CA2069726A1

CA2069726A1 - Aqueous dispersion of a cathode-deposited binder, and a method of manufacture and use thereof

Info

Publication number: CA2069726A1
Application number: CA 2069726
Authority: CA
Inventors: Karl-Heinz Stransky; Wilfried Collong; Manfred Eder; Hans-Peter Patzschke
Original assignee: Individual
Current assignee: Axalta Coating Systems Germany GmbH and Co KG
Priority date: 1991-05-28
Filing date: 1992-05-27
Publication date: 1992-11-29
Also published as: JPH05171074A; EP0516066A2; DE4117417A1; EP0516066A3

Abstract

Herberts Gesellschaft mit beschrankter Haftung A b s t r a c t An aqueous dispersion of a cathode-deposited thermosetting cationic film-forming binder, manufactured by heating a slurry of the binder, used in the form of powder having a particle size of 0.1 to 1000 µm and a glass transition temperature of 35 to 130°C
a) in water, if the binder contains cationic groups, or b) in water and acid, if the binder contains cationic and/or basic groups, to a temperature of 40 to 90°C, for 5 minutes to 5 hours, a method of manufacturing the dispersion, and use thereof for cathodic deposition coating.

Description

~ ) ~

2~972~

Hexberts Ge~ellschaf~ mit b~chr~nk~r Ha~tung An aqueou~ ~3pcr~ion ~ a ~thoa~-~epo~ited bin~er, an~ a ~et~ of m~nu~ ur~ a~ U3~ t~er~o~' The invention rel~te~ to aqUeous dispersions o~ càthode-depo~ited, ther~nosetting film-forming binderEi fc;~ ooatin~
an electri~ally conductiv~ s~bstratR conne~ted as cathode.

thodic elec~rodeposit~on coating is a known method of læ.cq~e:ring electrically condu~ ive surfaces, e.~. surfaces o~ metal or electrically corlductive pla:tics or electrica~ly ~onductive lacqu~r layers. In t~e method, the ~acquer con~ituent~ ar~ pracipitat~ad ~rom an elea~rodepo~:ition bath on to the s~rfa¢e of a workpi~ce connected a~: c~h4d~, usin~ direct current~ The coagula~ed lacquer con3~ikuents ~re ~en liquef ied and c:~osslinXed by hea$1ng to ele~ated temperatures. The re~ul~ homo~en~ous smooth film wi~h high meahanical and ¢hemical stability. The p~po~e of the ~ilm is to prote~t the su~strate ~rom mec~anical damage and cor~osion.

The usua~ method of producin~ e~ectrodepositioh baths is to tran~p~r~ liquid or pa~ty water-containin~ or ~o~vent-containin~ mat~rial~, e.g. binder disp~rsions r pi~ment pa~tes or sol~ent-containing pigm~nt and bind~r mixtures, to the co~ing installation, whe~e these pre~pr~ducts ~re diluted wi~h water ~o obtain the electrodeposition ~ath ready ~or use. After ho~o~enisation, the e~eatro-depositio~ bath ~an be used for coating.

In this method, it is necessary to transport large guantities ~$ water and liquid ~inders, si~e bind~r disp~rsions must have onl~ a relativ~ly low cont~n~ of - 2~69726 ~olids i~ they are to have the l~w viscosi~y required for proce~slng~ If an accident occurs during transport ~f ~e~ thinly viscous material~, there is a ri~k that the s~rroundin~ earth will ~e contaminated~ If ~olvent-containing system~ ~e txansporte~, the volu~e tr~nsported i5 smaller and th~ viscos~ty somewhat hiyh~r, but~owing to tbe ~ig~ content of ~olvent the environmental poliution i~
even worse in the event of an accident during txan'spo~t~
It is al~o uneaonomic to ~ransport large guan~ities o~
water, which are needed only fc)r the sa}ce c~f sta~ility and ~iSGo~ity .
,~
Other Xnown electrod~po~ition baths contain powder ¢onc~ituents. All these çlectr~depo~$~i~n bath~, howeve~, ~h~ist largely of free-flowin~ th~nly ~iscous electro-depositio~ co~ti.ng ~inders. The start~ng materials are mixed wi~h water by th8 manufacturer and deli~er~d in the ~orm of ~ dispersion or frcely 10wing paste to thc u~er, where they are ~dditionally diluted with water. These ~ystems also are uh~conomio and ri~ky during transport~

DE la$d-~pen spe~i~ication 15 71 083 desçribe~ ~yste~s consisting ~f ~no~cally deposited liquid binders and t~e~moplastic powder~. The mixture of liquid anodic binders, ~round pla~tic~ powder J pigmentC and additional solvents is addi~ionally diluted with wate~ to p~od~ce ~h~
coating agent. EP laid-open speci~ication 0 05~ B31 describes cathode-depo~ited electrodeposition coa~ihg agents consisting o~ a~thode-deposited liguid ~inder~ and p~lver~lent i~nic pla~tics h~ing ~ glass tr~nsi~ion temperature ~ 300~, ~he plastics are solid and ~elt ~t elevated tempe~atures, but a free-flowing XTL binder is f ~L' ~l~p~aitio~ ~d to o~t~ a atablo b~th.

~E laid-open speci~ication 2Z 48 836 likewise describes ~athode-deposited electrodeposition coating age~ts ~ 2~S9726 ~prising one or more Cationic reBinS and a hon-ionic pla~tic~; pow~er. The catic:~nic resin is liçluid and optiohally c:ontain~; or~anic ~olvents. The el~:t~o-depoxition ba~h ~ ~ u~ed for ooating at temperature~ of e. g. 30~:.

DE laid-open speçifi~t~on 26 S0 hll ~escri~es electro-phoretiaally deposited coating agents c:on6~i~3tin~ ~f non-ionic plastics powders, optional pigments and a liguid polyme~ which is soluble or disper~ible in water or di~xol~ed in solYents. ~he resulting ele~trophoreti~ally qepos~table lacquers are deposited by k~own method~
temperatures be~ween 30 and 35~.

A common f ea~ure o~ these universally-known compo~itions of ele~tr~phoretically d~posita~le ~inde~ i8 th~t they need ~o ~ntain l~quid binder~ or binder ~olution~ in addi~i~n to the plastics powders, which are ~ d ~nde~
the deposition condit~on~.

