EP 88/01164 1. CLASSIFICATION OF SUBJECT MATTER (If several classification symoois apply, Indicate all) According to International Patent Classificaion (IPC) Of t0 both National Classification and IPC Int. (l C 09 D 3/58; C 09 D 5/44

11. FIELDS SEARCH4ED Minimum Documentation Searcried Classification System I Cassificatior, Symbols Int.C1 4 C 09 D Documentaioni Searched other than Minimum Documentation to the Extent that such Documents are Included In the Fields Searched Ill, DOCUMENTS CONSIDERED TO 31 RELEVANT' Category I Citation of Document, 11 with Indication, wnerea pproplriate, of the relevant Passages it Relevant to Claim No, 13 A iDE, A, 3518770 (BASF) 1 27 November 1986 cited in the application A EA, 0070550 (PPG INDUSTRIES) 1 26 January 1983 cited in the application US, A, 4423166 A {EP A, 0200397 (ICI) 10 December 1986 A1, iO A, 86/07083 (BASF) 4 December 1986 A IWO, A, 86/05196 (PEINTURES CORONA) 1 12 September 1986 *Special categores of cited documentat in later document published aht the international ning date "A4 document defining the general state of the art which as not or priority dat*eand not In conflict with the application but c..niderd t be f paticlar elevncecited in1 ujdarstand the Principle or theory underlyIng the sqrllr documerrt but Published an or after the International docume nt of particular relevance: the claimed Invention filing date Cannot be considered novel or cannot be considered to IL' documentm which may throw doubts on priority claim(s) or invotve an Inventive step Which Is cited to estabtish the Publication date of another "'"douetfpriclreevnlthcamdivein c~ta~onor oherspe~al easn (e spcifed)cannot be considered to involve an inventive step when the docume~nt referring to an oral disclosure, use, ehibition or document Is combinied with one of more other such docu" other fiveno Monte, such combination being obvious to a person skilled documrent Published Prior to the International fI'lIng date but In the art, later than the priority dae claimed dorcument Member of the ijaivi patontj family I V, CER11TIFICATION Date of the Actual CompletIon of the International Search Date of Mailing of this International Search R600.3 21 March 1989 (21.03.89) 21 April 1989 (21.04, 89) International Searching Authority Signature of Authorized Wa'tr EUROPEAN PATENT OFFICE Form PCTI1SAIIO (second sheet) (ilinimry im6) ANNEX TO THE INTERNATIONAL SEARCH REPORT ON INTERNATIONAL PATENT APPLICATION NO. EP 8802264 SA 26712 This annecx lisv, the patent family' members relating to the patent document,; cited in the abo'.e-mentioned international search report. The Pe,-ecnb'ers are as contained in the European Patent Office EDP file on 12/04/89 The Eupopea Patent office is in no Aa), liable for these particulars v~hich are rnerel given for the purpose of information. Patent document Publication Patent family Publication cited in search report date member(s) date DE-A- 3518770 27-11-86 WO-A- 8607083 04-22-86 EP-A- 0241476 22-10-87 JP-'T- 62502899 19-11-87 US-A- 4780524 25-10-88 EP-A- 0070550 26-01-83 JP-A- 58025326 15-02-83, AU-A- 8545982 32-03-83 AU-B- 532421 29-09-83 US-A- 4420574 13-'2-83 US-A- 4423166 27'-12-83 US-A- 4432850 22-02-84 JP-A- 59127560 06-07-84 CA-A- 1283644 05-03-85 EP-A- 0200397 05-22-86 GB-A- 2273802 22-10-86 AU-A- 5595886 06-22-86 JP-A- 62276827 06-12-86 LU-A- 86837 07-12-87 WO-A- 8607083 04-12-86 DE-A- 3528770 27-11-86 EP-A- 0241476 21-10-87 JP-T- 62502899 19-11-87 US-A- 4780524 25-10-88 Wa-A- 8605296 12-09-86 EP-AB 0193685 10-09-86 AU-A- 5459186 24-09-86 JP-T- 62502976 06-08-87 US-A- 4689132 Z5-08-87 IFor mere detaiIk about this annex me Official Journal of tht European Patent Office, No. 12182