~he composition~ a~e tran~ported either in on~ componen~
or in two di~fsrent component~ t~ the u~er. Thes~
components, o~ing tv the necessary e~se of ~ixing with wate~, are in a thinly-liqui~ or pasty state. The mixture~ can either be in solvent form, i.e. w~th a hi~h c~nten~ of organic solvents, or in aqueou~ for~. Even the aqueo~s f~rm, however, con~ain~ proportions o~ organic ~ lv~3nt3. The~e free- flowing substances tnUB~ be handled particularly carefully during t~ansport or refilling, sillce they will cause ~evere damage and danger to the environm~nt if they escape.

Another d~sad~antaqe of the hitherto-known methods is that in order to obtain a suita~le pumpable, ~h~nly-flowing consistency, considerable qUantities o~ organic ~o~vents (up t~ 50%) or up ~o 70~ water i~ needed. These ~. ~

~.

r~ ~
2~g~726 unnece~s~rily incr~a~e the volu~e ~or t~ansport. Al~o, some of th~ con~ention~lly used organic ~olvents adv~rsely affec~ th~ c~rod~po~it~on ha~h. The~e constituents may need ~o be remo~ed ~rom the ba~h and subsequently dumped in a safe manner.

The aim of the ~n~ention is to provide a method of cathodic electrodepocition which c~n be carrie~ oUt w~h b~nders which are safe and cause l~tle pollution and enable the ~e~uired v~lume tran~ported to ~e reduced to a mlnimum~

~his pr~blem i 5 s~lve~ ~y ~ ~a~hode-deposited electrodeposition material which i~ manuf~c~ured a~d delivered to t~e consumer in p4wde~ ~orm~ It has ~een ~ound tha~ a pulYerulent material o~ this kihd, after di&persing in water, optionally with additional known la~uer a~lt~Ves, op~lonally u6ln~ di~per~iny equip~ent, and h~ting ~f the aqu~ous dispersions, can be u~ed to obtain clcctrod~position baths ~ich are free from liquid ~ilm- ~o~mlng ~inders or binder solutions and are suita~le for ele~trodeposition ~oating.

The in~ention t~erefore ~elate~ to aqueous di~persions o~
one or mor~ cathod~-deposited thermosetting cati~nic fil~-~ormin~ binder~, characterise~ in that they are ~anuf~otured ~y heating a ~lurry ~f the binder or binders, u~ed in the form o~ powder haYing a particle size o~ 0.1 to 1000 ~m and a glass transition tempeXature of 35 to 130~

a) in wa~er, ~ t~e binder~ cont~in c~tionic ~roups, or b) in water and acid, if the binders contain cationi~
and/or basic ~roup~, to a tempexatu~e of 40 to gO~, for 5 minutes to 5 hours~

- 2~72~

q~he dispersions accordin~ to the lnvention a~
~ub~tantially ~ree ~rom l~quid or dissolved binder re~ins can }~e used to Goat an electrically conduc~iv~
substrat~ con~eated a~ ca~hode. ~oatings from the di~pex~ion~; u~ed as ele~::trod~o~ition ~aths can be obtained at tempe~atu~es o~ 20 to 80C.

According to the invention, pulverulen~ binder~ cc~nt~ining cationic g3~oups can be used in c~rd~3r to avoid ~ran po~t of liquid or pasty materials ~rom the binder manufacturer to ~h~ user, and t~u~ avoid the r~sulting econom~c di~advant~ges and pollution o~ thc ~3nviroP~en~.

Th~ pulv~rul~n~c binder~ u3ed in the dispe~sion~ acco~dinq t~ the invention a~e resins in powde~ ~orm which are solid und~r the condltions of ~anu~acture and transport ~ut melt at higher tempe~tures and ~ox~ a sm~oth f ilm . They are not cro~61inked whe~ in powder for~. They contain cationic ~roups or basi~: group~ convertible into cation~c:
group~, an~, are therefore dispcrsible ~nd remain ~table in the aqueous p~as~ ~t tempe~atu~es of 40 to gOC. T~e r~sins are usually not ~is~;olved in a true solution in the a~[ueous phase.

Optionally other conventional lacqu~r additives an~
constituents can be dispe~sed in the p~wders, e.~.
pigments, fillers, catalysts and other convention~
adjuvantc. The quantity o~ ~id necessary for neutr~lisation can als~ ~e distributed in the powders The~3e acid~3 ~re usually or~anic acids such ~s a~etic acid t formic acid, ~ulphamic a.cid, beh~oi~ acid or 1 actic acid.
q`he small ~uantities reguired can be àispersed without di~ficulty in the solid organi~ phase, so that even when the ac~ liquid the pvwder ~orm does~ not change.

Alternatively the resins conta.in~.ng p~ erulent CatiQr~iC

- ~ 206~726 or basic ~roups c~n be p~epared without additives, and pigmehts and optionally acid~ an~ othe~ additive~ and ~djuv~n~s can be added if nece~sary in the form of a conventional agueous pigment paste t~ the electro-deposition bath.

The disper~ion or the eleatxodepo~ition coa~iny agent i5 prepared ~rom the pulverulen~ starting material, op~lonally wl~n a pl~ment paste, a~ter ~llutlon Wlt~
water, optionally wi~h a~di~ion of aci~. To this end an aqueous s~urry i~ prepar~d ~n~ is prefer~bly ~oht~nuo~sly homogeni~ed, e.g. ~y vigorous ~gi~ation or pumping, and heated to a temperature of 40 to 90~, p~eferably over 60~. The ele~trodeposition ~ath i~ then ~eady for Goating~ at a temperature between 20 and 80C. A~ter dispersion, the ~ubstance can be ~ooled and re-he~ted fo~
d~p~sition~ The eleotrodepo~i~ion ~aths can be adjusted by the conventiona- adjusting agents.

The pulverulen~ resin~ used are powders having a particle size of 0.1 ~m to 100 ~m, preferably 2 to 40 ~m. CoarR~
poWder with a particle size o~ 100 to 1000 ~m may al~o be used. The par~i~le siZe of ~he powder will ~epend on the production facilities. Fine~y d~v$ded powder tends to produ~e more dust when poured. If equipment iS ava$1able for preventing ~he spread of du~t, the powder can have a par~icle siz~ of Q.l to 100 ~m. In oth~r cases, it i5 recommended to have a particle size of 100 ~o 1000 ~m.
Ano~hex possibility of avoiding dus~, which is ~npleasan~
and ~n explo~ion risk, i~ to produce powder slurri~s, e.g ~y a~itating 20 to ~0% by weight o~ powder, particle size 0.2 to 15 ~m, in 80 ~o 40~ by weight ~f deminerali~ed e~r~ p~slBnthiJ~n~n~u~yt~ f~
thixotropic, i~e. not liquid, and the~efore cannot pene~ate into the surroundin~ earth to any extent in the 8 2 ~72 6 event of ~n accident during tran~port. The pul~erulent resins have c~tion~ groups o~ basic group~ convertible into ~tiOhi~ grDUp~, so as to make the pulverulent re~ins di~per~ible in w~ter. The ~asic group~ are e.g. primary, secondary or ter~iary amino groups, ~hereas the cationic qroups ar~ ~g. quaternary nitrogon or qua~ernary~
phosphorus or tertiary sulphur atoms. These groups are firmly b~nded to the resin. rhe ~esins also cont~in reactive groups capable o~ arosslinking reactions, e.~. OH
groups, blocked N~ groups, p~mary ~d/or second~ry amino ~roups, SH groups, group~ o~pable of transesterification and~or gr~ups crosslinkable by Michael addition. The crosslinka~e groups can occur individually or in mixtures~

To give the pulverulent ~u~stance5 suffi~eht ~ta~ility in storage, the powdçrs mUst not coagulate. This i~ helped by the high gla~s transi~ion ~empe~a~Ure of the pow~er~, which is measured by the Differential S~nning Method, DSC, and is ovex 350C, pref~rably over 45~C. The uppe~
limit of the gla5s transi~ion temperature ghould be 130C, prefe~ably 100~, to ensure that the powders lique~y an~
~orm a smoo~h sur~aae ~ur ~ ng stoving.

~oagula~ion of the powders can be redu~e~ or prevente~
e~. by incorporating pi~ents by dispersion.
Alternatively the ~round binder powders can be surf~ce-treated with non- sticking organic or inorganic addit~ves. For example ~he powdex~ can be sur~ace-trea~ed with highly di~persed ~ilicic a~id. The resulting powdexs ~emain free-flowin~ and storable for a p~ticularly long time~

T~e p~lverulent cationi~ qroups or resins convertible into cationic groups can be ca~hode-depositea ~inders or mixtu~es thereof. These bind~rs ~an b~ self cro~slinXing , 20~9726 or extern~lly c~o~linked. In the case of ext~rnally cro~slinked binderq, cros~lin~ing agents c~n be added to the bin~er~ or ~inder mixture~ to obtain a chemi cally c~rosslinkable filr~. The c~ntent of cro~slinking agent in th~ powder can contain ionic groups. Alternatively it may be free from ionic groups, pr~vided it is us~d in~small proportions of less than 40% ~y weight r~lative to ~he total weight of binder. ~he binder components ne~ "ot individually h~Ye the ~tated gla~ transi tion ~empe~atures, par~i~le ~i~e~ and ionic g~oUp5. :s~t iS
sufficient if the mix~ure of film-forming r2sins or the mixtllre thereof with oro~link~ng agen~s meet~ the aiorementioned specif ications overall .

The pow~ers are e.g. amino epoxy resins obtained from poly~l~cidyl ethers with more than 1, preferably at le~st ~.S, epoxy ~roup~ per molecule, a~ter reaction with ami~e~
or compound~ o~ntaining ~ino g~oups. Polymex.
containing cationic or ~a~io gro~ps dnd ~ormed from ole~inical~y uns~turated polymerisabl~ monomers may also be used, AminP epox~ re~in~ are pre~erred. As mentioned, the bind~rs contain crosslinkable ~u~ctional gro~ps sueh as OH groups, blo~ked N~O groups, primary and~or s~condary amino groups, S~ groups, group~ ~apable of tran~-estexification and~or groups crosslinka~le ~y M~ahael addition, pre~ent individuall~ or in mix~ures.

The ~esin.~ used in th~ powders are preferably ~ho~e conYentionally provided for ~athodic el~ctrodeposition coatin~, such as tho~e h~therto use~ in liquid systems, e.g. a~ solutions ~ dispersions. The powders ~d~ ~e ~roduced from the liquid systems by removal of the ~olvents, o.~. by distillation and op~ional subsequen~
grinding. They can also be prepared in the melt and grouhd ~fter cooling. The b~5ic resins used in the powde~s can e.g. be amino epoxy re~ins or resin~

206~726 containing ami~o y~oup~ and obtaine~ by polymerisat~on o~
un~aturated monomers. The resins pre$e~ab1y have an amine nu~ber of 45 to 120 mglg KOH and a hydroxyl number o~ 50 to 400 mg/g KOH~

Examples of basic resins used in the powders are ~escribed in ~he l~id-open specifications EP O 08Z 291, EP O 234 395 ox EP ~ ~09 587. The resins prepared ~herei~ by ~
dissol~in~ in org~ic solvents can be ~onverte~ into powder ~y removing the solvent, e.g. by di~illation ~e.g.
i~ a thin-laye~ evapor~tor) and subsequent grinding. The s~bstances are amino epoxy resins b~sed on glycidyl ethers with more thah 1 epoxy group per molecule, preferably ~a~ed on ~i~phenol A or novGl~k and containing conventional primary, ~econdary and/or tertia~y ~mino ~roups. The amine number i~ usually between 45 and 120.
The amine nu~er oan be used to in~luence the di~persi~ility of the resin powder, and also t~ influence the quality of the. surface of ~he crosslink~d film o~
la~uex. If the ami"e number is too sm~ll, the resins canno~ disperse sufficient~y and do not form a ~t~ble di~persion. If the amine num~e~ is too high, the re~ult i~ a poor surface with inadequate prote~tion a~ainst cor~osion. These r~ins have OH group~ ~ additio~ to amino ~roup~. The hydroxyl number is preferably about 50 to 50V. ~l~ne acclve nyaroxyl ~oups~ ~y~ Pr wl~
reactive amino group~, are responsible f~r ~rosslinki~g.
Their num~er is preferably at ~ea~t 2, and particularly preferably ~t least 4 per molecule. ~r ~he de~ree of crosslinking of the ~ilms forme~ from the powders is too low, the films have poor mecha~ical p~operties after cro~slinkin~ the degree of crosslinking is ~oo high, the cros~linked ~ilms are brittle.

Other functional ~roup~ can be introduced e~ by reac~in~
OH or NH ~roups in the ~e~in mol~cules w~th isocyAnate~

- 2~72~

c~ntaininy the required fun~tional groups. If conventional semi-capped diisocyanate~ are used as the reaction component, ~el~ osslinking bin~ers are p~oduced via capped isocyana~e group~. O~her functional group~ can ~e introdu~ed, e.g. via ~meth)acrylic acld derivatives.
~h~ resulting ~inder~ will then con~ain ~, ~-unsat~u~ated carb~yl ~roup~. The binders can opt~onally b~ modified w~th other ~unctional groups. Anoth~r method o~ ~ynthesis i5 descri~ed e.g~ in EP-o OS~ ~31, where functionalised amino epoxy resin~ are produced in s~lid ~ol~ent~free form. ~or ~xample, epcxy resins i~ ~he melt are reacted ~ with ~mino ~lcohols and further processed in the mel~, optio~ally after solidifying to powder.

Other example~ of ~ros~linkable binders usable in the powders ~re de~cri~ed e.g. in EP-O ~61 385. These substance~ also ar~ resins dissolved ~n org~ni~ sol~en~s and conYertlble in~o powder as previously described~ ~hey ar~ polymers obtainable by polymerisation of radiaally polymerisable un~a~urated ~onomer~, at least part of which have ~unctional groups ~uitable for dissolvin~ or cros~linkin~ For exa~ple u~e can be made o~ saturated ~trai~h~-c~aih or branche~ a~ryli~ or ~et~c~ylic ~id esters, glycidyl ~m~th~ acrylates, allyl glyci~yl ethers, ; vinyl ether~, styrene, hydroxy ~meth) acryl~t~s or oth~r ~unctionali6ed aarylic acid an~/ox methacxyl~c a~c~d derivative~. Amino groups necessary for ~olubility can ~e ~ntroduced e.g~ by reactin~ epoxy yroups with secondary amine~ or amino alco~ols, o~ can be incorparate~ ~y p~lymerisation via compounds containing am~ no g~oup~ .

~he glass t~ansition temperature can be influenced via the nature of the monomers. The ~onomers can also be used to adjust the ~umber o~ crosslinkable group-~.

A~ mentioned, the.pulverulent res~ hS can be self-20~72~

crossli~king or externally crosslinXed. ~he follo~i~g resins are ex~mples of ~uita~le cro~xlinkiny agents:
~iazine resi~s, alkoxy methyl (~QthJ ac~ylic ami~e copolymers, blocked isocyanates, res~ns capable of trans-ssterification or tran~amidation, resin~ with ~ermin~l d~u~le ~onds or cros61inking agents capabl~ of Mic.hael reac~ion. Cxosslinking agentS of thi~ ki~d are curre~t in the literature and aescribed e.g. in EP l~id-open -~pecification 0 245 7~6, DE 34 36 345 or DE 37 1~ ~05 These ~ub~tance~ also ~re resins di~olved in organic solven~s ahd converti~le into powder ~ previousl~
described. In s~e c~ses they can also be produced in ~he substance and pulverised. The powders can ~ uni~o~m or in the form of mixture~ The individual powder parti~les can be homogeneous or he~erogeneou~ ~ixtures ~an ~e prep~red ~y ~ixing pr~fabri~ated powder p~rticles to~ether ana opllonally grlnu~ IU~ ~lL~lla~lV4'y ~lJ~y ~
manu~actured by processing mixed solutions until they are free from solvent and grinding them. Pre~erably the work is car~ied out so that al~ the powder particles have ~onic groups. If for example a non-ionic resin is used, it can bo proc4~0Qd with ~n lnni~ r~Rin tn nhtA;n he~.Rrn~P.nP.nu powder particles having ionic char~es.

Resin~ prod~ced in organia solvents are converted into ~
~orm containin~ little or no ~olvent. A low-solvent ~orm has a solven~ content which can be used to obtain a non~
sti~ky powder with a glas~ transition te~peratUXe of 35 to 130~. Alte~natively the Pinders can be p~oduced solvent-free, e.g. in the melt, ~nd th~n converted $nto powder.

Additive~ and pi~men~s can be contained in the powder~
~hey can be added at any time before y~inding. For example they can ~e added to solid re~ins Xor grinding or to a resin already in solution before the sol~e~t has ~een remo~ed. After removal of ~he ~olven~, the res~n~, 13 20~9726 optionally containing additive~; and pigmsnts, are ground to ~he necessary f ineness in a suita~le apparatus. T~e conte~t o~ solvents c)r licr4id constit:uent~ mus~ be so low ~h~t the resulting pow~ers do not co~gulate and can ~till flow freely afte~ ~ prolonged period. Suitable grinding appar~tU~ and ~ethods o~ grinding powder~ are known and freguently described in the ~iteratur~.
..
Small quantities of organic or inorganic acid~, e.g.
~or~i~ acid, ~cetic acid, l~atic acid or ~lkyl phosphoria acid, are ne~essary to neutralise the binder or to ~orm cationic groups. The acids used aan be li~uid or ~olid, e.g. ben80ic acid, sulphamic ac~d or ~lycolic acid.
~ptionally, polybasic ~cids ~uch as c~tric acid or ox~lic acid can al~o be usedO A~id anhydrides or ea~ily h~dr~lysed este~ oan ~lso be ad~ed. The follo~in~ are exampl~ thereof: acetic acid anhy~ride or maleic a~i~
anhyd~i~e or p-toluene~ulphoni~ acid meth~l e~ter. If the ne~tralising ~gents are added via the po}ymer powder, solid neutralising a~ent~ are pre~erred~

Suitable pigTnents can al60 ~e incorpora~ed in the polymer powders containing ionic groups. The pigments can e . ~. ~e titanium dioxide, carbon bl~k, organia or inor~anic po~dered dyes, fine~y-divi~ed filler~ such as highly-dispersed silicic acid, p~lverulent catal~sts or anti-corrosion pigments such as lead ~ilicatès.

The fillers can also be polyme~ micropart~¢le~ which do not melt under the sto~ing conditions. Cros~lin~ed polymer micropa~tiGles are preferred. The poly~er microparticles sho~ld preferably not ~ontain any ionic g~oup6 on the surface. Cationic groups, however, may be present on the surfa~e. They must be sufficlently crosslinked not to li~uef~ with the bind~r when stoved.
~L ~ h~ld b2 ~ 20 ~m, prn~ar~ly ~ m.

:

2~6~72~

~hey can b~ inc~rpora~ed like normal pigments ~n the binde~ or the pigment pa~e~. The pDlymsr particle~ may op~ion~lly carry surface unctional group~ such as OH, SH
or ~ster group~. These can react wi~h the b~nder during stoving. ~he po~ymer m~¢roparticles can ~e manu~actured e:.y. Vll ~ 1~ v ' ~ ~GL~ ~r r~~
or p~enol ~ormaldehyde resins.

The pi~m~nts a~e ~inely dist~ibuted in the binders in known manner, e.g. ~y ho~ageneously mixing ~he binder with the pigments in a sultable ~ixer, e.~. an extruder. The mixin~ process ~n also ~e assi~ted by elevated temp~rature. The mixt~e o~ binder and pigment is then commin~ted ln known apparatu~ ~nd ground to the necessary~
fineness in a mill . ~he pigmen~ particles are then ~o~ted with ~he polymer po~der and have a sultable particl~ size distribution.

Th~ pulverulent resins ~ontain~n~ ionic groups and ~ed a~cordinq to the lnvention can al~o be pro~uced without a~ding a pigment. In that aase a clear l~cquer ~oating is .
o~tained after deposition and ~toving. In another method, the binders are added in the ~'orm of pu~verulent pigment-free resins to the electrod~position ba~h and the pigmentsare a~ded to the b~t~ after ~eing prepared sepaxately~

The piqment preparat~ons can be obtained from ~onventional pi~ment paætes, produced by grindin~ pigments with wetting ~gents qr "paste resins" (binders used in ~rinding). For example EP laid-open specifi~ation O 183 025 describes pa~te resins based on epoxy resins with par~i~lly reacted oxazoli~in~ rings. The ~itation also des~ribes how pi~meht pastes are produ~ed ~rom ~he aforementioned binders ~oget~er with conventional pigment~. ~he pigmeht ~ C~ ~c~ h~ Llon elh~llld profr~hl ~
be aq~eous. They can be p~epared by the user and added to 2 ~ 2 6 th~ di~persion~

The pigment pa~tes are added in a proport$on of 0 to 20, preferabl~ O.5 to 20 partQ per 100 part~ o~ bind~r powder, preferably 2 to 10 parts. Owing to t~e s~all quantity, they cannot form films by themselves. They C:~n ~e ~o3.u~le or dispersible in Wate~. They can contain ionic groups or ~Q present without ionic ~roup~. Preferably they~ontain functional groups which can ~eact with the film-f~xming resin~ rhe paste binders should be p~e~ent in aqueoug disp~rsion and ~ontain only ~mall propo~tion~ of solvent.

Th~ paste resin~ are e.g. ~inders based on epoxy resin~, al~yd ~e~ln~, polyurethane resins or polyether~.
Non-~onic paste binder~ ~an also be prepared, e.g. base~
on a s~ralgn~-Gna1n or ~r~ u ~y~ y~ yly~v polypropylene glycol wi~h or ~ithout terminal gr~fted ethylehe ~xide compon~nts.

~xamples of pa~e re~ins are de~ri~ed e . g . in EP
pen specification 0 108 088~ EP O ~83 0~5 or EP 0 ~?0 877. They ar~ wettin~ agents or binders having a high capacity to wet pigment~ and ~iller~. ~hey should be easily co~npatible with the binder in the a~ueous coating agent ~nd should not al~er the properties of the binder mixture. They can optionally become crossli~ked with the binder ~ia functional group5. These pa~te xesins h~ve basic ~unction~l groups which, when neu~ralise~l with ac$d, make the paste.re~in~ disp~rsible in waterO
Alternati~ely, partly-re~cted catio~i~ functional groups m~y be present ~n the paste re~ins. Example~ o~ ~uch fun~tional ~roup~ are quaternary nitro~en atoms, quaternary phosphorus ~toms or ~ertiary sulphur 9TOUpB.
The sol~bility of the paste binders ~ 5 influenced via the number of these neutralised or ionic group~7 20~972~

T~e numb~r of cationic group~ can ~e so high that the pa~te re~ins c~nnot be ~epo~ited on the catho~e ~y themselves, i.e. do not produc~ a homogeneous uni~Drm fil~.

Preferably the paste resins have functiona~ groups for crosslinking to th~ ~ilm-formin~ resins, e.g. prim~ry or ~econd~ry OH ~OUp~, ~ea~t~ve amino gr~up-~, e~tet~qrollp~
capabl~ of tran~e~te~ification or c~pped l~o~yanate~, met~ylol groups or alkoxym~thyl groups, pr~ferably methox~me~hyl groups~

Piym~nt paste resins based on ~odified epoXy resins can be used e.g~ i they contain at least one, preferably at lea~t two epoxy group , where 50 to ~00 mol % of ~he free epoxy ~XOUp5 are rea~t~d with ~ prim~ry-ter~iary diamine, the ~x~ess epoXy groups are optionally previously reacted with sQconda~ or primary amine, and 80 to 100 ~ol % of the secondary amino groUps present have been re~cted with a car~onyl compound to form oxazo~idine structures. The~e binding agents can be converted into a~ a~ueou~ dispersio~
~y adding an acid. The molec~lar weight o~ ~he modif ied epoxy r~sin~ ~hould be 400 to 10000. The hydroxyl num~e~
:~nOUla De ~ l~U my r~ullt~ ~L'I~ ~' a~y ~ lVU IU~ n/y~
content of ~rga~ic solvents sh4uld be below 30~.

Example~ of u~ble non~ionia pa~te re~in~ ~r wetting ~gents ~e descri~ed in DE laid-open spec~iaations 30 18 715, 36 ~1 6~g and 26 0~ 831. They are no~-ionic re in aomponents which should have a good capacity to wet pigments an~ fillers~ They ~ust be eas~ly compatible with th~ binder system of the aqueous ooating agent and must not alter the proper~ies of the binder o~ binder mixture.
It is adv~ntageous i~ these pa~te binders can rea~t via ~unctional ~roups with the binder in the aqUeQUs coating agent. These non-ionic paste resins have good solu~ility 17 2 ~72 in w~te~. They ~annot be deposited at the ~hode by ~hemse}v~s, but only togPther with the ~inder system.
Samples of such substances are polyalXylene glycols.

Alternatively, non-ionic pa~te resins c~n be derived from epoxy re~ins, preferably from aro~ati~ epoxy resi~s which have been made more soluble in water vi~ polyethyiene oxide or polypropylene oxide component3, or alter~atively .
the non- ionic pa~te resins can be non-ionic wetting agents based on melamine or phenolic resin.

Pigment pastes can ~e made from the known paste xe~in~.
For exa~ple demiheralised water ca~ be added to the paste resin, opt~onally after it has been ne~tr~li6ed wi~h an a~id and thus made ~ispersible in water. Pi~ent~, fil~ers, ~atalys~s, anti-corrosion pigments, inorganic or organic colour pigments and othe~ additives a~e added to the thin-~lowing mixture. The additi~es are, for example, anti-foaming agent~, wetting ~gents, le~ellin~ agents or anti-crate~in~ a~ents. After th~ mixture has been thoroughly hom~genised, the viscosity o~ the pigment pa~te is ad3usted with c4mple~el~ dem~heral~Sed water, foilowed by grin~in~ ~o the necessary finene~s ~n ~ con~entional grinder~ e g. ~ pear~ mill. Th~ resulting pi~m~nt p~stes are aqueou~, p~pa~le and have good stability in storage.

The ele~trodeposition coating agents used ac~ordin~ to the inVention can be ~anufactured as follows: the polymer powder, thoroughly agita~ed and ho~ogenised, i~ slow~y added ~o the amount of completely demineralise~ wa~er necessary for the electrodeposition ~oatin~ ~ath.

ca~e mus~ be taken ~hat the polymer powders do not coagulate but ~e~in ~inely dispersed. If the a~ueoug powder slurry does not ~low freely, i~ ~an be ~etered through a pump for thick matter. Op~onally a pigment .~ ~

18 2~63726 paste ~an be added, with tho~ough mixing, to the ~in~er dispersion. Alternatively the pi~ment~ c~n already be pre5ent in the pol~er powde~, or ~ pigment-free K~L
system can be used. Preferably the pigments ar~ dispersea in the polymer po~der when used~

Aft~r thoroug~ ~omogeni~tion, the ele~trodepositi4n coating bath is hea~ed for S minu~ex ~o 5 hour~.
Alternatively, homogeni3ation can ~e bro~ght a~out directly at t~e ~eposition temperature nf the ~ath. The heating t~mp~rature is about 40 to 90~, pre~erably 50 to 80DC, particularly prefer~bly 60 to 75OC. In the proce~
the bath is continuously homo~nis~d. Preferably the h~ating temperature is chosen from the prcviously-mentioned ~ange to mat~h the glass tranSition ~e~pe~ture of the binder powde~ u~ed, i~e. a moderate heAting te~perature ior a low glaas transition t~mperature and a hRn~,in~ t,Rm~r~tl~r~, frnm tlh~, uD~,r ~f~r~,~Rntinn~ r~nu nt. hi~h~ ~aa~ t~an~ n temue~atl~e~, ~he h~tinu temperat~re ~hould be chosen so ~hat it is not ab~ve ~he melting-point of the polymer used.

I~ the electrodeposition bath is used to top up an exis~ins ~ath, t~e pulverulent electrod~position lacguer and binder ~ompo~ition and optional}y the pigment paste ~ay also be dispersed in the exis~ing e~ectxodeposition bath. After h~ogeni~ation and heatin~ to elevat~d tompor~tura, ~h~ thnrli~ Q~ trnrl~l~n~;t inn hn1-h ~ rP~ly ~or coating.

~he cathodic electrodeposition bath is used fo~ coating at ~0 to 80DC, pre~erably 30 to 60~C. The ele~rodeposition coating agent is st~ble at these temperaturl3~ and does no~
~ecompose . The method according to the invent ion is o~
particular use e.g. for c:oating industrial products made . of ~netal, t:onductive plastic:s or electricall~r conduct~ng 7 ~ ~

lac~uer layers. T~e guality of the coatin-3s ~ill depen~l Oh the h2~ture of the products. Produots not expos~d to the weather, e . g . sl~elves, coated ~y the method can be given a di~ier~nt grade of powder from t~at U~;e~ f or car bodies, The powdexs used for washing-machines no~m~lly h~ve good resistanc~ to alkalis after stoving, in~ad~tion ~o ot~er import~nt prope~ties. ~he ranqe of indu~trial products wh~ch can be coated ac~ording ~o the invcntion is the same as for exi~ting elect~odeposition baths. Af~er deposition, the coatings have ~ood propertie~, i.e. good ~r~ rmlnn ~n~l ~rlh~inn ~.n t.h~ ~r~ace un~neath, coated parts are Purther treate~ in conv~n~ional manner, e.g. they are washed clean ~nd cro ~linked at ~levated te~perature. Wet-in-wet f~rthe~ co~ting is also possible.

Conventional ad~usting agents can be added to the electrodeposition coating agent~ according to the inventionn If necessary, for example, acid can sub~e~uently ~e add~d to the ~ath, i.e. the aforementioned acids conventionally used in elec~rodepo~ition coating.
Also, substances can be added to prevent the ~ath from foaming, or levelling agents s~ch a~ fatty alcohols containing 12 - zo car~on atoms, or ~u~tances for adjusting the l~yer thickne~s or anti- ora~ering additives if neces~ary, e.g. as described in D~-OS ~0 18 87fi. The resulting cathode-deposited electrodepo~ition coating baths give smooth level film~ a~ter crosslinXing. The edge~ have good properties as regards re~istanae to co~rosion or weatherinq. ~he coatin~ have good resis~ance to gravel.

The resultin~ C:o~tings on condu~tive metal substrates can b~ single layers, o~ alternativcly additional laye~ ~uch as fillers or cDvering la~quer~ can be applied to ~h~
primin~ layers. The resulting single-~ayer or multilayer coatihgs have a gDDd appearance.

2~72~

~he in~entio~ wi~l now be explained in detail with reference ~o v~riou~ exam~le~. All percentage6 are by weight~

~e~in a~mpl~

A. As per EP-B-0 012 463, 3~1 g diethanol~mine, 189 g of 3-(N,N-dimethylamino)-propylamine and 1147 g of an ad~uct fr~ 2 mol hexane diamine-1,6 and 4 mol gly~idyl ester of ver~ati~ ~c~d (cardur~ E10) wexe added to S~73 g bisphenol ~-epoxy resin ~poxide e~uivalent weight approx. 47~) in 3000 g of ethoxy propanol. The reaction mixtur~ w~s heated with agitation at 85 to 90~C for 4 hours and then ~ep~ at 120C for 1 hour. The solven~ was then distille~
off in vacuo in a thin-layer evaporator and ~he resulting ~in tg1A~ Ln~ n t!~:mpc~u~ ~ 40n) u~a a~minu~cd to a si~e of ab~t 5 m~ in ~ suitable apparatus.

B. 160 g of ~prolactam was ~lowly added with agitation at 70C to 453 g o~ a ~olu~ion of a ~e~ction product ~rom 3 mol isophorone diisocyana~e and 1 m~l trimethylol propane ~7~ in ethyl acetate). The reaction ~ix~ure was then kept at 70C until the NC0 content had fallen to zer4. ~he solvent was ~he dist~lled o~ in vacuo in a thin-layer evaporator and the resultin~ re~in ~glass transit~on temperature ~ 40~C) was ~o~nuted to a size of a~out 5 mm in a ~uitable apparatus.

~e resulting resins a~ per A and ~ were mixed in ~he ratio 8 : 2 (solids).

Pi~nt paste example 2:

A. g50 g o~ an epoxy ~esin based on bispheno~ A (2 epoxy equivalents) was d~ssolved in 633 ~ xylene ~nd added at 60 21 2~7~
~ ~OnQ t~ ~ ~ni~tsur-- ~t 100 y Q ~th~l h~x~l~ils~ ~
diethyl aminopro~yl ~mine. The t~mperature wa~ pt ~elow 75~. A~ter all t~e epoxy groups had ~e~an compl~ely us~d up, 59 g paraform~ldehyde (91%) wa~ added. The mix~ure wa~ heat~d until the ~eaction water had heen azsotropically ~o~d.

The xylene was then distilled off in a ~atch and the binder, af~er ~dding 780 mmol acetic acid per loO g solid resin, was dilu~ed with deionised ~ater to a solid ~ontent Qf 30%~

B~ 143 ~ of a commercial aluminium ~ilic~ta powder, 10 g carbon bla~k, 16 g pyrogenic silicic a~id and 8 g dibutyl tin oxide powder was added t~ 53 ~ o~ pa~ta resin A ~30%
in water) in a high~peed agitator. ~he solids wer~
ad~ust~d to a~out 44% -with 115 g completely demin~ralis~d wal,~ VUII~ y ~ y <,~
pigment paste~

Pigmont paste example 3:

125 ~ ~f a commercial N-butanol etherifi~d ~la~ine/
~ormaldehyde resin t75% sol ids in butanol, vi~co~ty 6500-6800 mPas) w~re ~i~ed with 24 g di~tyl tin oxide, 5 g carbon ~lack~ 160 g titanium dioxide and 35 g bu~oxyet~anol and gxound in A suita~le mill to a fineness ~elow 5 ~m.

Lacquer ex~mpl~ 4:

Po~dered resin as per example 1 was mixed ~ith 0.3%
dibutyl tin dilaura~e ~nd ground in a suitable mill to finenes~ below 25 ~m.

1.0 g of a co~mercial ~etti~ ag~n~ ~50%) and 5.5 g for~ic 2~9726 acid ~50~) wer~ add~d to 1000 g completely demineralised water. 150 ~ of the previously-descxi~ed binder powder was ad~ed with agitat~on. ~he ~a~h was ~ade up to 2000 g with ~o~pletely ~eminer~lised w~er. ~h~ ba~h wa~ he~ted to about ~o~c for 15 m1n~tes and agitatedA It remained stable and did not pr~cipi~at~.

L~e~W~ a~ a~tAw~olcw~r7no~ nu~ Q~ ~nll m~terial a~here~ firmly. The films o~ained after stoving had a ~od s~fac~ and a layer thickness of about 25 ~m and 20 ~m.

~acguer example 5:

A. lO g di~lltyl ~in ~xide, 3 g oxalic a~d, 7 g carbon bla~ and 30 g titaniu~ dioxide we~ added ~o S00 g o~ the bind~r mixture in exampl~ 1 and wer~ homogen~ou~ly mix~d in suitable apparatu~ and ~hen ground to a siz~ of les~
th~n 40 ~.

B. 7.~ ~ wettin~ agent (50S) was added to lOoO g completely dem~ne~alised water, ~ollowed by 120 g of the powder in A, with vigorous agitation. The bath was heated to 70C for 30 ~inuteæ and was then ready ~or coati~g.
T~e metal sheets wexe coated at 30~ and at 55C, wa~hed clean and then sto~ed a~ 180~C for ~0 minutes. The film~
had a thick~ess between 20 and 30 ~m and a good su~dce.

Laagu~r e~ample ~:-A clear la~quer was made from 5 g we~tin~ agen~, 7~5 gformic acid, 1000 ~ water and 150 g resin powder as per example 1 ~round to about 30 ~m). The lacquer was made up ~o ~uu~ g wlth w~t~r. ~ ~r ~idl l~v~ll;~y agent/butyl glycol ~l ~ l) waæ a~de~ and 132 g of a 2~972~

pigm~nt paste as per example 2. ThQ lacquer w~s h~ated to 600C and applied a~ter co~liny.

Lacouer examnla 7:
A clear lacquer wa~ made from S q wetting agent, 7.5 g ~ormic acid, 1000 g water and 150 g resin powdRr as per examplc 1 ~ground to a~ut lo ~m~. 4~ g of a pi~m~nt pa~te as per exa~pl~ 3 was ~dded to the mixt~re With ~igo~ agitation and th~ lacquer ~a~ heated to ~0C.
~he lacquer was diluted with ~000 g complRtQly de~ineralised water and ~ould be applied after cooling.
.

~cguer exa~ple 8:

A, 10 g dibutyl tin oxide, ~1 g ~ulphamic a~id, 7 ~ carbon blaa~ ~nd 30 g tltanium dioxide were added ~O
500 g of the binder mixture as per example 1, uniformly mixed in ~uitable apparatus ~d then ground to ~ 40 ~m.

R~ 7. 5 ~ wettin~ agent ~SO%) wa~ added to 1000 g c~pletely deminerali~ed water, ~ollowe~ ~y 120 g o~ the powder in A, with vigorous agitation. The bath wa~ heated t~ 7~c for 30 ~inute~ and w~s then ready for coating.
The metal sheets were coated at 30DC and It 55C~ washed clean and then ~toved at 180~ for 30 minute6. The film~
had a thickness betweeh ~0 ah~ 30 ~m ~nd a good surface.

.

Claims

1. An aqueous dispersion of a cathode-deposited thermosetting cationic film-forming binder, characterised in the it is manufactured by heating a slurry of the binder, used in the form of powder having a particle size of 0.1 to 1000 µm and a glass transition temperature of 35 to 130°C
a) in water, if the binder contains cationic groups, of b) in water and acid, if the binder contains cationic and/or basic groups, to a temperature of 40 to 90°C, for 5 minutes to 5 hours.

2. A dispersion according to claim 1, characterised in that the pulverulent binder used is surface-treated with non-sticking organic or inorganic additives.

3. A dispersion according to claim 1 or 2, characterised in that the binder consists of a mixture of binders, one or more self-crosslinking resins and/or a mixture of one or more externally crosslinking resins with one or more activators.

4. A dispersion according to claim 1, 2 or 3, characterised in that the pulverulent binder is made from solutions of conventional cathode-deposited binders in organic solvents by removing the solvent and subsequent pulverisation.

5. A dispersion according to claim 1, 2, 3 or 4, characterised in that the pulverulent binder has an OH number of 50 to 400 mg/g KOH and an amine number of 45 to 120 mg/g KOH, determined by primary, secondary tert. amino groups or quaternary nitrogen atoms, or instead of the amino groups has a quantity of quaternary phosphorus atoms and/or tert. sulphur atoms equivalent to the amine number, and a quantity of functional groups reactive with OH or NH and sufficient for crosslinking.

6. A dispersion according to any of claims 1 to 5, characterised in that the binder powder contains solid and/or liquid acid.

7. A dispersion according to any of claims 1 to 6, characterised in that the water used in manufacture contains conventional additives present in cathode-deposited baths and/or is mixed with the powder after it has been dispersed.

8. A dispersion according to claim 7, characterised in that the water used in manufacture contains the following additives and/or is mixed therewith after the powder has been dispersed:

fillers and/or pigments 0 to 60 parts by weight catalysts and/or acid 0 to 10 parts by weight paste resin for grinding fillers, pigments and/or catalysts 0 to 20 parts by weight additives and/or solvents 0 to 10 parts by weight in each case per 100 parts by weight of binder powder, the hinder powder and the additives being added or present in quantities such that the total solid content of the dispersion is about 5 to 30% by weight.

9. A dispersion according to any of claims 1 to 8, characterised in that the water used for manufacture is a cathode-deposited bath used for regeneration with the binder powder.

10. A dispersion according to claim 9, characterised in that the original composition of the bath to be regenerated corresponds to the composition of the dispersion according to claim 8.

11. A dispersion according to any of claims 8 to 10, characterised in that the additives are wetting agents, levelling agents and/or anti-foam agents.

12. A method of producing an aqueous dispersion of a cathode-deposited cationic thermosetting fiim-forming binder, characterised in that a slurry is formed from a binder powder having a particle size of 0.1 to 1000 µm and with a glass transition temperature of 35 to 130°C

a) in water if the binder contains cationic groups, or b) in water and acid if the binder contains cationic and/or basic groups and the slurry is heated to a temperature of 40 to 90°C for 5 minutes to 5 hours.

13. A method according to claim 12, characterised by use of a pulverulent binder surface-treated with non-sticking organic or inorganic additives.

14. A method according to claim 12 or 13, characterised in that the binder consists of a self crosslinking resin or a resin/activator mixture.

15. A method according to claim 12, 13 or 14, characterised in that the pulverulent binder is produced from solutions of conventional cathode-deposited binders in organic solvents by removing the solvent and subsequent pulverisation.

16. A method according to claim 12, 13, 14 or 15;
characterised in that the pulverulent binder has an OH number of 50 to 400 mg/g KOH and an amine number of 45 to 120 mg/g KOH determined by a primary, secondary, tert. amino groups or quaternary nitrogen atoms, or instead of the amino groups has a quantity of quaternary phosphorus atoms and/or tert. sulphur atoms equivalent to the amine number, and a quantity of functional groups reactive with OH or NH and sufficient for crosslinking.

17. A method according to any of claims 12 to 16, characterised in that the binder powder contains solid and/or liquid acid.

18. A method according to any of claim 12 to 17, characterised in that the water used for manufacture contains conventional additives present in cathode-deposited baths and/or is mixed therewith after the powder has been dispersed.

19. A method according to claim 18, characterised in that the water used in manufacture contains the following additives and/or is mixed therewith after the powder has been dispersed.

fillers and/or pigments 0 to 60 parts by weight catalysts and/or acid 0 to 10 parts by weight paste resin for grinding fillers, pigments and/or catalysts 0 to 20 parts by weight additives and/or solvents 0 to 10 parts by weight in each case per 100 parts by weight of binder powder, the binder powder and the additives being added or present in quantities such that the total solid content of the dispersion is about 5 to 30% by weight.

20. A method according to any of claims 12 to 19, characterised in that the water used in manufacture is a used-up cathode-deposited bath which is regenerated by mixing with the binder powder.

21. A method according to claim 20, characterised in that the original composition of the used-up bath corresponds to the composition of the dispersion in claim 8.

22. A method according to any of claims 19 to 21, characterised in that the additives are wetting agents, levelling agents and/or anti-foam agents.

23. A method aacording to any of claims 12 to 17, characterised in that the binder powder contains dispersed fillers, pigments and/or catalysts.

24. A dispersion according to any of claims 1 to 6, characterised in that the binder powder contains dispersed fillers, pigments and/or catalysts.

25. Use of the aqueous dispersion according to any of claims 1 to 11 and 24 for cathodic electrodeposition coating.

26. Use according to claim 25 for priming electrically conducting parts of motor vehicles.

27. A substrate with a coating obtained by use according to claim 25 or 26.

28. A method of electrodeposition coating of substrates, characterised by use of an electrodeposition bath containing an aqueous dispersion according to any of claims 1 to 11 or 27, or an aqueous dispersion prepared according to any of claims 12 to 23, and electrodeposition coating is carried out at a temperature of 30 to 60°C.